Re: [PATCH v1 4/6] drm: panel-simple: add Hitachi 3.5" QVGA panel

From: Sam Ravnborg <sam@ravnborg.org>
To: Doug Anderson <dianders@chromium.org>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>, "Søren Andersen" <san@skov.dk>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	"Sebastian Reichel" <sebastian.reichel@collabora.com>
Subject: Re: [PATCH v1 4/6] drm: panel-simple: add Hitachi 3.5" QVGA panel
Date: Fri, 5 Jun 2020 19:19:19 +0200	[thread overview]
Message-ID: <20200605171919.GD207594@ravnborg.org> (raw)
In-Reply-To: <CAD=FV=WyErT-M=g74vyFjYHNQw9xj7ny_czHhjtUQbTDJUAjag@mail.gmail.com>

Hi Doug.

On Mon, Jun 01, 2020 at 05:30:53PM -0700, Doug Anderson wrote:
> Hi,
> 
> On Mon, Jun 1, 2020 at 1:33 AM Sam Ravnborg <sam@ravnborg.org> wrote:
> >
> > This panel is used on evaluation boards for Atmel at91sam9261 and
> > at91sam6263.
> >
> > Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Thierry Reding <thierry.reding@gmail.com>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > ---
> >  drivers/gpu/drm/panel/panel-simple.c | 29 ++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> > index 8624bb80108c..25c96639631f 100644
> > --- a/drivers/gpu/drm/panel/panel-simple.c
> > +++ b/drivers/gpu/drm/panel/panel-simple.c
> > @@ -1813,6 +1813,32 @@ static const struct panel_desc hannstar_hsd100pxn1 = {
> >         .connector_type = DRM_MODE_CONNECTOR_LVDS,
> >  };
> >
> > +static const struct drm_display_mode hitachi_tx09d71vm1cca_mode = {
> > +       .clock = 4965000,
> 
> This is the pixel clock in kHz, right?  So it runs at almost 5 Terahertz?
> 
> 
> > +       .hdisplay = 240,
> > +       .hsync_start = 240 + 0,
> > +       .hsync_end = 240 + 0 + 5,
> > +       .htotal = 240 + 0 + 5 + 1,
> > +       .vdisplay = 320,
> > +       .vsync_start = 320 + 0,
> > +       .vsync_end = 320 + 0 + 1,
> > +       .vtotal = 320 + 0 + 1 + 1,
> 
> Some random datasheet I found has really different numbers.  If the
> numbers above are what everyone is using then I suppose it's fine,
> just curious why the mismatch.

The timing comes from:
arch/arm/boot/dts/at91sam9263ek.dts - that include display timings for
the panel on the evaluation board.
I did not verify any datasheet - I just blindly copied what was there.
And clock was obviously not properly adjusted to khz.

Will fix in v2 - will also try to find a datasheet this time.

Thanks for noticing!

	Sam