Re: [PATCH 01/11] drm/i915: Decouple GuC log setup from verbosity parameter

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 27/06/16 13:16, akash.goel@intel.com wrote:
> From: Sagar Arun Kamble <sagar.a.kamble@intel.com>
>
> GuC Log buffer allocation was tied up with verbosity level kernel parameter
> i915.guc_log_level. User could be given a provision to enable logging at
> runtime and not necessarily during load time only. This patch will perform
> allocation of shared log buffer always but will initially enable logging on
> GuC side through init params based on i915.guc_log_level.
>
> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
> Signed-off-by: Akash Goel <akash.goel@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 3 ---
>   drivers/gpu/drm/i915/intel_guc_loader.c    | 8 +++++---
>   2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 355b647..28a810f 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -826,9 +826,6 @@ static void guc_create_log(struct intel_guc *guc)
>   	unsigned long offset;
>   	uint32_t size, flags;
>
> -	if (i915.guc_log_level < GUC_LOG_VERBOSITY_MIN)
> -		return;
> -
>   	if (i915.guc_log_level > GUC_LOG_VERBOSITY_MAX)
>   		i915.guc_log_level = GUC_LOG_VERBOSITY_MAX;
>
> diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
> index 8fe96a2..db3c897 100644
> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
> @@ -173,11 +173,13 @@ static void set_guc_init_params(struct drm_i915_private *dev_priv)
>   	params[GUC_CTL_FEATURE] |= GUC_CTL_DISABLE_SCHEDULER |
>   			GUC_CTL_VCS2_ENABLED;
>
> -	if (i915.guc_log_level >= 0) {
> -		params[GUC_CTL_LOG_PARAMS] = guc->log_flags;
> +	params[GUC_CTL_LOG_PARAMS] = guc->log_flags;
> +
> +	if (i915.guc_log_level >= 0)
>   		params[GUC_CTL_DEBUG] =
>   			i915.guc_log_level << GUC_LOG_VERBOSITY_SHIFT;
> -	}
> +	else
> +		params[GUC_CTL_DEBUG] = GUC_LOG_DISABLED;
>
>   	if (guc->ads_obj) {
>   		u32 ads = (u32)i915_gem_obj_ggtt_offset(guc->ads_obj)
>

I did not manage to understand what is the benefit of always allocating 
the log buffer? If the user never enables logging it just wasted 11 
pages of memory, correct?

Looking at the later patches in the series, could you instead create the 
log buffer when logging is enabled via debugfs or implicitly via the 
relayfs access?

Or is the problem then that you would then have to reset the GuC to 
activate it?

Regards,

Tvrtko
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