linux-kernel - Re: [PATCH v7 6/7] drm/msm/hdmi: also send the SPD and HDMI Vendor Specific InfoFrames

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Message-ID: <ry2jfdxhbogl42wbiajll5et5n2puvu46fn25v25qwpac7bbyu@wvhz3ijtfd56>
Date: Sat, 8 Feb 2025 05:24:29 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, Simona Vetter <simona@...ll.ch>, 
	Simona Vetter <simona.vetter@...ll.ch>, dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 6/7] drm/msm/hdmi: also send the SPD and HDMI Vendor
 Specific InfoFrames

On Fri, Feb 07, 2025 at 07:05:14PM -0800, Abhinav Kumar wrote:
> 
> 
> On 2/7/2025 6:04 PM, Dmitry Baryshkov wrote:
> > On Fri, Feb 07, 2025 at 05:31:20PM -0800, Abhinav Kumar wrote:
> > > 
> > > 
> > > On 2/7/2025 4:27 PM, Dmitry Baryshkov wrote:
> > > > Extend the driver to send SPD and HDMI Vendor Specific InfoFrames.
> > > > 
> > > > While the HDMI block has special block to send HVS InfoFrame, use
> > > > GENERIC0 block instead. VENSPEC_INFO registers pack frame data in a way
> > > > that requires manual repacking in the driver, while GENERIC0 doesn't
> > > > have such format requirements. The msm-4.4 kernel uses GENERIC0 to send
> > > > HDR InfoFrame which we do not at this point anyway.
> > > > 
> > > 
> > > True that GENERIC_0/1 packets can be used for any infoframe. But because we
> > > have so many of them, thats why when there are dedicated registers for some
> > > of them, we use them to save the GENERIC0 ones for others.
> > 
> > True
> > 
> > > Lets take a case where we want to send HVSIF, SPD and HDR together for the
> > > same frame, then we run out as there are no HDR specific infoframe registers
> > > we can use. Is the expectation that we will migrate to VENSPEC_INFO regs for
> > > HVSIF when we add HDR support?
> > 
> > Most likely, yes. That would be a part of the HDR support. At the same
> > time note, we can use GENERIC0 to send new HFVS InfoFrames defined in
> > HDMI 2.x (once Linux gets support for that). At the same time we can not
> > use VENSPEC_INFO to send those.
> > 
> > I can imagine that the driver will have to switch GENERIC1 between HDR
> > (if required) and SPD (in all other cases).
> > 
> 
> We dont have to use GENERIC0 for HFVS infoframes. We have dedicated
> HFVS_INFO registers for those.

Ack, I have been checking the old (apq8064) chipset.

> 
> > > 
> > > Also from a validation standpoint, I guess to really validate this change
> > > you need an analyzer which decodes the HVSIF. So was this mostly sanity
> > > tested at this pointed to make sure that the sink just comes up?
> > 
> > Vertex 2 dumps received HVS InfoFrame, so the InfoFrame contents has
> > been validated (validated SPD, AUD, HVS and AVI frames).
> > 
> 
> Yup, vertex2 validation is perfect for this!
> 
> Overall, I am fine with this,
> 
> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>

-- 
With best wishes
Dmitry