drm/panel: do not return negative error codes from drm_panel_get_modes()

None of the callers of drm_panel_get_modes() expect it to return
negative error codes. Either they propagate the return value in their
struct drm_connector_helper_funcs .get_modes() hook (which is also not
supposed to return negative codes), or add it to other counts leading to
bogus values.

On the other hand, many of the struct drm_panel_funcs .get_modes() hooks
do return negative error codes, so handle them gracefully instead of
propagating further.

Return 0 for no modes, whatever the reason.

Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Jessica Zhang <quic_jesszhan@quicinc.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: stable@vger.kernel.org
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/79f559b72d8c493940417304e222a4b04dfa19c4.1709913674.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drm/panel: Add a way for other devices to follow panel state

These days, it's fairly common to see panels that have touchscreens
attached to them. The panel and the touchscreen can somewhat be
thought of as totally separate devices and, historically, this is how
Linux has treated them. However, treating them as separate isn't
necessarily the best way to model the two devices, it was just that
there was no better way. Specifically, there is little practical
reason to have the touchscreen powered on when the panel is turned
off, but if we model the devices separately we have no way to keep the
two devices' power states in sync with each other.

The issue described above makes it sound as if the problem here is
just about efficiency. We're wasting power keeping the touchscreen
powered up when the screen is off. While that's true, the problem can
go deeper. Specifically, hardware designers see that there's no reason
to have the touchscreen on while the screen is off and then build
hardware assuming that software would never turn the touchscreen on
while the screen is off.

In the very simplest case of hardware designs like this, the
touchscreen and the panel share some power rails. In most cases, this
turns out not to be terrible and is, again, just a little less
efficient. Specifically if we tell Linux that the touchscreen and the
panel are using the same rails then Linux will keep the rails on when
_either_ device is turned on. That ends to work OK-ish, but now if you
turn the panel off not only will the touchscreen remain powered, but
the power rails for the panel itself won't be switched off, burning
extra power.

The above two inefficiencies are _extra_ minor when you consider the
fact that laptops rarely spend much time with the screen off. The main
use case would be when an external screen (and presumably a power
supply) is attached.

Unfortunately, it gets worse from here. On sc7180-trogdor-homestar,
for instance, the display's TCON (timing controller) sometimes crashes
if you don't power cycle it whenever you stop and restart the video
stream (like during a modeset). The touchscreen keeping the power
rails on causes real problems. One proposal in the homestar timeframe
was to move the touchscreen to an always-on rail, dedicating the main
power rail to the panel. That caused _different_ problems as talked
about in commit 557e05fa9fdd ("HID: i2c-hid: goodix: Stop tying the
reset line to the regulator"). The end result of all of this was to
add an extra regulator to the board, increasing cost.

Recently, Cong Yang posted a patch [1] where things are even worse.
The panel and touch controller on that system seem even more
intimately tied together and really can't be thought of separately.

To address this issue, let's start allowing devices to register
themselves as "panel followers". These devices will get called after a
panel has been powered on and before a panel is powered off. This
makes the panel the primary device in charge of the power state, which
matches how userspace uses it.

The panel follower API should be fairly straightforward to use. The
current code assumes that panel followers are using device tree and
have a "panel" property pointing to the panel to follow. More
flexibility and non-DT implementations could be added as needed.

Right now, panel followers can follow the prepare/unprepare functions.
There could be arguments made that, instead, they should follow
enable/disable. I've chosen prepare/unprepare for now since those
functions are guaranteed to power up/power down the panel and it seems
better to start the process earlier.

A bit of explaining about why this is a roll-your-own API instead of
using something more standard:
1. In standard APIs in Linux, parent devices are automatically powered
on when a child needs power. Applying that here, it would mean that
we'd force the panel on any time someone was listening to the
touchscreen. That, unfortunately, would have broken homestar's need
(if we hadn't changed the hardware, as per above) where the panel
absolutely needs to be able to power cycle itself. While one could
argue that homestar is broken hardware and we shouldn't have the
API do backflips for it, _officially_ the eDP timing guidelines
agree with homestar's needs and the panel power sequencing diagrams
show power going off. It's nice to be able to support this.
2. We could, conceibably, try to add a new flag to device_link causing
the parent to be in charge of power. Then we could at least use
normal pm_runtime APIs. This sounds great, except that we run into
problems with initial probe. As talked about in the later patch
("HID: i2c-hid: Support being a panel follower") the initial power
on of a panel follower might need to do things (like add
sub-devices) that aren't allowed in a runtime_resume function.

