[Intel-gfx] [PATCH 10/13] drm/i915: fix the CFB size check

[Maarten Lankhorst]

Op 11-11-15 om 14:39 schreef Zanoni, Paulo R:
> Em Ter, 2015-11-10 às 14:04 +0100, Maarten Lankhorst escreveu:
>> Op 10-11-15 om 13:20 schreef Zanoni, Paulo R:
>>> Em Ter, 2015-11-10 às 11:22 +0100, Maarten Lankhorst escreveu:
>>>> Op 04-11-15 om 20:10 schreef Paulo Zanoni:
>>>>> In function find_compression_threshold() we try to over-
>>>>> allocate
>>>>> CFB
>>>>> space in order to reudce reallocations and fragmentation, and
>>>>> we're
>>>>> not considering that at the CFB size check. Consider it.
>>>>>
>>>>> There is also a longer-term plan to kill
>>>>> dev_priv->fbc.uncompressed_size, but this will come later.
>>>>>
>>>>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
>>>>> ---
>>>>>  drivers/gpu/drm/i915/intel_fbc.c | 3 ++-
>>>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_fbc.c
>>>>> b/drivers/gpu/drm/i915/intel_fbc.c
>>>>> index dee99c9..e99aacc 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_fbc.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_fbc.c
>>>>> @@ -719,7 +719,8 @@ static int intel_fbc_setup_cfb(struct
>>>>> intel_crtc *crtc)
>>>>>  	size = intel_fbc_calculate_cfb_size(crtc);
>>>>>  	cpp = drm_format_plane_cpp(fb->pixel_format, 0);
>>>>>  
>>>>> -	if (size <= dev_priv->fbc.uncompressed_size)
>>>>> +	if (dev_priv->fbc.compressed_fb.allocated &&
>>>>> +	    size <= dev_priv->fbc.compressed_fb.size *
>>>>> dev_priv-
>>>>>> fbc.threshold)
>>>>>  		return 0;
>>>>>  
>>>>>  	/* Release any current block */
>>>> Should i8xx_fbc_enable be changed too then?
>>> As far as I understand, no. We're just reserving a bigger buffer in
>>> case we need it later, but the size used by the hardware is still
>>> the
>>> same. But I'm not 100% sure the i8xx code is actually correct since
>>> I
>>> didn't dig deep into the ancient scrolls. By not touching i8xx
>>> we're
>>> also avoiding a possible new regression.
>>>
>> The original check was for size <= uncompressed_size,
>> new is threshold * compressed.
> But threshold is always 1 for i8xx, so the difference of
> uncompressed_size vs compressed_fb.size is really just the
> overallocation, and the hardware doesn't even need to know we're
> overallocating.
Ah ok, wasn't aware of threshold being 1. :) In that case I guess nothing changes so patch should be safe to apply.

~Maarten