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

[Jason Ekstrand]

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);
>>>
>>>
>> 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;
>>
>> 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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