The above complexities explain why this API isn't using common
functions. That being said, this patch is very small and
self-contained, so if someone was later able to adapt it to using more
common APIs while solving the above issues then that could happen in
the future.

[1] https://lore.kernel.org/r/20230519032316.3464732-1-yangcong5@huaqin.corp-partner.google.com

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230727101636.v4.3.Icd5f96342d2242051c754364f4bee13ef2b986d4@changeid

drm/panel: Check for already prepared/enabled in drm_panel

In a whole pile of panel drivers, we have code to make the
prepare/unprepare/enable/disable callbacks behave as no-ops if they've
already been called. It's silly to have this code duplicated
everywhere. Add it to the core instead so that we can eventually
delete it from all the drivers. Note: to get some idea of the
duplicated code, try:
git grep 'if.*>prepared' -- drivers/gpu/drm/panel
git grep 'if.*>enabled' -- drivers/gpu/drm/panel

NOTE: arguably, the right thing to do here is actually to skip this
patch and simply remove all the extra checks from the individual
drivers. Perhaps the checks were needed at some point in time in the
past but maybe they no longer are? Certainly as we continue
transitioning over to "panel_bridge" then we expect there to be much
less variety in how these calls are made. When we're called as part of
the bridge chain, things should be pretty simple. In fact, there was
some discussion in the past about these checks [1], including a
discussion about whether the checks were needed and whether the calls
ought to be refcounted. At the time, I decided not to mess with it
because it felt too risky.

Looking closer at it now, I'm fairly certain that nothing in the
existing codebase is expecting these calls to be refcounted. The only
real question is whether someone is already doing something to ensure
prepare()/unprepare() match and enabled()/disable() match. I would say
that, even if there is something else ensuring that things match,
there's enough complexity that adding an extra bool and an extra
double-check here is a good idea. Let's add a drm_warn() to let people
know that it's considered a minor error to take advantage of
drm_panel's double-checking but we'll still make things work fine.

We'll also add an entry to the official DRM todo list to remove the
now pointless check from the panels after this patch lands and,
eventually, fixup anyone who is triggering the new warning.

[1] https://lore.kernel.org/r/20210416153909.v4.27.I502f2a92ddd36c3d28d014dd75e170c2d405a0a5@changeid

Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230727101636.v4.2.I59b417d4c29151cc2eff053369ec4822b606f375@changeid

drm/dp: Move panel DP AUX backlight support to drm_dp_helper

We were getting a depmod error:
depmod: ERROR: Cycle detected: drm_kms_helper -> drm -> drm_kms_helper

It looks like the rule is that drm_kms_helper can call into drm, but
drm can't call into drm_kms_helper. That means we've got to move the
DP AUX backlight support into drm_dp_helper.

NOTE: as part of this, I didn't try to do any renames of the main
registration function. Even though it's in the drm_dp_helper, it still
feels very parallel to drm_panel_of_backlight().

Fixes: 10f7b40e4f30 ("drm/panel: add basic DP AUX backlight support")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reported-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rajeev Nandan <rajeevny@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210712075933.v2.1.I23eb4cc5a680341e7b3e791632a635566fa5806a@changeid

drm/panel: add basic DP AUX backlight support

Some panels support backlight control over DP AUX channel using
VESA's standard backlight control interface.
Using new DRM eDP backlight helpers, add support to create and
register a backlight for those panels in drm_panel to simplify
the panel drivers.

The panel driver with access to "struct drm_dp_aux" can create and
register a backlight device using following code snippet in its
probe() function:

err = drm_panel_dp_aux_backlight(panel, aux);
if (err)
return err;

Then drm_panel will handle backlight_(enable|disable) calls
similar to the case when drm_panel_of_backlight() is used.

Currently, we are not supporting one feature where the source
device can combine the backlight brightness levels set through
DP AUX and the BL_PWM_DIM eDP connector pin. Since it's not
required for the basic backlight controls, it can be added later.

