linux-kernel - Re: [PATCH v7 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic

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Message-ID: <429400d3-e369-cf6a-3e9c-3d00622d7f29@ti.com>
Date: Fri, 10 Oct 2025 14:48:10 +0530
From: Harikrishna shenoy <h-shenoy@...com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
CC: <andrzej.hajda@...el.com>, <neil.armstrong@...aro.org>, <rfoss@...nel.org>,
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Subject: Re: [PATCH v7 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the
 mhdp connector earlier in atomic_enable()



On 06/10/25 04:42, Dmitry Baryshkov wrote:
> On Mon, Sep 29, 2025 at 02:09:33PM +0530, Harikrishna Shenoy wrote:
>> From: Jayesh Choudhary <j-choudhary@...com>
>>
>> In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
>> in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
>> NULL pointer while trying to access the mutex. We need the connector to
>> be set before that. Unlike in legacy !(DBANC) cases, we do not have
>> connector initialised in bridge_attach(). Now that we have the connector
>> pointer in mhdp bridge structure, so set the mhdp->connector in
>> atomic_enable() earlier to avoid possible NULL pointer dereference
>> in recovery paths like modeset_retry_fn() with the DBANC flag set.
>>
>> Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
> 
> This Fixes tag means that this patch can be attempted to be backported
> back to v6.5 (even w/o cc:stable, etc). I know that it is a pain, but
> please move all Fixes to the top of the series. Yes, you want to drop
> non-DBANC case first and then fix everything. It doesn't look like it is
> a correct approach for the sake of maintaing the -stable branches.
> 
Hi Dmitry,

The patch which drops non-DBANC case can be moved after fixes, but for
making fixes i need the pointer structure so adding fixes tag to PATCH 
2/6 "drm/bridge: cadence: cdns-mhdp8546*: Change
  drm_connector from structure to pointer"
Let me know your thoughts on this, will re-spin accordingly.

Regards.

>> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
>> Signed-off-by: Harikrishna Shenoy <h-shenoy@...com>
>> ---
>>   .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 20 +++++++++----------
>>   1 file changed, 10 insertions(+), 10 deletions(-)
>>
>