Re: [PATCH] drm/i915: Check idle to active before processing CSQ

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Daniel Vetter <daniel@ffwll.ch> writes:

> On Thu, Aug 06, 2015 at 05:09:17PM +0300, Mika Kuoppala wrote:
>> If idle to active bit is set, the rest of the fields
>> in CSQ are not valid.
>> 
>> Bail out early if this is the case in order to prevent
>> rest of the loop inspecting stale values.
>> 
>> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
>
> Same questions here too, what's the impact. E.g. if you only found this by
> bspec/code inspection then it's for -next, but if it's to fix some known
> breakage then it's for -fixes + cc: stable.
>

To this and the masked write one: Both of these were found
when I was trying to find out root cause for skl hangs.

They are both for -next. Both are in the correctness
department vrt bspec and I haven't observed any other
impact.

Point taken on being more verbose.

-Mika

> Thanks, Daniel
>
>> ---
>>  drivers/gpu/drm/i915/intel_lrc.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index 99bba8e..96218bf 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -497,6 +497,9 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
>>  		status_id = I915_READ(RING_CONTEXT_STATUS_BUF(ring) +
>>  				(read_pointer % 6) * 8 + 4);
>>  
>> +		if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
>> +			continue;
>> +
>>  		if (status & GEN8_CTX_STATUS_PREEMPTED) {
>>  			if (status & GEN8_CTX_STATUS_LITE_RESTORE) {
>>  				if (execlists_check_remove_request(ring, status_id))
>> -- 
>> 2.1.4
>> 
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>
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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