Re: [PATCH 1/2] drm/xe/display: Do not suspend resume dp mst during runtime

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Sep 12, 2024 at 06:55:44AM +0530, Suraj Kandpal wrote:
> Remove intel_dp_mst_suspend/resume from runtime suspend resume
> sequences. It is incorrect as it depends on AUX transfers which
> itself depend on the device being runtime resumed. This is
> also why we see a lock_dep splat here.
> 
> <4> [76.011119] kworker/4:2/192 is trying to acquire lock:
> <4> [76.011122] ffff8881120b3210 (&mgr->lock#2){+.+.}-{3:3}, at:
> drm_dp_mst_topology_mgr_suspend+0x33/0xd0 [drm_display_helper]
> <4> [76.011142]
> but task is already holding lock:
> <4> [76.011144] ffffffffa0bc3420
> (xe_pm_runtime_lockdep_map){+.+.}-{0:0}, at:
> xe_pm_runtime_suspend+0x51/0x3f0 [xe]
> <4> [76.011223]
> which lock already depends on the new lock.
> <4> [76.011226]
> the existing dependency chain (in reverse order) is:
> <4> [76.011229]
> -> #2 (xe_pm_runtime_lockdep_map){+.+.}-{0:0}:
> <4> [76.011233]        pm_runtime_lockdep_prime+0x2f/0x50 [xe]
> <4> [76.011306]        xe_pm_runtime_resume_and_get+0x29/0x90 [xe]
> <4> [76.011377]        intel_display_power_get+0x24/0x70 [xe]
> <4> [76.011466]        intel_digital_port_connected_locked+0x4c/0xf0
> [xe]
> <4> [76.011551]        intel_dp_aux_xfer+0xb8/0x7c0 [xe]
> <4> [76.011633]        intel_dp_aux_transfer+0x166/0x2e0 [xe]
> <4> [76.011715]        drm_dp_dpcd_access+0x87/0x150
> [drm_display_helper]
> <4> [76.011726]        drm_dp_dpcd_probe+0x3d/0xf0 [drm_display_helper]
> <4> [76.011737]        drm_dp_dpcd_read+0xdd/0x130 [drm_display_helper]
> <4> [76.011747]        intel_dp_get_colorimetry_status+0x3a/0x70 [xe]
> <4> [76.011886]        intel_dp_init_connector+0x4ff/0x1030 [xe]
> <4> [76.011969]        intel_ddi_init+0xc5b/0x1030 [xe]
> <4> [76.012058]        intel_bios_for_each_encoder+0x36/0x60 [xe]
> <4> [76.012145]        intel_setup_outputs+0x201/0x460 [xe]
> <4> [76.012233]        intel_display_driver_probe_nogem+0x155/0x1e0 [xe]
> <4> [76.012320]        xe_display_init_noaccel+0x27/0x70 [xe]

could you please share the full in a link with me?
I believe we can improve this. This seems incomplete...

> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/xe/display/xe_display.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c
> index e65e7d70f989..39da79069b5a 100644
> --- a/drivers/gpu/drm/xe/display/xe_display.c
> +++ b/drivers/gpu/drm/xe/display/xe_display.c
> @@ -331,7 +331,8 @@ static void __xe_display_pm_suspend(struct xe_device *xe, bool runtime)
>  
>  	xe_display_flush_cleanup_work(xe);
>  
> -	intel_dp_mst_suspend(xe);
> +	if (!runtime)
> +		intel_dp_mst_suspend(xe);
>  
>  	intel_hpd_cancel_work(xe);
>  
> @@ -444,7 +445,9 @@ static void __xe_display_pm_resume(struct xe_device *xe, bool runtime)
>  		intel_display_driver_resume_access(xe);
>  
>  	/* MST sideband requires HPD interrupts enabled */
> -	intel_dp_mst_resume(xe);
> +	if (!runtime)
> +		intel_dp_mst_resume(xe);
> +
>  	if (!runtime && has_display(xe)) {
>  		intel_display_driver_resume(xe);
>  		drm_kms_helper_poll_enable(&xe->drm);
> -- 
> 2.43.2
>