Signed-off-by: Rajeev Nandan <rajeevny@codeaurora.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>
[dianders: added blank line for warning when applying]
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1624726268-14869-2-git-send-email-rajeevny@codeaurora.org

drm/panel: Add helper for reading DT rotation

This adds a helper function for reading the rotation (panel
orientation) from the device tree.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200813215609.28643-2-digetx@gmail.com

drm: Remove unnecessary drm_panel_attach and drm_panel_detach

These functions are now empty and no longer
useful so remove the functions and their uses.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Bernard Zhao <bernard@vivo.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>,
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Icenowy Zheng <icenowy@aosc.io>,
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Robert Chiras <robert.chiras@nxp.com>
Cc: dri-devel@lists.freedesktop.org,
Cc: linux-kernel@vger.kernel.org
Cc: opensource.kernel@vivo.com
Signed-off-by: Sam Ravnborg <sam@ravnborg.org> # Fixed build and a few warnings
Link: https://patchwork.freedesktop.org/patch/msgid/9e13761020750b1ce2f1fabee23ef6e2a2942882.camel@perches.com

drm/panel: remove return value of function drm_panel_add

The function "int drm_panel_add(struct drm_panel *panel)"
always returns 0, this return value is meaningless.
Also, there is no need to check return value which calls
"drm_panel_add and", error branch code will never run.

Signed-off-by: Bernard Zhao <bernard@vivo.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200801120216.8488-1-bernard@vivo.com

drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

The initial commit followed by the fix didn't
take into consideration the case:

CONFIG_DRM_PANEL=y
CONFIG_BACKLIGHT_CLASS_DEVICE=m
CONFIG_DRM_I915=y

where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.

Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191217140721.42432-1-andriy.shevchenko@linux.intel.com

drm/drm_panel: fix EXPORT of drm_panel_of_backlight

Fix link failure for module builds of panels.
The conditional compilation around drm_panel_of_backlight()
was wrong for a module build.
Fix it using IS_ENABLED().

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Fixes: 152dbdeab1b2 ("drm/panel: add backlight support")
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20191210194758.24087-1-sam@ravnborg.org

drm/panel: drop drm_device from drm_panel

The panel drivers used drm_panel.drm for two purposes:
1) Argument to drm_mode_duplicate()
2) drm->dev was used in error messages

The first usage is replaced with drm_connector.dev
- drm_connector is already connected to a drm_device
and we have a valid connector

The second usage is replaced with drm_panel.dev
- this makes drivers more consistent in their dev argument
used for dev_err() and friends

With these replacements there are no more uses of drm_panel.drm,
so it is removed from struct drm_panel.
With this change drm_panel_attach() and drm_panel_detach()
no longer have any use as they are empty functions.

v2:
- editorial correction in changelog (Laurent)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Stefan Mavrodiev <stefan@olimex.com>
Cc: Robert Chiras <robert.chiras@nxp.com>
Cc: "Guido Günther" <agx@sigxcpu.org>
Cc: Purism Kernel Team <kernel@puri.sm>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-8-sam@ravnborg.org

drm/panel: decouple connector from drm_panel

To facilitate moving connector creation to display drivers,
decouple the drm_connector from drm_panel.

This patch adds a connector argument to drm_panel_get_modes().

All users of drm_panel_get_modes() already had the connector
available, so updating users was trivial.

With this patch drm_panel no longer keeps a reference to the drm_connector.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Alison Wang <alison.wang@nxp.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: CK Hu <ck.hu@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Cc: Sandy Huang <hjc@rock-chips.com>
Cc: "Heiko Stübner" <heiko@sntech.de>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Torsten Duwe <duwe@lst.de>
Cc: Vasily Khoruzhick <anarsoul@gmail.com>
Cc: Icenowy Zheng <icenowy@aosc.io>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Brian Masney <masneyb@onstation.org>
Cc: Rob Clark <robdclark@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Allison Randal <allison@lohutok.net>
Cc: Shayenne Moura <shayenneluzmoura@gmail.com>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-rockchip@lists.infradead.org
Cc: linux-tegra@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-7-sam@ravnborg.org

drm/panel: add drm_connector argument to get_modes()

Today the bridge creates the drm_connector, but that is planned
to be moved to the display drivers.
To facilitate this, update drm_panel_funcs.get_modes() to
take drm_connector as an argument.
All panel drivers implementing get_modes() are updated.

v2:
- drop accidental change (Laurent)
- update docs for get_modes (Laurent)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Stefan Mavrodiev <stefan@olimex.com>
Cc: Robert Chiras <robert.chiras@nxp.com>
Cc: "Guido Günther" <agx@sigxcpu.org>
Cc: Purism Kernel Team <kernel@puri.sm>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-6-sam@ravnborg.org

drm/panel: add backlight support

Panels often support backlight as specified in a device tree.
Update the drm_panel infrastructure to support this to
simplify the drivers.

