drm/mgag200: Add a workaround for low-latency

We found a regression in v5.10 on real-time server, using the
rt-kernel and the mgag200 driver. It's some really specialized
workload, with <10us latency expectation on isolated core.
After the v5.10, the real time tasks missed their <10us latency
when something prints on the screen (fbcon or printk)

The regression has been bisected to 2 commits:
commit 0b34d58b6c32 ("drm/mgag200: Enable caching for SHMEM pages")
commit 4862ffaec523 ("drm/mgag200: Move vmap out of commit tail")

The first one changed the system memory framebuffer from Write-Combine
to the default caching.
Before the second commit, the mgag200 driver used to unmap the
framebuffer after each frame, which implicitly does a cache flush.
Both regressions are fixed by this commit, which restore WC mapping
for the framebuffer in system memory, and add a cache flush.
This is only needed on x86_64, for low-latency workload,
so the new kconfig DRM_MGAG200_IOBURST_WORKAROUND depends on
PREEMPT_RT and X86.

For more context, the whole thread can be found here [1]

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/dri-devel/20231019135655.313759-1-jfalempe@redhat.com/ # 1
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240208095125.377908-1-jfalempe@redhat.com

drm: Only select I2C_ALGOBIT for drivers that actually need it

While working on a drm driver that doesn't need the i2c algobit stuff I
noticed that DRM selects this code even though only 8 drivers actually use
it. While also only some drivers use i2c, keep the select for I2C for the
next cleanup patch. Still prepare this already by also selecting I2C for
the individual drivers.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221219083627.1401627-1-u.kleine-koenig@pengutronix.de

drm/mgag200: Add support for G200 desktop cards

This patch adds support for G200 desktop cards. We can reuse the whole
memory and modesetting code. A few PCI and DAC register values have to
be updated accordingly.

The most significant change is in the PLL setup. The driver parses the
device's BIOS to retrieve clock limits and reference clocks. With no BIOS
found, safe defaults are being used.

v2:
* copy BIOS ROM to system memory and access with regular
load/store; resolves potential HW limitations
* fix some stray whitespaces

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Co-developed-by: Egbert Eich <eich@suse.com>
Signed-off-by: Egbert Eich <eich@suse.com>
Co-developed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730102844.10995-9-tzimmermann@suse.de

drm/mgag200: Replace VRAM helpers with SHMEM helpers

The VRAM helpers managed the framebuffer memory for mgag200. This came
with several problems, as some MGA device require the scanout address
to be located at VRAM offset 0. It's incompatible with the page-flip
semantics of DRM's atomic modesettting. With atomic modesetting, old and
new framebuffers have to be located in VRAM at the same time. So at least
one of them has to reside at a non-0 offset.

This patch replaces VRAM helpers with SHMEM helpers. GEM SHMEM buffers
reside in system memory, and are shadow-copied into VRAM during page
flips. The shadow copy always starts at VRAM offset 0.

v2:
* revert dev->pdev changes

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: John Donnelly <John.p.donnelly@oracle.com>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200515083233.32036-16-tzimmermann@suse.de

drm/mgag200: Fix Kconfig indentation

Adjust indentation from spaces to tab (+optional two spaces) as in
coding style with command like:
$ sed -e 's/^ /\t/' -i */Kconfig

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191120133625.11478-1-krzk@kernel.org

drm/vram: fix Kconfig

select isn't recursive, so we can't turn on DRM_TTM + DRM_TTM_HELPER
in config DRM_VRAM_HELPER, we have to select them on the vram users
instead.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190904054740.20817-8-kraxel@redhat.com

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drm/mgag200: Convert mgag200 driver to VRAM MM

The data structure |struct drm_vram_mm| and its helpers replace mgag200's
TTM-based memory manager. It's the same implementation; except for the type
names.

v4:
* don't select DRM_TTM or DRM_VRAM_MM_HELPER
v3:
* use drm_gem_vram_mm_funcs
* convert driver to drm_device-based instance
v2:
* implement mgag200_mmap() with drm_vram_mm_mmap()

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190508082630.15116-16-tzimmermann@suse.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

drm/mgag200: Convert mgag200 driver to |struct drm_gem_vram_object|

The data structure |struct drm_gem_vram_object| and its helpers replace
|struct mgag200_bo|. It's the same implementation; except for the type
names.

v4:
* cleanups from checkpatch.pl
* select config option DRM_VRAM_HELPER

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190508082630.15116-15-tzimmermann@suse.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

drm: fix compilations issues introduced by "drm: allow to use mmuless SoC"

Removing MMU configuration flag from DRM make few automatic
build failed when they answer yes to all flags.

Add asm/vga.h file on Blackfin architecture to not broke compilation.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Fixes: 62a0d98a188c ("drm: allow to use mmuless SoC")
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483789151-6603-1-git-send-email-benjamin.gaignard@linaro.org

drm/mgag200: make fbdev support really optional

Currently enabling MGA G200 DRM support automatically pulls in
fbdev dependency. However this dep is unnecessary since
DRM core already handles this for us (DRM_FBDEV_EMULATION).

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468586897-32298-5-git-send-email-tjakobi@math.uni-bielefeld.de

drm: Add separate Kconfig option for fbdev helpers

For drivers which might want to disable fbdev legacy support.

Select the new option in all drivers for now, so this shouldn't result
in any change. Drivers need some work anyway to make fbdev support
optional (if they have it implemented, that is), so the recommended
way to expose this is by adding per-driver options. At least as long
as most drivers don't support disabling the fbdev support.

v2: Update for new drm drivers msm and rcar-du. Note that Rob's msm
driver can already take advantage of this, which allows us to build
msm without any fbdev depencies in the kernel!

v3: Move the MODULE_* stuff from the fbdev helper file to
drm_crtc_helper.c.

Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Acked-by: Dave Airlie <airlied@linux.ie>
Reviewed-by: Chon Ming Lee <chon.ming.lee@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/mgag200: remove depends on CONFIG_EXPERIMENTAL

The CONFIG_EXPERIMENTAL config item has not carried much meaning for a
while now and is almost always enabled by default. As agreed during the
Linux kernel summit, remove it from any "depends on" lines in Kconfigs.

CC: Dave Airlie <airlied@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drm/kms: fix Kconfig for new drivers.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

mgag200: initial g200se driver (v2)

This is a driver for the G200 server engines chips,
it doesn't driver any of the Matrix G series desktop cards.

It will bind to G200 SE A,B, G200EV, G200WB, G200EH and G200ER cards.

Its based on previous work done my Matthew Garrett but remodelled
to follow the same style and flow as the AST server driver. It also
works along the same lines as the AST server driver wrt memory management.

There is no userspace driver planned, xf86-video-modesetting should be used.
It also appears these GPUs have no ARGB hw cursors.

v2: add missing tagfifo reset + G200 SE memory bw setup pieces.

Signed-off-by: Dave Airlie <airlied@redhat.com>