[PATCH 3/3] drm/mipi: use dcs write for mipi_dsi_dcs_set_tear_scanline

[Emil Velikov]

On Thu, 7 May 2020 at 13:29, Vinay Simha B N <simhavcs at gmail.com> wrote:
>
> Emil,
>
> Reply inline
>
> On Tue, 5 May 2020 at 9:35 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>
>> From: Emil Velikov <emil.velikov at collabora.com>
>>
>> The helper uses the MIPI_DCS_SET_TEAR_SCANLINE, although it's currently
>> using the generic write. This does not look right.
>>
>> Perhaps some platforms don't distinguish between the two writers?
>>
>> Cc: Robert Chiras <robert.chiras at nxp.com>
>> Cc: Vinay Simha BN <simhavcs at gmail.com>
>> Cc: Jani Nikula <jani.nikula at intel.com>
>> Cc: Thierry Reding <treding at nvidia.com>
>> Fixes: e83950816367 ("drm/dsi: Implement set tear scanline")
>> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
>> ---
>> Robert, can you please test this against the only user - the Raydium
>> RM67191 panel driver that you introduced.
>>
>> Thanks
>>
>> Vinay, can you confirm if this is a genuine typo or there's something
>> really subtle happening.
>
> this has been tested on nexus 7 with jdi panel.
The jdi panel (JDI LT070ME05000 I believe) does not use the function, hmm.

Looking through the ML archive - the call in the first 4 revisions of the patch.
Then with v5 it has magically disappeared alongside mipi_dsi_dcs_set_tear_on().

No comment explaining why though - does the driver work w/o both of those?

> I did not understand what is the typo here?
> We need to use DC’s write instead of generic write?

I believe the clue is in the command name - MIPI_DSI_DCS. I was going
to double-check with the spec although it's members only :-\
Based on the usage in DRM, all DCS commands are issued via
mipi_dsi_dcs_{read,write}

Thanks
Emil