linux-kernel - Re: [PATCH 1/3] drm/msm: don't clean up priv->kms prematurely

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Message-ID: <ohzwt5llvvogo46757iemkrnqwdzwqldi3bhbgvk4pxsp3wpuo@enc4bzir3uur>
Date: Mon, 22 Apr 2024 22:44:44 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/msm: don't clean up priv->kms prematurely

On Mon, Apr 22, 2024 at 09:12:20AM -0700, Abhinav Kumar wrote:
> 
> 
> On 4/21/2024 3:35 PM, Dmitry Baryshkov wrote:
> > On Sat, Apr 20, 2024 at 04:02:00PM -0700, Abhinav Kumar wrote:
> > > 
> > > 
> > > On 4/19/2024 7:33 PM, Dmitry Baryshkov wrote:
> > > > MSM display drivers provide kms structure allocated during probe().
> > > > Don't clean up priv->kms field in case of an error. Otherwise probe
> > > > functions might fail after KMS probe deferral.
> > > > 
> > > 
> > > So just to understand this more, this will happen when master component
> > > probe (dpu) succeeded but other sub-component probe (dsi) deferred?
> > > 
> > > Because if master component probe itself deferred it will allocate priv->kms
> > > again isnt it and we will not even hit here.
> > 
> > Master probing succeeds (so priv->kms is set), then kms_init fails at
> > runtime, during binding of the master device. This results in probe
> > deferral from the last component's component_add() function and reprobe
> > attempt when possible (once the next device is added or probed). However
> > as priv->kms is NULL, probe crashes.
> > 
> 
> Got it, a better commit text would have helped here. Either way,

I'll update the commit text with the text above.

> 
> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>

-- 
With best wishes
Dmitry