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

[Daniel Kurtz]

On Thu, Feb 4, 2016 at 2:37 PM, CK Hu <ck.hu at mediatek.com> wrote:
> 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().

Then what about the other direction?
Should we be powering up dsi first before enabling the panel so DSI
can receive an panel enabling errors?

-Dan

>
>> 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
>