Re: [PATCH v9 03/14] drm/mediatek: Add DSI sub driver

[CK Hu <ck.hu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

Hi Philipp:

On Wed, 2016-02-03 at 12:01 +0100, Philipp Zabel wrote:
> Hi Daniel,
> 

> > > +static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
> > > +{
> > > +       if (!dsi->enabled)
> > > +               return;
> > > +
> > > +       if (dsi->panel) {
> > > +               if (drm_panel_disable(dsi->panel)) {
> > > +                       DRM_ERROR("failed to disable the panel\n");
> > > +                       return;
> > > +               }
> > > +       }
> > > +
> > > +       mtk_dsi_poweroff(dsi);
> > 
> > The order is a bit suspicious here; I would expect to poweroff dsi
> > before the panel to mirror the turn on order.
> 
> CK, could you comment on this?
> 

According to the experience of other Mediatek SoC,
In mtk_output_dsi_enable(), we should do power on dsi first and then
prepare panel because dsi should be ready to receive panel prepare error
message. So we should disable panel and then power off dsi in
mtk_output_dsi_disable().

> I can reorder this, but I'm not sure about the reasoning (what happens
> hardware wise if we just cut panel power vs. if the DSI panel first sees
> the ULP transition). Further, I don't have a panel to test, just the
> PS8640.
> 
> thanks
> Philipp
> 
> 

Regards,
CK

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