Message-ID: <657416e8-bb05-42ca-b139-dc25177f5eb8@linux.dev>
Date: Tue, 11 Mar 2025 09:16:46 +0530
From: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Devarsh Thakkar <devarsht@...com>, Praneeth Bajjuri <praneeth@...com>,
 Udit Kumar <u-kumar1@...com>, Jayesh Choudhary <j-choudhary@...com>,
 DRI Development List <dri-devel@...ts.freedesktop.org>,
 Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 00/13] drm/bridge: cdns-dsi: Fix the color-shift issue

Hi,

All the patches within this series have been reviewed.
Are there any more concerns that should be taken care of?


On 26/02/25 21:22, Aradhya Bhatia wrote:
> Hello all,
> 
> This series provides some crucial fixes and improvements for the Cadence's DSI
> TX (cdns-dsi) controller found commonly in Texas Instruments' J7 family of SoCs,
> as well as in Sitara AM62P and AM62L SoCs.
> 
> Along with that, this series aims to fix the color-shift issue that has been
> going on with the DSI controller. This controller requires to be enabled before
> the previous entity enables its stream[0]. It's a strict requirement which, if
> not followed, causes the colors to "shift" on the display. The fix happens in
> 2 steps.
> 
>     1. The bridge pre_enable calls have been shifted before the crtc_enable and
>        the bridge post_disable calls have been shifted after the crtc_disable.
>        This has been done as per the definition of bridge pre_enable.
> 
>        "The display pipe (i.e. clocks and timing signals) feeding this bridge
>        will not yet be running when this callback is called".
> 
>        Since CRTC is also a source feeding the bridge, it should not be enabled
>        before the bridges in the pipeline are pre_enabled.
> 
>        The sequence of enable after this patch will look like:
> 
> 	        bridge[n]_pre_enable
> 	        ...
> 	        bridge[1]_pre_enable
> 
> 	        crtc_enable
> 	        encoder_enable
> 
> 	        bridge[1]_enable
> 	        ...
> 	        bridge[n]_enable
> 
>        and vice-versa for the bridge chain disable sequence.
> 
> 
>     2. The cdns-dsi enable / disable sequences have now been moved to pre_enable
>        and post_disable sequences. This is the only way to have cdns-dsi drivers
>        be up and ready before the previous entity is enables its streaming.
> 
> The DSI also spec requires the Clock and Data Lanes be ready before the DSI TX
> enables its stream[0]. A patch has been added to make the code wait for that to
> happen. Going ahead with further DSI (and DSS configuration), while the lanes
> are not ready, has been found to be another reason for shift in colors.
> 
> These patches have been tested with J721E based BeagleboneAI64 along with a
> RaspberryPi 7" DSI panel. The extra patches can be found in the
> "next_dsi-v10_1-tests" branch[1] of my github fork if anyone would like to test
> them.
> 
> Thanks,
> Aradhya
> 
> 
> * Important note about the authorship of patches *
> 
> All but one of the patches have been authored when I owned a "ti.com" based
> email id, i.e. <a-bhatia1@...com>. This email id is not in use anymore, and all
> the work done later has been part of my personal work. Since the original
> patches were authored using TI's email id, I have maintained the original
> authorships as they are, as well as their sign offs.
> 
> I have further added another sign off that uses my current (and personal) email
> id, the one that is being used to send this revision, i.e.
> <aradhya.bhatia@...ux.dev>.
> 
> 
> * Note on checkpatch warning in patch 11/13 *
> Patch 11/13 causes the checkpatch to flare up for 1 checkpatch 'check' -
> 
> CHECK: Lines should not end with a '('
> #77: FILE: drivers/gpu/drm/drm_atomic_helper.c:1304:
> +                       new_crtc_state = drm_atomic_get_new_crtc_state(
> 
> This patch is largely duplicating the original code, with minor differences to
> perform different operations. This line of code pre-exists in the file and
> have simply been duplicated. I have decided to keep it as is to maintain the
