[PATCH] drm: bridge: adv7511: fix reading edid segments

[Frieder Schrempf]

On 26.10.23 13:30, Emil Abildgaard Svendsen wrote:
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> 
> Currently reading EDID only works because usually only two EDID blocks
> of 128 bytes is used. Where an EDID segment holds 256 bytes or two EDID
> blocks. And the first EDID segment read works fine but E-EDID specifies
> up to 128 segments.
> 
> The logic is broken so change EDID segment index to multiple of 256
> bytes and not 128 (block size).
> 
> Also change check of DDC status. Instead of silently not reading EDID
> when in "IDLE" state [1]. Check if the DDC controller is in reset
> instead (no HPD).
> 
> [1]
> ADV7511 Programming Guide: Table 11: DDCController Status:
> 
>   0xC8 [3:0]  DDC Controller State
> 
>   0000        In Reset (No Hot Plug Detected)
>   0001        Reading EDID
>   0010        IDLE (Waiting for HDCP Requested)
>   0011        Initializing HDCP
>   0100        HDCP Enabled
>   0101        Initializing HDCP Repeater
> 
> Signed-off-by: Emil Svendsen <emas at bang-olufsen.dk>

This patch somehow seems to break the reported display modes with my
setup (i.MX8MM DSI -> ADV7535 -> FullHD screen) when I test on current
linux-next.

Without this patch I get 30 valid modes reported by modetest.

With this patch applied I only get 5 valid modes. The screen still comes
up with the 1080p default mode though, that is now not even in the list
anymore.