[Intel-gfx] [PATCH 19/21] drm/i915: Move the get/put irq locking into the caller

[Tvrtko Ursulin]

On 08/06/16 11:01, Chris Wilson wrote:
> On Tue, Jun 07, 2016 at 01:46:53PM +0100, Tvrtko Ursulin wrote:
>>
>> On 03/06/16 17:08, Chris Wilson wrote:
>>> With only a single callsite for intel_engine_cs->irq_get and ->irq_put,
>>> we can reduce the code size by moving the common preamble into the
>>> caller, and we can also eliminate the reference counting.
>>>
>>> For completeness, as we are no longer doing reference counting on irq,
>>> rename the get/put vfunctions to enable/disable respectively.
>>>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> ---
>>>   drivers/gpu/drm/i915/i915_irq.c          |   8 +-
>>>   drivers/gpu/drm/i915/intel_breadcrumbs.c |  10 +-
>>>   drivers/gpu/drm/i915/intel_lrc.c         |  34 +---
>>>   drivers/gpu/drm/i915/intel_ringbuffer.c  | 269 ++++++++++---------------------
>>>   drivers/gpu/drm/i915/intel_ringbuffer.h  |   5 +-
>>>   5 files changed, 108 insertions(+), 218 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
>>> index 14b3d65bb604..5bdb433dde8c 100644
>>> --- a/drivers/gpu/drm/i915/i915_irq.c
>>> +++ b/drivers/gpu/drm/i915/i915_irq.c
>>> @@ -259,12 +259,12 @@ static void ilk_update_gt_irq(struct drm_i915_private *dev_priv,
>>>   	dev_priv->gt_irq_mask &= ~interrupt_mask;
>>>   	dev_priv->gt_irq_mask |= (~enabled_irq_mask & interrupt_mask);
>>>   	I915_WRITE(GTIMR, dev_priv->gt_irq_mask);
>>> -	POSTING_READ(GTIMR);
>>>   }
>>>
>>>   void gen5_enable_gt_irq(struct drm_i915_private *dev_priv, uint32_t mask)
>>>   {
>>>   	ilk_update_gt_irq(dev_priv, mask, mask);
>>> +	POSTING_READ_FW(GTIMR);
>>>   }
>>
>> Unrelated hunks?
>>
>> How is POSTING_READ_FW correct?
>
> The requirement here is an uncached read of the mmio register in order
> to flush the previous write to hw. A grander scheme would be to convert
> all posting reads, but that requires double checking to see if anyone
> has been cheating!

So what prevents to force-wake for getting released between the 
I915_WRITE and POSTING_READ_FW ?

Regards,

Tvrtko