> uniformity and the originally intended readability. Should perhaps a fix be
> required, this patch/series is not the right place, and another patch can be
> created to fix this across the whole file.
> 
> 
> [0]: Section 12.6.5.7.3: "Start-up Procedure" [For DSI TX controller]
>      in TDA4VM Technical Reference Manual https://www.ti.com/lit/zip/spruil1
> 
> [1]: https://github.com/aradhya07/linux-ab/tree/next_dsi-v10_1-tests
> 
> 
> Change Log:
>   - Changes in v10:
>     - Rebase on latest linux-next (next-20250226).
>     - As part of rebase, update the patches to accommodate a couple of
>       widespread changes in DRM Framework -
>         - All the ("drm/atomic-helper: Change parameter name of ***") commits.
>         - All the ("drm/bridge: Pass full state to ***") commits.
>       (These updates are only trivial substitutions.)
>     - Add Tomi Valkeinen's T-b tags in all the patches.
> 
>   - Changes in v9:
>     - Fix the oops in 11/13 - where the encoder_bridge_enable _was_ pre_enabling
>       the bridges instead of enabling.
>     - Add the following tags:
>       - Dmitry Baryshkov's R-b in patches 2, 10, 11, and A-b in patch 12.
>       - Jayesh Choudhary's R-b in patch 12.
>       - Tomi Valkeinen's R-b in patches 2, 10, 11, 12.
> 
>   - Changes in v8:
>     - Move the phy de-initialization to bridge post_disable() instead of bridge
>       disable() in patch-3.
>     - Copy the private bridge state (dsi_cfg), in addition to the bridge_state,
>       in patch-9.
>     - Split patch v7:11/12 into three patches, v8:{10,11,12}/13, to separate out
>       different refactorings into different patches, and improve bisectability.
>     - Move patch v7:02/12 down to v8:06/12, to keep the initial patches for
>       fixes only.
>     - Drop patch v7:04/12 as it doesn't become relevant until patch v7:12/12.
>     - Add R-b tags of Dmitry Baryshkov in patch-9 and patch-3, and of
>       Tomi Valkeinen in patch-9.
>    
>   - Changes in v7:
>     - phy_init()/exit() were called from the PM path in v6. Change it back to
>       the bridge enable/disable path in patch-3, so that the phy_init() can go
>       back to being called after D-Phy reset assert.
>     - Reword commit text in patch-5 to explain the need of the fix.
>     - Drop the stray code in patch-10.
>     - Add R-b tag of Dmitry Baryshkov in patch-6.
> 
>   - Changes in v6:
>     - Reword patch 3 to better explain the fixes around phy de-init.
>     - Fix the Lane ready timeout condition in patch 7.
>     - Fix the dsi _bridge_atomic_check() implementation by adding a new
>       bridge state structure in patch 10.
>     - Rework and combine patches v5:11/13 and v5:12/13 to v6:11/12.
>     - Generate the patches of these series using the "patience" algorithm.
>       Note: All patches, except v6:11/12, *do not* differ from their default
>       (greedy) algorithm variants.
>       For patch 11, the patience algorithm significantly improves the readability.
>     - Rename and move the Bridge enable/disable enums from public to private
>       in patch 11.
>     - Add R-b tags of Tomi Valkeinen in patch 6, and Dmitry Baryshkov in patch 2.
> 
>   - Changes in v5:
>     - Fix subject and description in patch 1/13.
>     - Add patch to check the return value of
>       phy_mipi_dphy_get_default_config() (patch: 6/13).
>     - Change the Clk and Data Lane ready timeout from forever to 5s.
>     - Print an error instead of calling WARN_ON_ONCE in patch 7/13.
>     - Drop patch v4-07/11: "drm/bridge: cdns-dsi: Reset the DCS write FIFO".
>       There has been some inconsistencies found with this patch upon further
>       testing. This patch was being used to enable a DSI panel based on ILITEK
>       ILI9881C bridge. This will be debugged separately.
>     - Add patch to move the DSI mode check from _atomic_enable() to
>       _atomic_check() (patch: 10/13).
>     - Split patch v4-10/11 into 2 patches - 11/13 and 12/13.
>       Patch 11/13 separates out the Encoder-Bridge operations into a helper
