[Freedreno] [PATCH v2 2/2] drm/msm/dp: attach the DP subconnector property

[Johan Hovold]

On Wed, Oct 25, 2023 at 12:23:10PM +0300, Dmitry Baryshkov wrote:
> While developing and testing the commit bfcc3d8f94f4 ("drm/msm/dp:
> support setting the DP subconnector type") I had the patch [1] in my
> tree. I haven't noticed that it was a dependency for the commit in
> question. Mea culpa.

This also broke boot on the Lenovo ThinkPad X13s.

Would be nice to get this fixed ASAP so that further people don't have
to debug this known regression.
 
> Since the patch has not landed yet (and even was not reviewed)
> and since one of the bridges erroneously uses USB connector type instead
> of DP, attach the property directly from the MSM DP driver.
> 
> This fixes the following oops on DP HPD event:
> 
>  drm_object_property_set_value (drivers/gpu/drm/drm_mode_object.c:288)
>  dp_display_process_hpd_high (drivers/gpu/drm/msm/dp/dp_display.c:402)
>  dp_hpd_plug_handle.isra.0 (drivers/gpu/drm/msm/dp/dp_display.c:604)
>  hpd_event_thread (drivers/gpu/drm/msm/dp/dp_display.c:1110)
>  kthread (kernel/kthread.c:388)
>  ret_from_fork (arch/arm64/kernel/entry.S:858)

This only says where the oops happened, it doesn't necessarily in itself
indicate an oops at all or that in this case it's a NULL pointer
dereference.

On the X13s I'm seeing the NULL deref in a different path during boot,
and when this happens after a deferred probe (due to the panel lookup
mess) it hangs the machine, which makes it a bit of a pain to debug:

   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000060
   ...
   CPU: 4 PID: 57 Comm: kworker/u16:1 Not tainted 6.7.0-rc1 #4
   Hardware name: Qualcomm QRD, BIOS 6.0.220110.BOOT.MXF.1.1-00470-MAKENA-1 01/10/2022
   ...
   Call trace:
    drm_object_property_set_value+0x0/0x88 [drm]
    dp_display_process_hpd_high+0xa0/0x14c [msm]
    dp_hpd_plug_handle.constprop.0.isra.0+0x90/0x110 [msm]
    dp_bridge_atomic_enable+0x184/0x21c [msm]
    edp_bridge_atomic_enable+0x60/0x94 [msm]
    drm_atomic_bridge_chain_enable+0x54/0xc8 [drm]
    drm_atomic_helper_commit_modeset_enables+0x194/0x26c [drm_kms_helper]
    msm_atomic_commit_tail+0x204/0x804 [msm]
    commit_tail+0xa4/0x18c [drm_kms_helper]
    drm_atomic_helper_commit+0x19c/0x1b0 [drm_kms_helper]
    drm_atomic_commit+0xa4/0x104 [drm]
    drm_client_modeset_commit_atomic+0x22c/0x298 [drm]
    drm_client_modeset_commit_locked+0x60/0x1c0 [drm]
    drm_client_modeset_commit+0x30/0x58 [drm]
    __drm_fb_helper_restore_fbdev_mode_unlocked+0xbc/0xfc [drm_kms_helper]
    drm_fb_helper_set_par+0x30/0x4c [drm_kms_helper]
    fbcon_init+0x224/0x49c
    visual_init+0xb0/0x108
    do_bind_con_driver.isra.0+0x19c/0x38c
    do_take_over_console+0x140/0x1ec
    do_fbcon_takeover+0x6c/0xe4
    fbcon_fb_registered+0x180/0x1f0
    register_framebuffer+0x19c/0x228
    __drm_fb_helper_initial_config_and_unlock+0x2e8/0x4e8 [drm_kms_helper]
    drm_fb_helper_initial_config+0x3c/0x4c [drm_kms_helper]
    msm_fbdev_client_hotplug+0x84/0xcc [msm]
    drm_client_register+0x5c/0xa0 [drm]
    msm_fbdev_setup+0x94/0x148 [msm]
    msm_drm_bind+0x3d0/0x42c [msm]
    try_to_bring_up_aggregate_device+0x1ec/0x2f4
    __component_add+0xa8/0x194
    component_add+0x14/0x20
    dp_display_probe+0x278/0x41c [msm]

> [1] https://patchwork.freedesktop.org/patch/555530/
> 
> Fixes: bfcc3d8f94f4 ("drm/msm/dp: support setting the DP subconnector type")
> Reviewed-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>

Reviewed-by: Johan Hovold <johan+linaro at kernel.org>
Tested-by: Johan Hovold <johan+linaro at kernel.org>

Johan