drm/vkms: move wb's atomic_check from encoder to connector

As the renamed drm_atomic_helper_check_wb_connector_state() now accepts
drm_writeback_connector as the first argument (instead of drm_encoder),
move the VKMS writeback atomic_check from drm_encoder_helper_funcs to
drm_connector_helper_funcs. Also drop the vkms_wb_encoder_helper_funcs,
which have become empty now.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231208010314.3395904-3-dmitry.baryshkov@linaro.org

drm/atomic-helper: rename drm_atomic_helper_check_wb_encoder_state

The drm_atomic_helper_check_wb_encoder_state() function doesn't use
encoder for anything other than getting the drm_device instance. The
function's description talks about checking the writeback connector
state, not the encoder state. Moreover, there is no such thing as an
encoder state, encoders generally do not have a state on their own.

Rename the function to drm_atomic_helper_check_wb_connector_state()
and change arguments to drm_writeback_connector and drm_atomic_state.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231208010314.3395904-2-dmitry.baryshkov@linaro.org

drm/vkms: Isolate writeback pixel conversion functions

All convertions from the ARGB16161616 format follow the same structure.
Instead of repeting the same structure for each supported format, create
a function to encapsulate the common logic and isolate the pixel
conversion functions in a callback function.

Suggested-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515135204.115393-4-mcanal@igalia.com

drm/vkms: Enable ARGB8888 support for writeback

The VKMS already has a function to convert ARGB16161616 to ARGB8888, so
it is possible to use this function to provide the writeback support for
the ARGB8888 format. Therefore, add the ARGB8888 format to the writeback
format list.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515135204.115393-3-mcanal@igalia.com

drm/vkms: Reduce critical section

The spinlock composer_lock protects the variables crc_pending,
wb_pending, frame_start and frame_end, which are variables that are used
by the composer worker. There is no need to protect the wb_frame_info
information with a spinlock. Therefore, reduce the critical section of
the lock by removing the assignments to the wb_frame_info from the
critical section.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Arthur Grillo <arthurgrillo@riseup.net>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515135204.115393-2-mcanal@igalia.com

drm: vkms: Add support to the RGB565 format

This commit also adds new helper macros to deal with fixed-point
arithmetic.

It was done to improve the precision of the conversion to ARGB16161616
since the "conversion ratio" is not an integer.

V3: Adapt the handlers to the new format introduced in patch 7 V3.
V5: Minor improvements
V6: Minor improvements (Pekka Paalanen)

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-10-igormtorrente@gmail.com

drm: vkms: Adds XRGB_16161616 and ARGB_1616161616 formats

This will be useful to write tests that depends on these formats.

ARGB and XRGB follows the a similar implementation of the former formats.
Just adjusting for 16 bits per channel.

V3: Adapt the handlers to the new format introduced in patch 7 V3.
V5: Minor improvements
Added le16_to_cpu/cpu_to_le16 to the 16 bits color read/writes.

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-9-igormtorrente@gmail.com

drm: vkms: Supports to the case where primary plane doesn't match the CRTC

We will remove the current assumption that the primary plane has the
same size and position as CRTC and that the primary plane is the
bottom-most in zpos order, or is even enabled. At least as far
as the blending machinery is concerned.

For that we will add CRTC dimension information to `vkms_crtc_state`
and add a opaque black backgound color.

Because now we need to fill the background, we had a loss in
performance with this change. Results running the IGT[1] test
`igt@kms_cursor_crc@pipe-a-cursor-512x512-onscreen` ten times:

| Frametime |
|:--------------------------------------------:|
| Implementation | Previous | This commit |
|:---------------:|:---------:|:--------------:|
| frametime range | 5~18 ms | 10~22 ms |
| Average | 8.47 ms | 12.32 ms |

[1] IGT commit id: bc3f6833a12221a46659535dac06ebb312490eb4

V6: Improve the commit description (Pekka Paalanen).
Update some comments (Pekka Paalanen).
Remove some fields from `vkms_crtc_state` and move where
some variables are set (Pekka Paalanen).

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-8-igormtorrente@gmail.com

drm: vkms: Refactor the plane composer to accept new formats

Currently the blend function only accepts XRGB_8888 and ARGB_8888
as a color input.

This patch refactors all the functions related to the plane composition
to overcome this limitation.

The pixels blend is done using the new internal format. And new handlers
are being added to convert a specific format to/from this internal format.

So the blend operation depends on these handlers to convert to this common
format. The blended result, if necessary, is converted to the writeback
buffer format.

This patch introduces three major differences to the blend function.
1 - All the planes are blended at once.
2 - The blend calculus is done as per line instead of per pixel.
3 - It is responsible to calculates the CRC and writing the writeback
buffer(if necessary).

