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

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Message-ID: <a95481b7-e38c-4b7c-be49-4c74e07d3523@kontron.de>
Date:   Mon, 4 Sep 2023 16:02:29 +0200
From:   Frieder Schrempf <frieder.schrempf@...tron.de>
To:     Michael Tretter <m.tretter@...gutronix.de>,
        Inki Dae <inki.dae@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Marek Szyprowski <m.szyprowski@...sung.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:     kernel@...gutronix.de, Marco Felsch <m.felsch@...gutronix.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 0/5] drm/bridge: samsung-dsim: fix various modes with
 ADV7535 bridge

Hi Michael,

On 28.08.23 17:59, 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.

Thanks for working on this! We tested these patches with our Kontron BL
i.MX8MM board and a "10.1inch HDMI LCD (E)" display from Waveshare  [1].

Without this series we don't get an image with the default mode of the
display (1024x600). With this series applied, it's now working.

For the whole series:

Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de> # Kontron BL
i.MX8MM + Waveshare 10.1inch HDMI LCD (E)

Thanks
Frieder

[1] https://www.waveshare.com/10.1inch-hdmi-lcd-e.htm