Re: [PATCH RESEND v9 0/6] MHDP8546 fixes related to DRM_BRIDGE_ATTACH_NO_CONNECTOR usecase

[Harikrishna shenoy <h-shenoy@ti.com>]

On 21/11/25 17:37, Tomi Valkeinen wrote:
> Hi,
> 
> On 20/11/2025 14:14, Harikrishna Shenoy wrote:
>> With the DRM_BRIDGE_ATTACH_NO_CONNECTOR framework, the connector is
>> no longer initialized in  bridge_attach() when the display controller
>> sets the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.
>> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn()
>> when trying to access &conn->dev->mode_config.mutex.
>> Observed on a board where EDID read failed.
>> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
>>
>> Patch 1 adds a connector_ptr which takes care of both
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR and !DRM_BRIDGE_ATTACH_NO_CONNECTOR
>> case by setting the pointer in appropriate hooks and checking for pointer
>> validity before accessing the connector.
>> Patch 2 adds mode validation hook to bridge fucntions.
>> Patch 3 fixes HDCP to work with both DRM_BRIDGE_ATTACH_NO_CONNECTOR
>> and !DRM_BRIDGE_ATTACH_NO_CONNECTOR case by moving HDCP state handling
>> into the bridge atomic check inline with the
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR model.
>> Patches 4,5 do necessary cleanup and alignment for using
>> connector pointer.
>>
>> The rationale behind the sequence of commits is we can cleanly
>> switch to drm_connector pointer after removal of connector helper
>> code blocks, which are anyways not touch after
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR has been enabled in driver.
>>
>> The last patch make smaller adjustment: lowering the log level for
>> noisy DPCD transfer errors.
>>
>> v8 patch link:
>> <https://lore.kernel.org/all/20251014094527.3916421-1-h-shenoy@ti.com/>
>>
>> Changelog v8-v9:
>> -Move the patch 6 in v8 related to HDCP to patch 3 and add fixes tag.
>> -Update to connector_ptr in HDCP code in patch 1.
>> -Rebased on next-20251114.
> 
> Don't base on linux-next, except in some quite special circumstances.
> Base on latest major version from Linus, or -rc from Linus, or
> drm-misc-next. Usually drm-misc-next is a safe choice for DRM patches.
> 
> And if you make changes to a series, it's not a "resend" but a new version.
> 
>   Tomi
> 
Hi Tomi,

Thanks for pointing it out, will re-spin next version v10 and base it on 
drm-misc-next.

Regards.

>>
>> v7 patch link:
>> <https://lore.kernel.org/all/20250929083936.1575685-1-h-shenoy@ti.com/>
>>
>> Changelog v7-v8:
>> -Move patches with firxes tag to top of series with appropriate changes
>> to them.
>> -Add R/B tag to patch
>> https://lore.kernel.org/all/ae3snoap64r252sbqhsshsadxfmlqdfn6b4o5fgfcmxppglkqf@2lsstfsghzwb/
>>
>> v6 patch link:
>> <https://lore.kernel.org/all/20250909090824.1655537-1-h-shenoy@ti.com/>
>>
>> Changelog v6-v7:
>> -Update cover letter to explain the series.
>> -Add R/B tag in PATCH 1 and drop fixes tag as suggested.
>> -Drop fixes tag in PATCH 2.
>> -Update the commit messages for clear understanding of changes done in patches.
>>
>> v5 patch link:
>> <https://lore.kernel.org/all/20250811075904.1613519-1-h-shenoy@ti.com/>
>>
>> Changelog v5 -> v6:
>> -Update cover letter to clarify the series in better way.
>> -Add Reviewed-by tag to relevant patches.
>>   
>> v4 patch link:
>> <https://lore.kernel.org/all/20250624054448.192801-1-j-choudhary@ti.com>
>>
>> Changelog v4->v5:
>> - Handle HDCP state in bridge atomic check instead of connector
>> atomic check
>>   
>> v3 patch link:
>> <https://lore.kernel.org/all/20250529142517.188786-1-j-choudhary@ti.com/>
>>
>> Changelog v3->v4:
>> - Fix kernel test robot build warning:
>>    <https://lore.kernel.org/all/202505300201.2s6r12yc-lkp@intel.com/>
>>
>> v2 patch link:
>> <https://lore.kernel.org/all/20250521073237.366463-1-j-choudhary@ti.com/>
>>
>> Changelog v2->v3:
>> - Add mode_valid in drm_bridge_funcs to a separate patch
>> - Remove "if (mhdp->connector.dev)" conditions that were missed in v2
>> - Split out the move of drm_atomic_get_new_connector_for_encoder()
>>    to a separate patch
>> - Drop "R-by" considering the changes in v2[1/3]
>> - Add Fixes tag to first 4 patches:
>>    commit c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
>>    This added DBANC flag in tidss while attaching bridge to the encoder
>> - Drop RFC prefix
>>
>> v1 patch link:
>> <https://lore.kernel.org/all/20250116111636.157641-1-j-choudhary@ti.com/>
>>
>> Changelog v1->v2:
>> - Remove !DRM_BRIDGE_ATTACH_NO_CONNECTOR entirely
>> - Add mode_valid in drm_bridge_funcs[0]
>> - Fix NULL POINTER differently since we cannot access atomic_state
>> - Reduce log level in cdns_mhdp_transfer call
>>
>> [0]: https://lore.kernel.org/all/20240530091757.433106-1-j-choudhary@ti.com/
>>
>> Harikrishna Shenoy (1):
>>    drm/bridge: cadence: cdns-mhdp8546-core: Handle HDCP state in bridge
>>      atomic check
>>
>> Jayesh Choudhary (5):
>>    drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector
>>      earlier in atomic_enable()
>>    drm/bridge: cadence: cdns-mhdp8546-core: Add mode_valid hook to
>>      drm_bridge_funcs
>>    drm/bridge: cadence: cdns-mhdp8546-core: Remove legacy support for
>>      connector initialisation in bridge
>>    drm/bridge: cadence: cdns-mhdp8546*: Change drm_connector from
>>      structure to pointer
>>    drm/bridge: cadence: cdns-mhdp8546-core: Reduce log level for DPCD
>>      read/write
>>
>>   .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 258 +++++-------------
>>   .../drm/bridge/cadence/cdns-mhdp8546-core.h   |   2 +-
>>   .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   |   8 +-
>>   3 files changed, 72 insertions(+), 196 deletions(-)
>>
>