[PATCH v2] drm/xe/client: Check return value of xe_force_wake_get

[Ghimiray, Himal Prasad]

On 03-06-2024 14:01, Nirmoy Das wrote:
> xe_force_wake_get() can return error so check it's return value
> before reading gpu_timestamp value.
>
> v2: set HWE to NULL instead of setting timestamp to 0(Lucas)
>      Add a warn on for xe_force_wake_put(Himal)
>
> Fixes: 188ced1e0ff8 ("drm/xe/client: Print runtime to fdinfo")
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>   drivers/gpu/drm/xe/xe_drm_client.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_drm_client.c b/drivers/gpu/drm/xe/xe_drm_client.c
> index 4a19b771e3a0..4bdb909eabfc 100644
> --- a/drivers/gpu/drm/xe/xe_drm_client.c
> +++ b/drivers/gpu/drm/xe/xe_drm_client.c
> @@ -264,9 +264,13 @@ static void show_run_ticks(struct drm_printer *p, struct drm_file *file)
>   		if (!hwe)
>   			continue;
>   
> -		xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
> +		if (xe_force_wake_get(gt_to_fw(gt), XE_FW_GT)) {

Since xe_force_wake_get will increase the ref count irrespective of 
acknowledgment from forcewake ack register fails or succeeds.

It is required to decrement the ref count taken by xe_force_wake_get by 
calling xe_force_wake_put before break.

something like :

if (xe_force_wake_get(gt_to_fw(gt), XE_FW_GT))

hwe = NULL;

else

gpu_timestamp = xe_hw_engine_read_timestamp(hwe);

XE_WARN_ON(xe_force_wake_put(gt_to_fw(gt), XE_FW_GT));


> +			hwe = NULL;
> +			break;
> +		}
> +
>   		gpu_timestamp = xe_hw_engine_read_timestamp(hwe);
> -		xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
> +		XE_WARN_ON(xe_force_wake_put(gt_to_fw(gt), XE_FW_GT));
>   		break;
>   	}
>