Re: [PATCH 4/5] drm/i915: Let number of workarounds more clear

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

Jani Nikula <jani.nikula@linux.intel.com> writes:

> On Fri, 26 Sep 2014, Mika Kuoppala <mika.kuoppala@linux.intel.com> wrote:
>> Rodrigo Vivi <rodrigo.vivi@intel.com> writes:
>>
>>> This helps when including or removing cs workarounds.
>>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/intel_ringbuffer.c | 16 ++++++++++++----
>>>  1 file changed, 12 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> index 7c3d17a..39fbea6 100644
>>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> @@ -694,6 +694,7 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
>>>  	int ret;
>>>  	struct drm_device *dev = ring->dev;
>>>  	struct drm_i915_private *dev_priv = dev->dev_private;
>>> +	int wa_amount;
>>>  
>>>  	/*
>>>  	 * workarounds applied in this fn are part of register state context,
>>> @@ -704,10 +705,11 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
>>>  	memset(dev_priv->intel_wa_regs, 0, sizeof(dev_priv->intel_wa_regs));
>>>  
>>>  	/*
>>> -	 * update the number of dwords required based on the
>>> -	 * actual number of workarounds applied
>>> +	 * update the number of workarounds when adding or removing was
>>> +	 * in order the have propper dwords
>>>  	 */
>>> -	ret = intel_ring_begin(ring, 24);
>>> +	wa_amount = 8;
>>> +	ret = intel_ring_begin(ring, 3 * wa_amount);
>>>  	if (ret)
>>>  		return ret;
>>>  
>>
>> I have a bit mixed feelings with this patch as I have tripped
>> around here myself recently.
>>
>> I think we should just drop this patch and use:
>> ret = intel_ring_begin(ring, 3 * <amount>) on the subsequent
>> patches that modify the amount.
>>
>> This way the intel_ring_begin will always be the one that
>> shows in a diff. And raises alarm if it doesnt. We don't want
>> this to be too transparent and looking too easy for the next reader.
>> As the reviewer is the only and last line of defense ensuring
>> symmetry between intel_ring_begin and amount of emits.
>
> Considering intel_ring_emit_wa() adds all the needed information to
> dev_priv->intel_wa_regs and dev_priv->num_wa_regs anyway, we could
> trivially split this into constructing dev_priv->intel_wa_regs first,
> and doing intel_ring_begin() and the intel_ring_emit()s next, and not
> worry about this again.

My RFC series of fixing the workarounds after reset/suspend does this.

-Mika

> BR,
> Jani.
>
>>
>> -Mika
>>
>>> @@ -775,6 +777,7 @@ static int chv_init_workarounds(struct intel_engine_cs *ring)
>>>  	int ret;
>>>  	struct drm_device *dev = ring->dev;
>>>  	struct drm_i915_private *dev_priv = dev->dev_private;
>>> +	int wa_amount;
>>>  
>>>  	/*
>>>  	 * workarounds applied in this fn are part of register state context,
>>> @@ -784,7 +787,12 @@ static int chv_init_workarounds(struct intel_engine_cs *ring)
>>>  	dev_priv->num_wa_regs = 0;
>>>  	memset(dev_priv->intel_wa_regs, 0, sizeof(dev_priv->intel_wa_regs));
>>>  
>>> -	ret = intel_ring_begin(ring, 12);
>>> +	/*
>>> +	 * update the number of workarounds when adding or removing was
>>> +	 * in order the have propper dwords
>>> +	 */
>>> +	wa_amount = 4;
>>> +	ret = intel_ring_begin(ring, 3 * wa_amount);
>>>  	if (ret)
>>>  		return ret;
>>>  
>>> -- 
>>> 1.9.3
>>>
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>
> -- 
> Jani Nikula, Intel Open Source Technology Center