With this the panel driver just needs to add the following to the
probe() function:

err = drm_panel_of_backlight(panel);
if (err)
return err;

Then drm_panel will handle all the rest.

There is one caveat with the backlight support.
If drm_panel_(enable|disable) are called multiple times
in a row then backlight_(enable|disable) will be called multiple times.

The above will happen when a panel drivers unconditionally
calls drm_panel_disable() in their shutdown() function,
whan the panel is already disabled and then shutdown() is called.

Reading the backlight code it seems safe to call
the backlight_(enable|disable) several times.

v3:
- Improve comments, fix grammar (Laurent)
- Do not fail in drm_panel_of_backlight() if no DT support (Laurent)
- Log if backlight_(enable|disable) fails (Laurent)
- Improve drm_panel_of_backlight() docs
- Updated changelog with backlight analysis (triggered by Laurent)

v2:
- Drop test of CONFIG_DRM_PANEL in header-file (Laurent)
- do not enable backlight if ->enable() returns an error

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-3-sam@ravnborg.org

drm/drm_panel: no error when no callback

The callbacks in drm_panel_funcs are optional, so do not
return an error just because no callback is assigned.

v2:
- Document what functions in drm_panel_funcs are optional (Laurent)
- Return -EOPNOTSUPP if get_modes() is not assigned (Laurent)
(Sam: -EOPNOTSUPP seems to best error code in this situation)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191207140353.23967-2-sam@ravnborg.org

drm/panel: Add and fill drm_panel type field

Add a type field to the drm_panel structure to report the panel type,
using DRM_MODE_CONNECTOR_* macros (the values that make sense are LVDS,
eDP, DSI and DPI). This will be used to initialise the corresponding
connector type.

Update all panel drivers accordingly. The panel-simple driver only
specifies the type for the known to be LVDS panels, while all other
panels are left as unknown and will be converted on a case-by-case
basis as they all need to be carefully reviewed.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190904132804.29680-2-laurent.pinchart@ideasonboard.com

drm/panel: Initialise panel dev and funcs through drm_panel_init()

Instead of requiring all drivers to set the dev and funcs fields of
drm_panel manually after calling drm_panel_init(), pass the data as
arguments to the function. This simplifies the panel drivers, and will
help future refactoring when adding new arguments to drm_panel_init().

The panel drivers have been updated with the following Coccinelle
semantic patch, with manual inspection to verify that no call to
drm_panel_init() with a single argument still exists.

@@
expression panel;
expression device;
identifier ops;
@@
drm_panel_init(&panel
+ , device, &ops
);
...
(
-panel.dev = device;
-panel.funcs = &ops;
|
-panel.funcs = &ops;
-panel.dev = device;
)

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823193245.23876-3-laurent.pinchart@ideasonboard.com

drm/panel: drop return code from drm_panel_detach()

There are no errors that can be reported by this function,
so drop the return code.
Fix the only bridge driver that checked the return result.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804201637.1240-14-sam@ravnborg.org

drm/panel: move drm_panel functions to .c file

Move inline functions from include/drm/drm_panel.h to drm_panel.c.
This is in preparation for follow-up patches that will add extra
logic to the functions.
As they are no longer static inline, EXPORT them.

v2:
- align order of functions in drm_panel.h and drm_panel.c (Laurent)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804201637.1240-12-sam@ravnborg.org

drm/panel: Small documentation polish

Need to make sure people can find the panel-bridge to avoid typing too
much.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111164048.29067-3-daniel.vetter@ffwll.ch

Revert "drm/panel: Add device_link from panel device to DRM device"

This reverts commit 0c08754b59da5557532d946599854e6df28edc22.

commit 0c08754b59da
("drm/panel: Add device_link from panel device to DRM device")
creates a circular dependency under these circumstances:

1. The panel depends on dsi-host because it is MIPI-DSI child
device.
2. dsi-host depends on the drm parent device (connector->dev->dev)
this should be allowed.
3. drm parent dev (connector->dev->dev) depends on the panel
after this patch.

