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

[Vinay Simha B N]

hi emil,

On Wed, May 13, 2020 at 3:17 PM Emil Velikov <emil.l.velikov at gmail.com> wrote:
>
> Hi Vinay,
>
> On Thu, 7 May 2020 at 17:18, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> >
> > 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?
> >
> Any ideas, does the driver work in today's state?
Initially I had used cmd mode, later modified to video mode panel,
since to control the panel in cmd mode is not available for mdp4.
so mipi_dsi_dcs_set_tear_on was not used.


>
> > > 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}
> >
> Do you agree with the rationale? Alternatively, do you have a
> reference to the Android tree where the generic write is used.
>
default android nexus 7 kernel
https://github.com/vinaysimhabn/msm/commits/nexus7-msm-flo-3.4-lollipop-release
> Thanks
> Emil



--
regards,
vinaysimha