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

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Message-ID: <7daeeaba-a33d-bf05-1371-d9b5fa0bf0a5@quicinc.com>
Date: Mon, 22 Apr 2024 10:23:18 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 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.
> 
>>
>>> Fixes: a2ab5d5bb6b1 ("drm/msm: allow passing struct msm_kms to msm_drv_probe()")

Actually, Is this Fixes tag correct?

OR is this one better

Fixes: 506efcba3129 ("drm/msm: carve out KMS code from msm_drv.c")


>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>> ---
>>>    drivers/gpu/drm/msm/msm_kms.c | 1 -
>>>    1 file changed, 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/msm_kms.c b/drivers/gpu/drm/msm/msm_kms.c
>>> index af6a6fcb1173..6749f0fbca96 100644
>>> --- a/drivers/gpu/drm/msm/msm_kms.c
>>> +++ b/drivers/gpu/drm/msm/msm_kms.c
>>> @@ -244,7 +244,6 @@ int msm_drm_kms_init(struct device *dev, const struct drm_driver *drv)
>>>    	ret = priv->kms_init(ddev);
>>>    	if (ret) {
>>>    		DRM_DEV_ERROR(dev, "failed to load kms\n");
>>> -		priv->kms = NULL;
>>>    		return ret;
>>>    	}
>>>
>