[PATCH r128] Do not disable gouraud shading for a render op

[Connor Behan]

On 26/11/13 09:50 PM, Alex Deucher wrote:
> On Tue, Nov 26, 2013 at 10:36 PM, Connor Behan
> <connor.behan at gmail.com> wrote:
>> [Fixing subject line]
>>
>>
>> On 26/11/13 05:59 AM, Alex Deucher wrote:
>>> On Fri, Nov 22, 2013 at 3:25 PM, Connor Behan
>>> <connor.behan at gmail.com> wrote:
>>>> The EXA Composite hooks should not overwrite any register values
>>>> expected by DRI. Initial testing of the EXA support revealed that
>>>> R128_WINDOW_XY_OFFSET is one register where we have to be careful.
>>>> However, it was mostly tested using glxgears which does not stress the
>>>> driver very much. Going through the various 3D screensavers one by one
>>>> reveals a bug where certain models turn green if compositing is enabled.
>>>>
>>>> It seems that if we slightly alter the values passed to R128_SETUP_CNTL
>>>> and R128_PM4_VC_FPU_SETUP, the 3D driver will be happy and compositing
>>>> will still work. The proper way would be to constantly save and restore
>>>> register values but this showed poor performance when dragging 3D
>>>> windows across the screen.
>>> You could always just reset the value after each draw command as part
>>> of the command stream.  That said, if the options don't affect the
>>> drawing for EXA, it should be fine.
>>>
>> Before I go back to experimenting with this, do you have a guess about
>> whether this would degrade performance? With an xfce desktop there are
>> roughly 10 composite operations per second. Counting the arguments to
>> BEGIN_RING, it seems that each one currently requires 70 register
>> writes. At first I thought there was worse performance when saving and
>> restoring registers because of the extra 12 writes and 6 reads that
>> would be needed.
> I don't think you can read registers via the CCE.  Command processors
> are generally write only.  For my suggestion, you only need two
> additional dword writes.  Just write R128_SETUP_CNTL and
> R128_PM4_VC_FPU_SETUP after you send the draw packet (basically at the
> end of R128CCEComposite()).  Ideally you'd just reset the values of
> those registers once at the end of the indirect buffer when you submit
> it to the kernel.  It seems like maybe the 3D driver isn't programming
> these registers at all.  In general the ddx and mesa shouldn't depend
> on each other's state at all.
Thanks for the explanation. From what I can tell, mesa programs the
registers once when you open a 3D window, but after that it assumes that
nothing else will be changing the state. Reads appear to work for at
least one of them. Specifically, I use the value of
INREG(R128_WINDOW_XY_OFFSET) to shift the co-ordinates... otherwise all
pixmaps will be drawn in the wrong place.
>
>> Are old cards like the r128 slow at writing (with CCE) and reading
>> registers? Or is this mostly limited by the bus speed? And does it
>> depend on which register?
> It depends on the register.  Some registers cause a pipeline stall.  I
> expect these two registers probably do, so you want to minimize the
> times you set them.  I don't think the CCE supports reads at all.  If
> render accel works fine with your patch below, that's probably the
> best bet.
>
> Alex
>
>>>> Signed-off-by: Connor Behan <connor.behan at gmail.com>
>>>> ---
>>>>  src/r128_exa_render.c | 6 +++---
>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/src/r128_exa_render.c b/src/r128_exa_render.c
>>>> index f00536e..cb9f929 100644
>>>> --- a/src/r128_exa_render.c
>>>> +++ b/src/r128_exa_render.c
>>>> @@ -350,7 +350,7 @@ do {                                                        \
>>>>                     R128_TEX_MAP_ALPHA_IN_TEXTURE |     \
>>>>                     R128_TEX_CACHE_LINE_SIZE_4QW);      \
>>>>      OUT_RING_REG(R128_SETUP_CNTL,                      \
>>>> -                   R128_COLOR_SOLID_COLOR |            \
>>>> +                   R128_COLOR_GOURAUD |                \
>>>>                     R128_PRIM_TYPE_TRI |                \
>>>>                     R128_TEXTURE_ST_MULT_W |            \
>>>>                     R128_STARTING_VERTEX_1 |            \
>>>> @@ -358,9 +358,9 @@ do {                                                        \
>>>>                     R128_SUB_PIX_4BITS);                \
>>>>      OUT_RING_REG(R128_PM4_VC_FPU_SETUP,                        \
>>>>                     R128_FRONT_DIR_CCW |                \
>>>> -                   R128_BACKFACE_CULL |                \
>>>> +                   R128_BACKFACE_SOLID |               \
>>>>                     R128_FRONTFACE_SOLID |              \
>>>> -                   R128_FPU_COLOR_SOLID |              \
>>>> +                   R128_FPU_COLOR_GOURAUD |            \
>>>>                     R128_FPU_SUB_PIX_4BITS |            \
>>>>                     R128_FPU_MODE_3D |                  \
>>>>                     R128_TRAP_BITS_DISABLE |            \
>>>> --
>>>> 1.8.4
>>>>
>>>> _______________________________________________
>>>> xorg-driver-ati mailing list
>>>> xorg-driver-ati at lists.x.org
>>>> http://lists.x.org/mailman/listinfo/xorg-driver-ati


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