Message-ID: <e894d5be-21ba-4028-816b-e47ce36e03d5@ideasonboard.com>
Date: Tue, 11 Feb 2025 11:09:15 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
 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 v9 00/13]drm/bridge: cdns-dsi: Fix the color-shift issue

Hi,

On 09/02/2025 14:10, 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.

I tested this on AI-64 with an RPi panel. The image is not quite stable, 
but that's always been the case with AI-64 and this panel, and I think 
it's not related to anything in this series (there's probably more to 
fix with the cdns-dsi...).

I think this series is ready for merging.

Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

  Tomi

> 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-v9_2-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 warnings in patch 11/13 *
> Patch 11/13 caueses the checkpatch to flare up for 1 warning, and 1 check -
> 
> WARNING: line length of 101 exceeds 100 columns
> #63: FILE: drivers/gpu/drm/drm_atomic_helper.c:1252:
> 
> CHECK: Lines should not end with a '('
> #77: FILE: drivers/gpu/drm/drm_atomic_helper.c:1266:
> 
> This patch is largely duplicating the original code, with minor differences to
> perform different operations. Both these lines of code pre-exist in the file and
> have simply been duplicated. I have decided to keep them as is to maintain the
> uniformity and the originaly 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-v9_2-tests
> 
> 
> Change Log:
>    - 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/
> 
> 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    | 225 ++++++++++++++----
>   .../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, 349 insertions(+), 76 deletions(-)
> 
> 
> base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04

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