These changes allow us to allocate way less memory in the intermediate
buffer to compute these operations. Because now we don't need to
have the entire intermediate image lines at once, just one line is
enough.

| Memory consumption (output dimensions) |
|:--------------------------------------:|
| Current | This patch |
|:------------------:|:-----------------:|
| Width * Heigth | 2 * Width |

Beyond memory, we also have a minor performance benefit from all
these changes. Results running the IGT[1] test
`igt@kms_cursor_crc@pipe-a-cursor-512x512-onscreen` ten times:

| Frametime |
|:------------------------------------------:|
| Implementation | Current | This commit |
|:---------------:|:---------:|:------------:|
| frametime range | 9~22 ms | 5~17 ms |
| Average | 11.4 ms | 7.8 ms |

[1] IGT commit id: bc3f6833a12221a46659535dac06ebb312490eb4

V2: Improves the performance drastically, by performing the operations
per-line and not per-pixel(Pekka Paalanen).
Minor improvements(Pekka Paalanen).
V3: Changes the code to blend the planes all at once. This improves
performance, memory consumption, and removes much of the weirdness
of the V2(Pekka Paalanen and me).
Minor improvements(Pekka Paalanen and me).
V4: Rebase the code and adapt it to the new NUM_OVERLAY_PLANES constant.
V5: Minor checkpatch fixes and the removal of TO-DO item(Melissa Wen).
Several security/robustness improvents(Pekka Paalanen).
Removes check_planes_x_bounds function and allows partial
partly off-screen(Pekka Paalanen).
V6: Fix a mismatch of some variable sizes (Pekka Paalanen).
Several minor improvements (Pekka Paalanen).

Reviewed-by: Melissa Wen <mwen@igalia.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-7-igormtorrente@gmail.com

drm: vkms: Add fb information to `vkms_writeback_job`

This commit is the groundwork to introduce new formats to the planes and
writeback buffer. As part of it, a new buffer metadata field is added to
`vkms_writeback_job`, this metadata is represented by the `vkms_frame_info`
struct.

Also adds two new function pointers (`line_to_frame_func` and
`frame_to_line_func`) are defined to handle format conversion
from/to internal format.

A new internal format(`struct pixel_argb_u16`) is introduced to deal with
all possible inputs. It consists of 16 bits fields that represent each of
the channels.

These things will allow us, in the future, to have different compositing
and wb format types.

V2: Change the code to get the drm_framebuffer reference and not copy its
contents (Thomas Zimmermann).
V3: Drop the refcount in the wb code (Thomas Zimmermann).
V5: Add {wb,plane}_format_transform_func to vkms_writeback_job
and vkms_plane_state (Pekka Paalanen)
V6: Improvements to some struct/struct members names (Pekka Paalanen).
Splits this patch in two (Pekka Paalanen).
V7: Replace line_to_frame_func and frame_to_line_func typedefs
with the function signature and void* (Melissa Wen).

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-6-igormtorrente@gmail.com

drm: drm_atomic_helper: Add a new helper to deal with the writeback connector validation

Add a helper function to validate the connector configuration received in
the encoder atomic_check by the drivers.

So the drivers don't need to do these common validations themselves.

V2: Move the format verification to a new helper at the drm_atomic_helper.c
(Thomas Zimmermann).
V3: Format check improvements (Leandro Ribeiro).
Minor improvements(Thomas Zimmermann).
V5: Fix some grammar issues in the commit message (André Almeida).

Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-4-igormtorrente@gmail.com

drm: Drop drm_edid.h from drm_crtc.h

drm_crtc.h has no need for drm_edid.h, so don't include it.
Avoids useless rebuilds of the entire universe when
touching drm_edid.h.

Quite a few placs do currently depend on drm_edid.h without
actually including it directly. All of those need to be fixed
up.

v2: Fix up i915 and msm some more
v3: Fix alphabetical ordering (Sam)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614090245.30283-1-ville.syrjala@linux.intel.com
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>

drm: allow passing possible_crtcs to drm_writeback_connector_init()

Clients of drm_writeback_connector_init() initialize the
possible_crtcs and then invoke the call to this API.

To simplify things, allow passing possible_crtcs as a parameter
to drm_writeback_connector_init() and make changes to the
other drm drivers to make them compatible with this change.

changes in v2:
- split the changes according to their functionality

changes in v3:
- allow passing possible_crtcs for existing users of
drm_writeback_connector_init()
- squash the vendor changes into the same commit so
that each patch in the series can compile individually

changes in v4:
- keep only changes related to possible_crtcs
- add line breaks after ARRAY_SIZE
- stop using temporary variables for possible_crtcs

changes in v5:
- None

changes in v6:
- None

changes in v7:
- wrap long lines to match the coding style of existing drivers
- Fix indentation and remove parenthesis where not needed
- use u32 instead of uint32_t for possible_crtcs

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Patchwork: https://patchwork.freedesktop.org/patch/483501/
Link: https://lore.kernel.org/r/1650984096-9964-2-git-send-email-quic_abhinavk@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

dma-buf-map: Rename to iosys-map

Rename struct dma_buf_map to struct iosys_map and corresponding APIs.
Over time dma-buf-map grew up to more functionality than the one used by
dma-buf: in fact it's just a shim layer to abstract system memory, that
can be accessed via regular load and store, from IO memory that needs to
be acessed via arch helpers.

