[Intel-gfx] [PATCH 1/2] drm/i915/dsi: Send SHUTDOWN only for v3+ VBT's

Tue Sep 5 15:10:34 UTC 2017

On Tue, Sep 05, 2017 at 02:55:31PM +0000, Shankar, Uma wrote:
> 
> 
> >-----Original Message-----
> >From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
> >Sent: Tuesday, September 5, 2017 6:46 PM
> >To: Shankar, Uma <uma.shankar at intel.com>
> >Cc: Kahola, Mika <mika.kahola at intel.com>; Srinivas, Vidya
> ><vidya.srinivas at intel.com>; intel-gfx at lists.freedesktop.org
> >Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915/dsi: Send SHUTDOWN only for v3+
> >VBT's
> >
> >On Tue, Sep 05, 2017 at 09:27:47AM +0000, Shankar, Uma wrote:
> >>
> >>
> >> >-----Original Message-----
> >> >From: Kahola, Mika
> >> >Sent: Tuesday, September 5, 2017 2:03 PM
> >> >To: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> >Cc: intel-gfx at lists.freedesktop.org; Shankar, Uma
> >> ><uma.shankar at intel.com>
> >> >Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915/dsi: Send SHUTDOWN only
> >> >for v3+ VBT's
> >> >
> >> >On Mon, 2017-09-04 at 18:04 +0300, Ville Syrjälä wrote:
> >> >> On Mon, Sep 04, 2017 at 10:59:32AM +0300, Mika Kahola wrote:
> >> >> >
> >> >> > On Fri, 2017-09-01 at 16:43 +0300, Ville Syrjälä wrote:
> >> >> > >
> >> >> > > On Fri, Sep 01, 2017 at 10:51:00AM +0300, Mika Kahola wrote:
> >> >> > > >
> >> >> > > >
> >> >> > > > According to spec we should send SHUTDOWN before
> >> >> > > > MIPI_SEQ_DISPLAY_OFF for
> >> >> > > > v3+ VBT's. Testing with VBT v3 the current implementation
> >> >> > > > yields
> >> >> > > > the
> >> >> > > > following error message
> >> >> > > >
> >> >> > > > *ERROR* Video mode command 0x00000041 send failed.
> >> >> > > >
> >> >> > > > To get rid of this error message, let's limit SHUTDOWN only
> >> >> > > > for VBT versions 3 or higher.
> >> >> > > In the patch you limit it to version 4+, which doesn't make
> >> >> > > sense since AFAIK there is no version 4 of the sequence block.
> >> >> > It seems that sending SHUTDOWN signal doesn't make any sense either.
> >> >> > Whenever we send that signal it just causes this error message.
> >> >> > Do we really need to signal this? From functionality point of
> >> >> > view there's no difference.
> >> >> Well, the spec doesn't even explain what this "shut down" command
> >> >> does.
> >> >> Is it actually the DCS "display off" command, or something else?
> >> >It seems to do something. At least the intel_wait_for_register()
> >> >times out when sending SHUTDOWN signal. Maybe it just shuts down
> >> >display so we can't even read the registers after that.
> >> >
> >> >This brings me to another idea. Maybe we should skip
> >> >intel_wait_for_register() if we have sent out SHUTDOWN signal?
> >> >
> >> >>
> >> >> Did you try reverting bbdf0b2ff32a ("drm/i915/bxt: Disable device
> >> >> ready before shutdown command")? That looks suspicious to me. But
> >> >> so does about half of the DSI code since it never seems to follow
> >> >> the spec, and we end up doing totally different things on different
> >> >> platforms without any explanation why that is).
> >> >I haven't tried that. I will give it a go and see what happens.
> >> >
> >>
> >> The issue is happening due to Device Ready setting. It was added to
> >> resolve a DSI split screen issue in  dual link DSI panels. Since DSI
> >> dual link is not enabled and will require a bit of work in upstream,
> >> we should revert this change. Vidya will  send the change and also work on
> >enabling dual link support in upstream.
> >>
> >> FYI - SHUTDOWN is a short packet peripheral command that turns off the
> >> display in a Video Mode display module for power saving.
> >
> >There is no SHUTDOWN comamnd in the DCS spec that I can find.
> >
> 
> Hi Ville,
> It's part of MIPI_DSI_specification - (v1-3 is the latest)
> 8.8.5 Shutdown Peripheral Command, Data Type = 10 0010 (0x22)
> Shutdown Peripheral command is a Short packet command that turns off the display
> in a Video Mode display module for power saving. Note the interface shall remain powered
> in order to receive the turn-on,  or wake-up, command.

Ah, thanks. I was only looking at the DCS spec.

> 
> Regards,
> Uma Shankar
> 
> >>
> >> For DSI, there have been issues with different panels requiring some
> >> unconventional changes, and also bspec sometimes doesn't cover
> >> everything generically.  So, it gets a bit challenging :(
> >>
> >> Regards,
> >> Uma Shankar
> >>
> >> >> >
> >> >> >
> >> >> > >
> >> >> > >
> >> >> > > >
> >> >> > > >
> >> >> > > >
> >> >> > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102404
> >> >> > > > Signed-off-by: Mika Kahola <mika.kahola at intel.com>
> >> >> > > > ---
> >> >> > > >  drivers/gpu/drm/i915/intel_dsi.c | 2 +-
> >> >> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> >> >> > > >
> >> >> > > > diff --git a/drivers/gpu/drm/i915/intel_dsi.c
> >> >> > > > b/drivers/gpu/drm/i915/intel_dsi.c
> >> >> > > > index 2a0f5d3..b48b9b7 100644
> >> >> > > > --- a/drivers/gpu/drm/i915/intel_dsi.c
> >> >> > > > +++ b/drivers/gpu/drm/i915/intel_dsi.c
> >> >> > > > @@ -916,7 +916,7 @@ static void intel_dsi_disable(struct
> >> >> > > > intel_encoder *encoder,
> >> >> > > >  	 * MIPI_SEQ_DISPLAY_OFF only for v3+ VBTs, but field testing
> >> >> > > >  	 * has shown that the v3 sequence works for v2 VBTs too
> >> >> > > >  	 */
> >> >> > > > -	if (is_vid_mode(intel_dsi)) {
> >> >> > > > +	if (is_vid_mode(intel_dsi) && dev_priv-
> >> >> > > > >
> >> >> > > > > vbt.dsi.seq_version > 3) {
> >> >> > > >  		/* Send Shutdown command to the panel in LP mode */
> >> >> > > >  		for_each_dsi_port(port, intel_dsi->ports)
> >> >> > > >  			dpi_send_cmd(intel_dsi, SHUTDOWN, false,
> >port);
> >> >> > > > --
> >> >> > > > 2.7.4
> >> >> > > >
> >> >> > > > _______________________________________________
> >> >> > > > Intel-gfx mailing list
> >> >> > > > Intel-gfx at lists.freedesktop.org
> >> >> > > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >> >> > --
> >> >> > Mika Kahola - Intel OTC
> >> >--
> >> >Mika Kahola - Intel OTC
> >>
> >
> >--
> >Ville Syrjälä
> >Intel OTC

-- 
Ville Syrjälä
Intel OTC