[Mesa-dev] [PATCH 27/34] i965: Make CCS stride match kernel's expectations

[Jason Ekstrand]

On Mon, Feb 27, 2017 at 5:38 PM, Jason Ekstrand <jason at jlekstrand.net>
wrote:

> On Mon, Feb 27, 2017 at 4:56 PM, Ben Widawsky <ben at bwidawsk.net> wrote:
>
>> On 17-01-31 13:24:55, Jason Ekstrand wrote:
>>
>>> On Mon, Jan 23, 2017 at 10:21 PM, Ben Widawsky <ben at bwidawsk.net> wrote:
>>>
>>> v2: Put the commit message as a comment (Topi)
>>>>
>>>> Cc: Topi Pohjolainen <topi.pohjolainen at gmail.com>
>>>> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>>> Cc: Jason Ekstrand <jason at jlekstrand.net>
>>>> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
>>>> Acked-by: Daniel Stone <daniels at collabora.com>
>>>> ---
>>>>  src/mesa/drivers/dri/i965/intel_screen.c | 5 ++++-
>>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/src/mesa/drivers/dri/i965/intel_screen.c
>>>> b/src/mesa/drivers/dri/i965/intel_screen.c
>>>> index 85070bb54d..12b3b071e4 100644
>>>> --- a/src/mesa/drivers/dri/i965/intel_screen.c
>>>> +++ b/src/mesa/drivers/dri/i965/intel_screen.c
>>>> @@ -1023,7 +1023,10 @@ intel_from_planar(__DRIimage *parent, int plane,
>>>> void *loaderPrivate)
>>>>      if (parent == NULL || parent->planar_format == NULL) {
>>>>         if (is_aux) {
>>>>            offset = parent->aux_offset;
>>>> -          stride = ALIGN(parent->pitch / 32, 128);
>>>> +          /* Make CCS stride match kernel's expectations. Mesa's
>>>> internals
>>>> +           * expect: stride = ALIGN(parent->pitch / 32, 128)
>>>> +           */
>>>> +          stride = ALIGN(parent->pitch / 64, 128);
>>>>
>>>>
I just realized that this doesn't match the picture you drew in 22/32 where
the CCS and the main color surface have the same stride.


> Does the kernel expect the alignment to be 128 or 64?  Given that ville
>>> likes 64-wide tiles, I think it should be 64.  Really, I think the more
>>> accurate calculation would be
>>>
>>> stride = ALIGN(parent->pitch, 4096) / 64;
>>>
>>
Isn't the actual CCS stride stored in parent->strides[0]?  Why are we
re-computing it from the plane 0 pitch?


> 4096 is the stride in bytes in the primary surface required to cross a
>>> single CCS tile.  The calculation you have above will work in the sense
>>> that the worst that happens is for it to align up a bit too far.  In any
>>> case, what matters is that we a) have enough space and b) exactly match
>>> the
>>> kernel's calculation.
>>>
>>> --Jason
>>>
>>>
>>>
>> This formula doesn't match the kernel's expectations (unless Ville has
>> updated
>> patches somewhere).
>>
>
> Hrm... Ok.  Having the alignment too big won't break anything, it's just a
> bit odd.
>
>
>> If you want I can do:
>> stride = ALIGN(parent->pitch, 4096) / 128;
>
>
>  That' wouldn't match either.  Let's make sure the formulas match exactly.
>
>
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