Re: [PATCH 10/15] drm/i915: Enable GuC firmware log

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

On 06/15/2015 07:36 PM, Dave Gordon wrote:
> From: Alex Dai <yu.dai@intel.com>
>
> Allocate a GEM object to hold GuC log data. A debugfs interface
> (i915_guc_log_dump) is provided to print out the log content.
>
> Issue: VIZ-4884
> Signed-off-by: Alex Dai <yu.dai@intel.com>
> Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_debugfs.c        |   29 +++++++++++++++++++
>   drivers/gpu/drm/i915/i915_guc_submission.c |   43 ++++++++++++++++++++++++++++
>   2 files changed, 72 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index c52a745..b0aa4af 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -2388,6 +2388,34 @@ static int i915_guc_load_status_info(struct seq_file *m, void *data)
>   	return 0;
>   }
>
> +static int i915_guc_log_dump(struct seq_file *m, void *data)
> +{
> +	struct drm_info_node *node = m->private;
> +	struct drm_device *dev = node->minor->dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_i915_gem_object *log_obj = dev_priv->guc.log_obj;
> +	u32 *log;
> +	int i = 0, pg;
> +
> +	if (!log_obj)
> +		return 0;
> +
> +	for (pg = 0; pg < log_obj->base.size / PAGE_SIZE; pg++) {
> +		log = kmap_atomic(i915_gem_object_get_page(log_obj, pg));
> +
> +		for (i = 0; i < PAGE_SIZE / sizeof(u32); i += 4)
> +			seq_printf(m, "0x%08x 0x%08x 0x%08x 0x%08x\n",
> +				   *(log + i), *(log + i + 1),
> +				   *(log + i + 2), *(log + i + 3));
> +
> +		kunmap_atomic(log);
> +	}

This doesn't look performance critical, but you could also use sg_miter_ 
family of functions/macros to iterate and kmap sg list pages. I did not 
bother figuring out what kind of smarts i915_gem_object_get_page does, 
but it is not likely it can beat sg_miter_ for efficiency.

Regards,

Tvrtko
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