[Intel-gfx] [PATCH 13/20] drm/i915: Augment i915 error state to include the dump of GuC log buffer

[Goel, Akash]

On 8/12/2016 9:02 PM, Chris Wilson wrote:
> On Fri, Aug 12, 2016 at 04:20:03PM +0100, Tvrtko Ursulin wrote:
>>
>> On 12/08/16 07:25, akash.goel at intel.com wrote:
>>> From: Akash Goel <akash.goel at intel.com>
>>>
>>> Added the dump of GuC log buffer to i915 error state, as the contents of
>>> GuC log buffer would also be useful to determine that why the GPU reset
>>> was triggered.
>>>
>>> Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> Signed-off-by: Akash Goel <akash.goel at intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/i915_drv.h       |  1 +
>>>  drivers/gpu/drm/i915/i915_gpu_error.c | 27 +++++++++++++++++++++++++++
>>>  2 files changed, 28 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>> index 28ffac5..4bd3790 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>> @@ -509,6 +509,7 @@ struct drm_i915_error_state {
>>>  	struct intel_overlay_error_state *overlay;
>>>  	struct intel_display_error_state *display;
>>>  	struct drm_i915_error_object *semaphore_obj;
>>> +	struct drm_i915_error_object *guc_log_obj;
>>>
>>>  	struct drm_i915_error_engine {
>>>  		int engine_id;
>>> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
>>> index eecb870..561b523 100644
>>> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
>>> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
>>> @@ -546,6 +546,21 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
>>>  		}
>>>  	}
>>>
>>> +	if ((obj = error->guc_log_obj)) {
>>> +		err_printf(m, "GuC log buffer = 0x%08x\n",
>>> +			   lower_32_bits(obj->gtt_offset));
>>> +		for (i = 0; i < obj->page_count; i++) {
>>> +			for (elt = 0; elt < PAGE_SIZE/4; elt += 4) {
>>
>> Should the condition be PAGE_SIZE / 16 ? I am not sure, looks like
>> it is counting in u32 * 4 chunks so it might be. Or I might be
>> confused..
It will be PAGE_SIZE / 4 only. It took me some iterations to get it right.
PAGE_SIZE/4 is number of dwords and
elt+=4      is covering 4 dwords in every iteration


>
> There's (or will be) a function to dump the error object in a uniform
> manner. This patch is obsolete.

There is a print_error_obj() function, but that prints one dword per line.
For GuC log buffer its better (for ease of interpretation) to print 4 
dwords per line as each sample if of 4 dwords, also headers are of 8 dwords.
Other benefit is that it reduces the line count of the error state file 
(Compared to other captured buffers like ring buffer, batch buffers, 
status page, size of Log buffer is more, 76 KB).

Best regards
Akash



> -Chris
>