Re: [PATCH] drm/xe: Convert xe_pm_runtime_{get,put} to void and protect from recursion

[Matthew Auld <matthew.auld@intel.com>]

On 27/02/2024 18:35, Rodrigo Vivi wrote:
> With mem_access going away and pm_runtime getting called instead,
> we need to protect these against recursions.
> 
> For D3cold, the TTM migration helpers will call for the job execution.
> Jobs execution will be protected by direct runtime_pm calls, but they
> cannot be called again if we are already at a runtime suspend/resume
> transaction when evicting/restoring memory for D3Cold. So, we will check
> for the xe_pm_read_callback_task.
> 
> The put is asynchronous so there's no need to block it. However, for a
> proper balance, we need to ensure that the references are taken and
> restored regardless of the flow. So, let's convert them all to void and
> use some direct linux/pm_runtime functions.
> 
> Cc: Matthew Auld <matthew.auld@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_pm.c | 25 ++++++++++++++-----------
>   drivers/gpu/drm/xe/xe_pm.h |  4 ++--
>   2 files changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index b5511e3c3153..3664480b21ba 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -408,26 +408,29 @@ int xe_pm_runtime_resume(struct xe_device *xe)
>   /**
>    * xe_pm_runtime_get - Get a runtime_pm reference and resume synchronously
>    * @xe: xe device instance
> - *
> - * Returns: Any number greater than or equal to 0 for success, negative error
> - * code otherwise.
>    */
> -int xe_pm_runtime_get(struct xe_device *xe)
> +void xe_pm_runtime_get(struct xe_device *xe)

Actually there is still the caller in intel_runtime_pm_get() compat. 
What is the correct patch order here? It's kind of hard to follow.

>   {
> -	return pm_runtime_get_sync(xe->drm.dev);
> +	pm_runtime_get_noresume(xe->drm.dev);
> +
> +	if (xe_pm_read_callback_task(xe) == current)
> +		return;
> +
> +	pm_runtime_resume(xe->drm.dev);
>   }
>   
>   /**
>    * xe_pm_runtime_put - Put the runtime_pm reference back and mark as idle
>    * @xe: xe device instance
> - *
> - * Returns: Any number greater than or equal to 0 for success, negative error
> - * code otherwise.
>    */
> -int xe_pm_runtime_put(struct xe_device *xe)
> +void xe_pm_runtime_put(struct xe_device *xe)
>   {
> -	pm_runtime_mark_last_busy(xe->drm.dev);
> -	return pm_runtime_put(xe->drm.dev);
> +	if (xe_pm_read_callback_task(xe) == current) {
> +		pm_runtime_put_noidle(xe->drm.dev);
> +	} else {
> +		pm_runtime_mark_last_busy(xe->drm.dev);
> +		pm_runtime_put(xe->drm.dev);
> +	}
>   }
>   
>   /**
> diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h
> index 7f5884babb29..fdc2a49c1a1f 100644
> --- a/drivers/gpu/drm/xe/xe_pm.h
> +++ b/drivers/gpu/drm/xe/xe_pm.h
> @@ -26,9 +26,9 @@ void xe_pm_runtime_fini(struct xe_device *xe);
>   bool xe_pm_runtime_suspended(struct xe_device *xe);
>   int xe_pm_runtime_suspend(struct xe_device *xe);
>   int xe_pm_runtime_resume(struct xe_device *xe);
> -int xe_pm_runtime_get(struct xe_device *xe);
> +void xe_pm_runtime_get(struct xe_device *xe);
>   int xe_pm_runtime_get_ioctl(struct xe_device *xe);
> -int xe_pm_runtime_put(struct xe_device *xe);
> +void xe_pm_runtime_put(struct xe_device *xe);
>   int xe_pm_runtime_get_if_active(struct xe_device *xe);
>   void xe_pm_assert_unbounded_bridge(struct xe_device *xe);
>   int xe_pm_set_vram_threshold(struct xe_device *xe, u32 threshold);