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

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Mika Kahola <mika.kahola@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/2] drm/i915/dsi: Send SHUTDOWN only for v3+ VBT's
Date: Mon, 4 Sep 2017 18:04:49 +0300	[thread overview]
Message-ID: <20170904150449.GE4914@intel.com> (raw)
In-Reply-To: <1504511972.12240.20.camel@intel.com>

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?

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).

> 
> > 
> > > 
> > > 
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102404
> > > Signed-off-by: Mika Kahola <mika.kahola@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@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> -- 
> Mika Kahola - Intel OTC

-- 
Ville Syrjälä
Intel OTC
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