The idea is to extend this API so it can fulfill other needs, internal
to a single driver. Example: in the i915 driver it's desired to share
the implementation for integrated graphics, which uses mostly system
memory, with discrete graphics, which may need to access IO memory.

The conversion was mostly done with the following semantic patch:

@r1@
@@
- struct dma_buf_map
+ struct iosys_map

@r2@
@@
(
- DMA_BUF_MAP_INIT_VADDR
+ IOSYS_MAP_INIT_VADDR
|
- dma_buf_map_set_vaddr
+ iosys_map_set_vaddr
|
- dma_buf_map_set_vaddr_iomem
+ iosys_map_set_vaddr_iomem
|
- dma_buf_map_is_equal
+ iosys_map_is_equal
|
- dma_buf_map_is_null
+ iosys_map_is_null
|
- dma_buf_map_is_set
+ iosys_map_is_set
|
- dma_buf_map_clear
+ iosys_map_clear
|
- dma_buf_map_memcpy_to
+ iosys_map_memcpy_to
|
- dma_buf_map_incr
+ iosys_map_incr
)

@@
@@
- #include <linux/dma-buf-map.h>
+ #include <linux/iosys-map.h>

Then some files had their includes adjusted and some comments were
update to remove mentions to dma-buf-map.

Since this is not specific to dma-buf anymore, move the documentation to
the "Bus-Independent Device Accesses" section.

v2:
- Squash patches

v3:
- Fix wrong removal of dma-buf.h from MAINTAINERS
- Move documentation from dma-buf.rst to device-io.rst

v4:
- Change documentation title and level

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204170541.829227-1-lucas.demarchi@intel.com

drm/vkms: Use offset-adjusted shadow-plane mappings and output

For framebuffers with non-zero offset fields, shadow-plane helpers
provide a pointer to the first byte of the contained data. Use it in
vkms.

Also provide use the offset-adjusted data address for the writeback
job's output buffers. Output framebuffers with non-zero offsets now
have their content written to the correct location.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210803125928.27780-12-tzimmermann@suse.de

drm/gem: Provide offset-adjusted framebuffer BO mappings

Add an additional argument to drm_gem_fb_vmap() to return each BO's
mapping adjusted by the respective offset. Update all callers.

The newly returned values point to the first byite of the data stored
in the framebuffer BOs. Drivers that access the BO data should use it.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210803125928.27780-2-tzimmermann@suse.de

drm/vkms: Map output framebuffer BOs with drm_gem_fb_vmap()

Abstract the framebuffer details by mappings its BOs with a call
to drm_gem_fb_vmap(). Unmap with drm_gem_fb_vunamp().

Before, the output address with stored as raw pointer in the priv
field of struct drm_writeback_job. Introduce the new type
struct vkms_writeback_job, which holds the output mappings addresses
while the writeback job is active.

The patchset also cleans up some internal casting an setup of the
output addresses. No functional changes.

v3:
* free instances of struct vkms_writeback_job on cleanup
or errors

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210730183511.20080-6-tzimmermann@suse.de

drm: Switch to %p4cc format modifier

Switch DRM drivers from drm_get_format_name() to %p4cc. This gets rid of a
large number of temporary variables at the same time.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210216155723.17109-4-sakari.ailus@linux.intel.com

drm: Pass the full state to connectors atomic functions

The current atomic helpers have either their object state being passed as
an argument or the full atomic state.

The former is the pattern that was done at first, before switching to the
latter for new hooks or when it was needed.

Now that the CRTCs have been converted, let's move forward with the
connectors to provide a consistent interface.

The conversion was done using the coccinelle script below, and built tested
on all the drivers.