This makes the dependency circular and while it appears it
does not affect any in-tree drivers (they do not seem to have
dsi hosts depending on the same parent device) this does not
seem right.

As noted in a response from Andrzej Hajda, the intent is
likely to make the panel dependent on the DRM device
(connector->dev) not its parent. But we have no way of
doing that since the DRM device doesn't contain any
struct device on its own (arguably it should).

Revert this until a proper approach is figured out.

Cc: Jyri Sarha <jsarha@ti.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180927124130.9102-1-linus.walleij@linaro.org

drm/panel: Fix sphinx warning

Resolves the following warnings.
../drivers/gpu/drm/drm_panel.c:158: WARNING: Unexpected indentation.
../drivers/gpu/drm/drm_panel.c:159: WARNING: Block quote ends without a blank line; unexpected unindent.

Fixes: c59eb3cfde1f ("drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled")
Cc: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180815203833.210143-1-sean@poorly.run

drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled

DT nodes might be present in the DT but with a status property set to
"disabled" or "fail". In this case, we should not return -EPROBE_DEFER
when the caller asks for a drm_panel instance. Return -ENODEV instead.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180509130042.9435-3-boris.brezillon@bootlin.com

drm/panel: Make of_drm_find_panel() return an ERR_PTR() instead of NULL

Right now, the DRM panel logic returns NULL when a panel pointing to
the passed OF node is not present in the list of registered panels.

Most drivers interpret this NULL value as -EPROBE_DEFER, but we are
about to modify the semantic of of_drm_find_panel() and let the
framework return -ENODEV when the device node we're pointing to has
a status property that is not equal to "okay" or "ok".

Let's first patch the of_drm_find_panel() implementation to return
ERR_PTR(-EPROBE_DEFER) instead of NULL and patch all callers to replace
the '!panel' check by an 'IS_ERR(panel)' one.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180509130042.9435-2-boris.brezillon@bootlin.com

drm/panel: Add device_link from panel device to DRM device

Add device_link from panel device (supplier) to DRM device (consumer)
when drm_panel_attach() is called. This patch should protect the master
DRM driver if an attached panel driver unbinds while it is in use. The
device_link should make sure the DRM device is unbound before the panel
driver becomes unavailable.

The device_link is removed when drm_panel_detach() is called. The
drm_panel_detach() should be called by the consumer DRM driver, not the
panel driver, otherwise both drivers are racing to delete the same link.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b53584fd988d045c13de22d81825395b0ae0aad7.1524727888.git.jsarha@ti.com

drm/panel: Remove drm_panel_detach() calls from all panel drivers

Remove all drm_panel_detach() calls from all panel drivers and update
the kerneldoc for drm_panel_detach().

Setting the connector and drm to NULL when the DRM panel device is going
away hardly serves any purpose. Usually the whole memory structure is
freed right after the remove call. However, calling the detach function
from the master DRM device, and setting the connector pointer to NULL,
has the logic of marking the panel again as available for another DRM
master to attach. The usual situation would be the same DRM master
device binding again.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/464b8d330d6b4c94cfb5aad2ca9ea7eb2c52d934.1524727888.git.jsarha@ti.com

drm/panel: Constify device node argument to of_drm_find_panel()

The argument is never modified by the function, make it const.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/panel: Flesh out kerneldoc

Write more complete kerneldoc comments for the DRM panel API and
integrate the helpers in the DRM DocBook reference.

Signed-off-by: Thierry Reding <treding@nvidia.com>drm/panel: Add helper for simple panel connector
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160506140137.GA4641@ulmo.ba.sec

drm: Add panel support

Add a very simple framework to register and lookup panels. Panel drivers
can initialize a DRM panel and register it with the framework, allowing
them to be retrieved and used by display drivers. Currently only support
for DPMS and obtaining panel modes is provided. However it should be
sufficient to enable a large number of panels. The framework should also
be easily extensible to support more sophisticated kinds of panels such
as DSI.

The framework hasn't been tied into the DRM core, even though it should
be easily possible to do so if that's what we want. In the current
implementation, display drivers can simple make use of it to retrieve a
panel, obtain its modes and control its DPMS mode.

Note that this is currently only tested on systems that boot from a
device tree. No glue code has been written yet for systems that use
platform data, but it should be easy to add.

Signed-off-by: Thierry Reding <treding@nvidia.com>