Re: [PATCH v5 1/3] drm/xe: Move LNL scheduling WA to xe_device.h

[John Harrison <john.c.harrison@intel.com>]

On 10/29/2024 05:01, Nirmoy Das wrote:
> Move LNL scheduling WA to xe_device.h so this can be used in other
> places without needing keep the same comment about removal of this WA
> in the future. The WA, which flushes work or workqueues, is now wrapped
> in macros and can be reused wherever needed.
>
> Cc: Badal Nilawar <badal.nilawar@intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> cc: <stable@vger.kernel.org> # v6.11+
> Suggested-by: John Harrison <John.C.Harrison@Intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_device.h | 14 ++++++++++++++
>   drivers/gpu/drm/xe/xe_guc_ct.c | 11 +----------
>   2 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
> index 4c3f0ebe78a9..f1fbfe916867 100644
> --- a/drivers/gpu/drm/xe/xe_device.h
> +++ b/drivers/gpu/drm/xe/xe_device.h
> @@ -191,4 +191,18 @@ void xe_device_declare_wedged(struct xe_device *xe);
>   struct xe_file *xe_file_get(struct xe_file *xef);
>   void xe_file_put(struct xe_file *xef);
>   
> +/*
> + * Occasionally it is seen that the G2H worker starts running after a delay of more than
> + * a second even after being queued and activated by the Linux workqueue subsystem. This
> + * leads to G2H timeout error. The root cause of issue lies with scheduling latency of
> + * Lunarlake Hybrid CPU. Issue disappears if we disable Lunarlake atom cores from BIOS
> + * and this is beyond xe kmd.
> + *
> + * TODO: Drop this change once workqueue scheduling delay issue is fixed on LNL Hybrid CPU.
> + */
> +#define LNL_FLUSH_WORKQUEUE(wq__) \
> +	flush_workqueue(wq__)
> +#define LNL_FLUSH_WORK(wrk__) \
> +	flush_work(wrk__)
> +
>   #endif
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 1b5d8fb1033a..703b44b257a7 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -1018,17 +1018,8 @@ static int guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
>   
>   	ret = wait_event_timeout(ct->g2h_fence_wq, g2h_fence.done, HZ);
>   
> -	/*
> -	 * Occasionally it is seen that the G2H worker starts running after a delay of more than
> -	 * a second even after being queued and activated by the Linux workqueue subsystem. This
> -	 * leads to G2H timeout error. The root cause of issue lies with scheduling latency of
> -	 * Lunarlake Hybrid CPU. Issue dissappears if we disable Lunarlake atom cores from BIOS
> -	 * and this is beyond xe kmd.
> -	 *
> -	 * TODO: Drop this change once workqueue scheduling delay issue is fixed on LNL Hybrid CPU.
> -	 */
>   	if (!ret) {
> -		flush_work(&ct->g2h_worker);
> +		LNL_FLUSH_WORK(&ct->g2h_worker);
>   		if (g2h_fence.done) {
>   			xe_gt_warn(gt, "G2H fence %u, action %04x, done\n",
>   				   g2h_fence.seqno, action[0]);
This message is still wrong.

We have a warning that says 'job completed successfully'! That is 
misleading. It needs to say "done after flush" or "done but flush was 
required" or something along those lines.

John.