Re: [PATCH v5 01/23] drm/xe: Error handling in xe_force_wake_get()

["Nilawar, Badal" <badal.nilawar@intel.com>]

Hi Himal,

On 24-09-2024 17:46, Himal Prasad Ghimiray wrote:
> If an acknowledgment timeout occurs for a domain awake request, do not

s/acknowledgement/forcewake acknowledgement/

> increment the reference count for the domain. This ensures that
> subsequent _get calls do not incorrectly assume the domain is awake. The
> return value is a mask of domains whose reference counts were
> incremented, and these domains need to be released using
> xe_force_wake_put.
> 
> The caller needs to compare the return value with the input domains to
> determine the success or failure of the operation and decide whether to
> continue or return accordingly.
> 
> While at it, add simple kernel-doc for xe_force_wake_get()
> 
> v3
> - Use explicit type for mask (Michal/Badal)
> - Improve kernel-doc (Michal)
> - Use unsigned int instead of abusing enum (Michal)
> 
> v5
> - Use unsigned int for return (MattB/Badal/Rodrigo)
> - use xe_gt_WARN for domain awake ack failure (Badal/Rodrigo)
> 
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Badal Nilawar <badal.nilawar@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Nirmoy Das <nirmoy.das@intel.com>
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_force_wake.c | 37 +++++++++++++++++++++++-------
>   drivers/gpu/drm/xe/xe_force_wake.h |  4 ++--
>   2 files changed, 31 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_force_wake.c b/drivers/gpu/drm/xe/xe_force_wake.c
> index a64c14757c84..d190aa93be90 100644
> --- a/drivers/gpu/drm/xe/xe_force_wake.c
> +++ b/drivers/gpu/drm/xe/xe_force_wake.c
> @@ -150,28 +150,49 @@ static int domain_sleep_wait(struct xe_gt *gt,
>   					 (ffs(tmp__) - 1))) && \
>   					 domain__->reg_ctl.addr)
>   
> -int xe_force_wake_get(struct xe_force_wake *fw,
> -		      enum xe_force_wake_domains domains)
> +/**
> + * xe_force_wake_get() : Increase the domain refcount
> + * @fw: struct xe_force_wake
> + * @domains: forcewake domains to get refcount on
> + *
> + * This function takes references for the input @domains and wakes them if
> + * they are asleep.
> + *
> + * Return: mask of refcount increased domains. If the return value is
> + * equal to the input parameter @domains, the operation is considered
> + * successful. Otherwise, the operation is considered a failure, and
> + * the caller should handle the failure case, potentially returning
> + * -ETIMEDOUT.
> + */

Here especially for FORCEWAKE_ALL case caller has to strictly compare 
return mask with FORCEWAKE_ALL instead of just if(!ret) and return. 
Which is fine.

> +unsigned int xe_force_wake_get(struct xe_force_wake *fw,
> +			       enum xe_force_wake_domains domains)
>   {
>   	struct xe_gt *gt = fw->gt;
>   	struct xe_force_wake_domain *domain;
> -	enum xe_force_wake_domains tmp, woken = 0;
> +	unsigned int tmp, ret, awake_rqst = 0, awake_failed = 0;
>   	unsigned long flags;
> -	int ret = 0;
>   
>   	spin_lock_irqsave(&fw->lock, flags);
>   	for_each_fw_domain_masked(domain, domains, fw, tmp) {
>   		if (!domain->ref++) {
> -			woken |= BIT(domain->id);
> +			awake_rqst |= BIT(domain->id);
>   			domain_wake(gt, domain);
>   		}
>   	}
> -	for_each_fw_domain_masked(domain, woken, fw, tmp) {
> -		ret |= domain_wake_wait(gt, domain);
> +	for_each_fw_domain_masked(domain, awake_rqst, fw, tmp) {
> +		if (domain_wake_wait(gt, domain) == 0) {
> +			fw->awake_domains |= BIT(domain->id);
> +		} else {
> +			awake_failed |= BIT(domain->id);
> +			--domain->ref;
> +		}
>   	}
> -	fw->awake_domains |= woken;
> +	ret = (domains & ~awake_failed);
>   	spin_unlock_irqrestore(&fw->lock, flags);
>   
> +	xe_gt_WARN(gt, awake_failed, "domain%s %#x failed to acknowledgment awake\n",

Forcewake domain%s failed to acknowledge awake request.

> +		   str_plural(hweight_long(awake_failed)), awake_failed);
> +
>   	return ret;
>   }
>   
> diff --git a/drivers/gpu/drm/xe/xe_force_wake.h b/drivers/gpu/drm/xe/xe_force_wake.h
> index a2577672f4e3..6c1ade39139b 100644
> --- a/drivers/gpu/drm/xe/xe_force_wake.h
> +++ b/drivers/gpu/drm/xe/xe_force_wake.h
> @@ -15,8 +15,8 @@ void xe_force_wake_init_gt(struct xe_gt *gt,
>   			   struct xe_force_wake *fw);
>   void xe_force_wake_init_engines(struct xe_gt *gt,
>   				struct xe_force_wake *fw);
> -int xe_force_wake_get(struct xe_force_wake *fw,
> -		      enum xe_force_wake_domains domains);
> +unsigned int xe_force_wake_get(struct xe_force_wake *fw,
> +			       enum xe_force_wake_domains domains);

Looks good to me.
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>

Regards,
Badal

>   int xe_force_wake_put(struct xe_force_wake *fw,
>   		      enum xe_force_wake_domains domains);
>