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

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Vladimir Zapolskiy <vz@mleia.com>
Cc: Thierry Reding <treding@nvidia.com>, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 27/33] drm/panel-simple: Fix dotclock for Sharp LQ035Q7DB03
Date: Tue, 3 Mar 2020 16:49:55 +0200	[thread overview]
Message-ID: <20200303144955.GU13686@intel.com> (raw)
In-Reply-To: <dbdfa047-e8b5-ee08-2824-1069b8292d89@mleia.com>

On Mon, Mar 02, 2020 at 11:40:07PM +0200, Vladimir Zapolskiy wrote:
> 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'.

OK, I'll drop this one.

> 
> 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.

I'm going to nuke .vrefresh entirely.

-- 
Ville Syrjälä
Intel
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