Re: [PATCH] drm/xe/pm: Change HPD to polling on runtime suspend

[Imre Deak <imre.deak@intel.com>]

On Tue, Aug 06, 2024 at 02:25:13PM +0530, Arun R Murthy wrote:
> HPD is interrupt based and on runtime suspend change it to polling as
> HPD is not a wakeup event. A worker thread is scheduled for doing this
> polling and it keeps polling for HPD live status on an internval of 10s.
> On runtime resume disable polling and fallback to interrupt mechanism.
> 
> Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pm.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index 9f3c14fd9f33..d952b06ebfb4 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -22,6 +22,7 @@
>  #include "xe_pcode.h"
>  #include "xe_trace.h"
>  #include "xe_wa.h"
> +#include "intel_hotplug.h"
>  
>  /**
>   * DOC: Xe Power Management
> @@ -378,6 +379,8 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
>  		if (err)
>  			goto out;
>  	}
> +	/* Enable hpd polling on runtime suspend */
> +	intel_hpd_poll_enable(xe);
>  
>  	xe_irq_suspend(xe);
>  
> @@ -427,6 +430,9 @@ int xe_pm_runtime_resume(struct xe_device *xe)
>  
>  	xe_irq_resume(xe);
>  
> +	/* Disable hpd polling on runtime resume */
> +	intel_hpd_poll_disable(xe);

This should be handled in xe_display_pm_resume() (likewise enabling
polling in xe_display_pm_suspend()), in fact it's already called there.
Also this is missing the xe->info.enable_display check and polling
shouldn't be enabled when system (vs. runtime) suspending.

Not sure why the display is suspended/resumed only if d3cold is allowed,
for many of the display s/r steps at least it doesn't make sense to me.
For now moving the d3cold check within
xe_display_pm_suspend()/resume() and enabling/disabling polling
regardless of that flag would be the simplest imo.

> +
>  	for_each_gt(gt, xe, id)
>  		xe_gt_resume(gt);
>  
> -- 
> 2.25.1
>