@@
identifier connector, connector_state;
@@

struct drm_connector_helper_funcs {
...
struct drm_encoder* (*atomic_best_encoder)(struct drm_connector *connector,
- struct drm_connector_state *connector_state);
+ struct drm_atomic_state *state);
...
}

@@
identifier connector, connector_state;
@@

struct drm_connector_helper_funcs {
...
void (*atomic_commit)(struct drm_connector *connector,
- struct drm_connector_state *connector_state);
+ struct drm_atomic_state *state);
...
}

@@
struct drm_connector_helper_funcs *FUNCS;
identifier state;
identifier connector, connector_state;
identifier f;
@@

f(..., struct drm_atomic_state *state, ...)
{
<+...
- FUNCS->atomic_commit(connector, connector_state);
+ FUNCS->atomic_commit(connector, state);
...+>
}

@@
struct drm_connector_helper_funcs *FUNCS;
identifier state;
identifier connector, connector_state;
identifier var, f;
@@

f(struct drm_atomic_state *state, ...)
{
<+...
- var = FUNCS->atomic_best_encoder(connector, connector_state);
+ var = FUNCS->atomic_best_encoder(connector, state);
...+>
}

@ connector_atomic_func @
identifier helpers;
identifier func;
@@

(
static struct drm_connector_helper_funcs helpers = {
...,
.atomic_best_encoder = func,
...,
};
|
static struct drm_connector_helper_funcs helpers = {
...,
.atomic_commit = func,
...,
};
)

@@
identifier connector_atomic_func.func;
identifier connector;
symbol state;
@@

func(struct drm_connector *connector,
- struct drm_connector_state *state
+ struct drm_connector_state *connector_state
)
{
...
- state
+ connector_state
...
}

@ ignores_state @
identifier connector_atomic_func.func;
identifier connector, connector_state;
@@

func(struct drm_connector *connector,
struct drm_connector_state *connector_state)
{
... when != connector_state
}

@ adds_state depends on connector_atomic_func && !ignores_state @
identifier connector_atomic_func.func;
identifier connector, connector_state;
@@

func(struct drm_connector *connector, struct drm_connector_state *connector_state)
{
+ struct drm_connector_state *connector_state = drm_atomic_get_new_connector_state(state, connector);
...
}

@ depends on connector_atomic_func @
identifier connector_atomic_func.func;
identifier connector_state;
identifier connector;
@@

func(struct drm_connector *connector,
- struct drm_connector_state *connector_state
+ struct drm_atomic_state *state
)
{ ... }

@ include depends on adds_state @
@@

#include <drm/drm_atomic.h>

@ no_include depends on !include && adds_state @
@@

+ #include <drm/drm_atomic.h>
#include <drm/...>

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201118094758.506730-1-maxime@cerno.tech

drm/gem: Use struct dma_buf_map in GEM vmap ops and convert GEM backends

This patch replaces the vmap/vunmap's use of raw pointers in GEM object
functions with instances of struct dma_buf_map. GEM backends are
converted as well. For most of them, this simply changes the returned type.

TTM-based drivers now return information about the location of the memory,
either system or I/O memory. GEM VRAM helpers and qxl now use ttm_bo_vmap()
et al. Amdgpu, nouveau and radeon use drm_gem_ttm_vmap() et al instead of
implementing their own vmap callbacks.

v7:
* init QXL cursor to mapped BO buffer (kernel test robot)
v5:
* update vkms after switch to shmem
v4:
* use ttm_bo_vmap(), drm_gem_ttm_vmap(), et al. (Daniel, Christian)
* fix a trailing { in drm_gem_vmap()
* remove several empty functions instead of converting them (Daniel)
* comment uses of raw pointers with a TODO (Daniel)
* TODO list: convert more helpers to use struct dma_buf_map

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Christian König <christian.koenig@amd.com>
Tested-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201103093015.1063-7-tzimmermann@suse.de

drm/vkms: Switch to shmem helpers

Inspired by a patch by Chris Wilson for vgem. Plus this gives us vmap
at the gem bo level, which we need for generic fbdev emulation.

Luckily shmem also tracks ->vaddr, so we just need to adjust the code
all over a bit to make this fit.

Also wire up handle_to_fd, dunno why that was missing.

v2:
- Drop now unused container_of #define (Melissa)
- Make sure we keep creating cached objects, this is for testing
(Thomas)

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201013111027.375999-1-daniel.vetter@ffwll.ch

drm/vkms: Add support for writeback

This patch implements the necessary functions to add writeback support
for vkms. This feature is useful for testing compositors if you don't
have hardware with writeback support.

Change in V4 (Emil and Melissa):
- Move signal completion above drm_crtc_add_crc_entry()
- Make writeback always available
- Use appropriate namespace
- Drop fb check in vkms_wb_atomic_commit
- Make vkms_set_composer visible for writeback code
- Enable composer operation on prepare_job and disable it on cleanup_job
- Drop extra space at the end of the file
- Rebase

Change in V3 (Daniel):
- If writeback is enabled, compose everything into the writeback buffer
instead of CRC private buffer
- Guarantees that the CRC will match exactly what we have in the
writeback buffer.

Change in V2:
- Rework signal completion (Brian)
- Integrates writeback with active_planes (Daniel)
- Compose cursor (Daniel)

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200830142000.146706-4-rodrigosiqueiramelo@gmail.com