Re: [PATCH 27/33] drm/panel-simple: Fix dotclock for Sharp LQ035Q7DB03

Vladimir Zapolskiy
2020-03-02T21:50:22Z

Hi Ville,

On 3/2/20 10:34 PM, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The currently listed dotclock disagrees with the currently
> listed vrefresh rate. Change the dotclock to match the vrefresh.
>
> Someone tell me which (if either) of the dotclock or vreresh is
> correct?

yes, I will tell you, see my answer below.

Adding Linus as a person who may be interested in PL111 specifics.

> Cc: Vladimir Zapolskiy <vz@mleia.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/panel/panel-simple.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index 3012b47c1e4e..7526af2d6d95 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -2949,7 +2949,7 @@ static const struct panel_desc sharp_lq070y3dg3b = {
> };
>
> static const struct drm_display_mode sharp_lq035q7db03_mode = {
> - .clock = 5500,
> + .clock = 5419,
> .hdisplay = 240,
> .hsync_start = 240 + 16,
> .hsync_end = 240 + 16 + 7,
>

Here .clock is correct, you may find the usage of the panel in
lpc3250-phy3250.dts example, and the PL111 controller on the SoC
won't be able to provide the exactly computed `.clock = 5419'.

So, I have to NAK this change, in this example the difference
between the declared and the computed .vreresh is one Hz, which
I hope can be accepted as negligible and ignorable, otherwise,
if you insist, please correct the .vrefresh from 60 to 61.

--
Best wishes,
Vladimir