>       function *without* changing the logic. Patch 12/13 then changes the order
>       of the encoder-bridge operations as was intended in the original patch.
>     - Add detailed comment for patch 13/13.
>     - Add Tomi Valkeinen's R-b in patches 1, 2, 4, 5, 7, 8, 9, 13.
> 
>   - Changes in v4:
>     - Add new patch, "drm/bridge: cdns-dsi: Move to devm_drm_of_get_bridge()",
>       to update to an auto-managed way of finding next bridge in the chain.
>     - Drop patch "drm/bridge: cdns-dsi: Fix the phy_initialized variable" and
>       add "drm/bridge: cdns-dsi: Fix Phy _init() and _exit()" that properly
>       de-initializes the Phy and maintains the initialization state.
>     - Reword patch "drm/bridge: cdns-dsi: Reset the DCS write FIFO" to explain
>       the HW concerns better.
>     - Add R-b tag from Dmitry Baryshkov for patches 1/11 and 8/11.
> 
>   - Changes in v3:
>     - Reword the commit message for patch "drm/bridge: cdns-dsi: Fix OF node
>       pointer".
>     - Add a new helper API to figure out DSI host input pixel format
>       in patch "drm/mipi-dsi: Add helper to find input format".
>     - Use a common function for bridge pre-enable and enable, and bridge disable
>       and post-disable, to avoid code duplication.
>     - Add T-b tag from Dominik Haller in patch 5/10. (Missed to add it in v2).
>     - Add R-b tag from Dmitry Baryshkov for patch 8/10.
> 
>   - Changes in v2:
>     - Drop patch "drm/tidss: Add CRTC mode_fixup"
>     - Split patch "drm/bridge: cdns-dsi: Fix minor bugs" into 4 separate ones
>     - Drop support for early_enable/late_disable APIs and instead re-order the
>       pre_enable / post_disable APIs to be called before / after crtc_enable /
>       crtc_disable.
>     - Drop support for early_enable/late_disable in cdns-dsi and use
>       pre_enable/post_disable APIs instead to do bridge enable/disable.
> 
> 
> Previous versions:
> 
> v1: https://lore.kernel.org/all/20240511153051.1355825-1-a-bhatia1@ti.com/
> v2: https://lore.kernel.org/all/20240530093621.1925863-1-a-bhatia1@ti.com/
> v3: https://lore.kernel.org/all/20240617105311.1587489-1-a-bhatia1@ti.com/
> v4: https://lore.kernel.org/all/20240622110929.3115714-1-a-bhatia1@ti.com/
> v5: https://lore.kernel.org/all/20241019195411.266860-1-aradhya.bhatia@linux.dev/
> v6: https://lore.kernel.org/all/20250111192738.308889-1-aradhya.bhatia@linux.dev/
> v7: https://lore.kernel.org/all/20250114055626.18816-1-aradhya.bhatia@linux.dev/
> v8: https://lore.kernel.org/all/20250126191551.741957-1-aradhya.bhatia@linux.dev/
> v9: https://lore.kernel.org/all/20250209121032.32655-1-aradhya.bhatia@linux.dev/
> 
> Aradhya Bhatia (13):
>   drm/bridge: cdns-dsi: Fix connecting to next bridge
>   drm/bridge: cdns-dsi: Fix phy de-init and flag it so
>   drm/bridge: cdns-dsi: Fix the clock variable for mode_valid()
>   drm/bridge: cdns-dsi: Check return value when getting default PHY
>     config
>   drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready
>   drm/bridge: cdns-dsi: Move to devm_drm_of_get_bridge()
>   drm/mipi-dsi: Add helper to find input format
>   drm/bridge: cdns-dsi: Support atomic bridge APIs
>   drm/bridge: cdns-dsi: Move DSI mode check to _atomic_check()
>   drm/atomic-helper: Refactor crtc & encoder-bridge op loops into
>     separate functions
>   drm/atomic-helper: Separate out bridge pre_enable/post_disable from
>     enable/disable
>   drm/atomic-helper: Re-order bridge chain pre-enable and post-disable
>   drm/bridge: cdns-dsi: Use pre_enable/post_disable to enable/disable
> 
>  .../gpu/drm/bridge/cadence/cdns-dsi-core.c    | 224 ++++++++++++++----
>  .../gpu/drm/bridge/cadence/cdns-dsi-core.h    |   2 -
>  drivers/gpu/drm/drm_atomic_helper.c           | 160 +++++++++++--
>  drivers/gpu/drm/drm_mipi_dsi.c                |  37 +++
>  include/drm/drm_mipi_dsi.h                    |   1 +
>  5 files changed, 348 insertions(+), 76 deletions(-)
> 
> 
> base-commit: 8433c776e1eb1371f5cd40b5fd3a61f9c7b7f3ad

-- 
Regards
Aradhya

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