[Mesa-dev] [PATCH] i965/skl: Fix aligning mt->total_width to the block size

[Neil Roberts]

Ben Widawsky <ben at bwidawsk.net> writes:

> I think this is beginning to infringe upon the definition of align_w.
> The total width is a function of it's miptree properties and not the
> compressed block properties, right?
>
> In other words, if there is a case where align_w != bw, I think
> total_width should be aligned to align_w, NOT bw.

I don't think it's so clear cut. In practice the mt->total_width doesn't
really need to be aligned to anything because as far as I can tell it is
only used to calculate the row stride. The row stride is separately
aligned to whatever constraints necessary by libdrm so it doesn't really
matter what we pick here.

The reason I think that the intention was to align it to the block width
rather than the horizontal alignment is that in the non-compressed case
the total width isn't aligned to anything at all.

It's probably not worth making too much of a fuss over this patch seeing
as it doesn't make any practical difference. I'm happy to forget about
it and pretend I never noticed the inconsistency.

Regards,
- Neil

>
> (I'm not opposed to the patch, just making sure I understand.)
>
>> ---
>>  src/mesa/drivers/dri/i965/brw_tex_layout.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>> 
>> diff --git a/src/mesa/drivers/dri/i965/brw_tex_layout.c b/src/mesa/drivers/dri/i965/brw_tex_layout.c
>> index 1e7d8a1..dbb6cef 100644
>> --- a/src/mesa/drivers/dri/i965/brw_tex_layout.c
>> +++ b/src/mesa/drivers/dri/i965/brw_tex_layout.c
>> @@ -366,9 +366,8 @@ brw_miptree_layout_2d(struct intel_mipmap_tree *mt)
>>  
>>     mt->total_width = mt->physical_width0;
>>  
>> -   if (mt->compressed) {
>> -       mt->total_width = ALIGN(mt->physical_width0, mt->align_w);
>> -   }
>> +   if (mt->compressed)
>> +       mt->total_width = ALIGN(mt->total_width, bw);
>>  
>>     /* May need to adjust width to accommodate the placement of
>>      * the 2nd mipmap.  This occurs when the alignment
>> -- 
>> 1.9.3
>> 
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