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

Jani Nikula
2014-09-26T12:56:16Z

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.

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