[Intel-gfx] [PATCH] drm/i915: Transform whitelisting WAs into a simple reg write

[Oscar Mateo]

On 10/04/2017 06:17 AM, Chris Wilson wrote:
> Quoting Mika Kuoppala (2017-10-04 13:39:13)
>> Oscar Mateo <oscar.mateo at intel.com> writes:
>>
>>> RING_FORCE_TO_NONPRIV registers do not live in the logical context. They are simply
>>> global privileged MMIO registers that happen to be powercontext saved and restored
>>> (meaning only they can survive RC6). Therefore, there is absolutely no need to save
>>> them so that they can be restored everytime we create a new logical context.
>>>
>>> Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
>>> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>>> ---
>>>   drivers/gpu/drm/i915/intel_engine_cs.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
>>> index a28e2a8..a75f5e8 100644
>>> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
>>> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
>>> @@ -845,8 +845,8 @@ static int wa_ring_whitelist_reg(struct intel_engine_cs *engine,
>>>        if (WARN_ON(index >= RING_MAX_NONPRIV_SLOTS))
>>>                return -EINVAL;
>>>   
>>> -     WA_WRITE(RING_FORCE_TO_NONPRIV(engine->mmio_base, index),
>>> -              i915_mmio_reg_offset(reg));
>>> +     I915_WRITE(RING_FORCE_TO_NONPRIV(engine->mmio_base, index),
>>> +                i915_mmio_reg_offset(reg));
>> #define WA_WRITE should also been removed as it is clearly
>> dangerous. Chris pointed out that anything with nonmasked access
>> is not part of context image, and this seems to hold true in
>> atleast with current cases.
>>
>> But removing of define can be a followup.
> I've picked up this patch and I'll squash in the -WA_WRITE into the
> removal of WA_SET_BIT and push all 3 patches at once (when the shards
> report back).
>
> Thanks for the patch, review, testing, debate and keep having fun.
> -Chris

We can also remove RING_MAX_NONPRIV_SLOTS from here:

#define I915_MAX_WA_REGS (16 + RING_MAX_NONPRIV_SLOTS)