[Intel-gfx] [PATCH 1/2] drm/i915: reorganize the unclaimed register detection code

[Paulo Zanoni]

2014-08-26 7:22 GMT-03:00 Chris Wilson <chris at chris-wilson.co.uk>:
> On Wed, Jul 16, 2014 at 05:49:29PM -0300, Paulo Zanoni wrote:
>>  static void
>> -hsw_unclaimed_reg_check(struct drm_i915_private *dev_priv, u32 reg)
>> +hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv)
>>  {
>> +     if (i915.mmio_debug)
>> +             return;
>> +
>>       if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
>> -             DRM_ERROR("Unclaimed write to %x\n", reg);
>> +             DRM_ERROR("Unclaimed register detected. Please use the i915.mmio_debug=1 to debug this problem.");
>>               __raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
>>       }
>
> What was the point here? You still add an extra read to every register
> write

Well, we previously had 2 extra reads instead of 1, so with this patch
we're in a better position :)


> and then repeat the request to enable mmio_debug ad infinitum.

Yeah, this could be avoided. OTOH, on most cases it's not gonna happen
frequently enough to annoy the user.


> And
> you still check for illegal writes in the irq handler.

That just happens on HSW, not BDW+.

>
> Just kill this code.

If we do it, we won't be checking for unclaimed registers on BDW+
without i915.mmio_debug=1.


> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre



-- 
Paulo Zanoni