linux-kernel - Re: [PATCH v2 0/5] drm/bridge: samsung-dsim: fix various modes with ADV7535 bridge

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Message-ID: <1a25e5b9-43f6-47a4-877a-a0744dc6f56c@samsung.com>
Date:   Fri, 6 Oct 2023 18:16:51 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Michael Tretter <m.tretter@...gutronix.de>,
        Inki Dae <inki.dae@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de, Marco Felsch <m.felsch@...gutronix.de>,
        Adam Ford <aford173@...il.com>,
        Frieder Schrempf <frieder.schrempf@...tron.de>
Subject: Re: [PATCH v2 0/5] drm/bridge: samsung-dsim: fix various modes with
 ADV7535 bridge

On 06.10.2023 17:07, Michael Tretter wrote:
> I tested the i.MX8M Nano EVK with the NXP supplied MIPI-DSI adapter,
> which uses an ADV7535 MIPI-DSI to HDMI converter. I found that a few
> modes were working, but in many modes my monitor stayed dark.
>
> This series fixes the Samsung DSIM bridge driver to bring up a few more
> modes:
>
> The driver read the rate of the PLL ref clock only during probe.
> However, if the clock is re-parented to the VIDEO_PLL, changes to the
> pixel clock have an effect on the PLL ref clock. Therefore, the driver
> must read and potentially update the PLL ref clock on every modeset.
>
> I also found that the rounding mode of the porches and active area has
> an effect on the working modes. If the driver rounds up instead of
> rounding down and be calculates them in Hz instead of kHz, more modes
> start to work.
>
> The following table shows the modes that were working in my test without
> this patch set and the modes that are working now:
>
> |            Mode | Before | Now |
> | 1920x1080-60.00 | X      | X   |
> | 1920x1080-59.94 |        | X   |
> | 1920x1080-50.00 |        | X   |
> | 1920x1080-30.00 |        | X   |
> | 1920x1080-29.97 |        | X   |
> | 1920x1080-25.00 |        | X   |
> | 1920x1080-24.00 |        |     |
> | 1920x1080-23.98 |        |     |
> | 1680x1050-59.88 |        | X   |
> | 1280x1024-75.03 | X      | X   |
> | 1280x1024-60.02 | X      | X   |
> |  1200x960-59.99 |        | X   |
> |  1152x864-75.00 | X      | X   |
> |  1280x720-60.00 |        |     |
> |  1280x720-59.94 |        |     |
> |  1280x720-50.00 |        | X   |
> |  1024x768-75.03 |        | X   |
> |  1024x768-60.00 |        | X   |
> |   800x600-75.00 | X      | X   |
> |   800x600-60.32 | X      | X   |
> |   720x576-50.00 | X      | X   |
> |   720x480-60.00 |        |     |
> |   720x480-59.94 | X      |     |
> |   640x480-75.00 | X      | X   |
> |   640x480-60.00 |        | X   |
> |   640x480-59.94 |        | X   |
> |   720x400-70.08 |        |     |
>
> Interestingly, the 720x480-59.94 mode stopped working. However, I am
> able to bring up the 720x480 modes by manually hacking the active area
> (hsa) to 40 and carefully adjusting the clocks, but something still
> seems to be off.
>
> Unfortunately, a few more modes are still not working at all. The NXP
> downstream kernel has some quirks to handle some of the modes especially
> wrt. to the porches, but I cannot figure out, what the driver should
> actually do in these cases. Maybe there is still an error in the
> calculation of the porches and someone at NXP can chime in.
>
> Michael
>
> Signed-off-by: Michael Tretter <m.tretter@...gutronix.de>

All my Exynos-based test boards with DSI display panels still work fine 
with this patchset.

Feel free to add:

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>


> ---
> Changes in v2:
> - Specify limits for the PLL input clock in samsung_dsim_driver_data
> - Rephrase/clarify commit messages
> - Link to v1: https://lore.kernel.org/r/20230818-samsung-dsim-v1-0-b39716db6b7a@pengutronix.de
>
> ---
> Marco Felsch (1):
>        drm/bridge: samsung-dsim: add more mipi-dsi device debug information
>
> Michael Tretter (4):
>        drm/bridge: samsung-dsim: reread ref clock before configuring PLL
>        drm/bridge: samsung-dsim: update PLL reference clock
>        drm/bridge: samsung-dsim: adjust porches by rounding up
>        drm/bridge: samsung-dsim: calculate porches in Hz
>
>   drivers/gpu/drm/bridge/samsung-dsim.c | 54 +++++++++++++++++++++++++++--------
>   include/drm/bridge/samsung-dsim.h     |  3 ++
>   2 files changed, 45 insertions(+), 12 deletions(-)
> ---
> base-commit: b78b18fb8ee19f7a05f20c3abc865b3bfe182884
> change-id: 20230818-samsung-dsim-42346444bce5
>
> Best regards,

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland