Re: [PATCH 1/3] drm/radeon: Disable dma rings for bo moves on r6xx

[Christian König <deathsimple@xxxxxxxxxxx>]

Am 11.07.2013 21:59, schrieb Ilija Hadzic:
> Alex,
>
> Can you please share some details about the nature or symptom of the 
> "instability". One problem that I have been seeing on my end is that 
> when I use the DMA ring intensively (by intensively I mean, calling 
> the copy function every frame), combined with some 3D rendering that 
> causes a lot of cs_ioctl calls, that I can provoke a corruption of the 
> olist field in radeon_sa_bo structure, consequently causing an oops in 
> radeon_sa_bo_try_free(). I have also found that I can suppress the 
> problem if I add some padding fields at the beginnig of the 
> radeon_sa_bo structure (essentially moving the olist field down).
>
> So I speculate that the use of DMA somehow results in corrupting that 
> structure, but I have not yet done enough experiments to prove or 
> disprove that theory (so I have not spoke up yet). Also my kernel is 
> full of my own internal hacks, and I have not yet taken the time to 
> reproduce the problem with the "stock" kernel. However, after seeing 
> your patch series, I am wondering if the instability you are referring 
> to may be of the same or similar nature.

Hi Ilija,

well that's very interesting and no it's quite unlikely that this is 
cause by the DMA ring because the radeon_sa_bo structure should be 
allocated on system memory and the GPU can usually only access it if you 
map it through GART.

Is that easily reproducible for you? Is there already an open bugreport?

Thanks,
Christian.

> thanks,
>
> Ilija
>
>
> On Thu, 11 Jul 2013, alexdeucher@xxxxxxxxx wrote:
>
> > From: Alex Deucher <alexander.deucher@xxxxxxx>
> >
> > They still seem to cause instability on some r6xx parts.
> > As a follow up, we can switch to using CP DMA for bo
> > moves on r6xx as a lighter weight alternative to using
> > the 3D engine.
> >
> > A version of this patch should also go to stable kernels.
> >
> > Tested-by: J.N. <golden.fleeced@xxxxxxxxx>
> > Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> > ---
> > drivers/gpu/drm/radeon/radeon_asic.c |   12 ++++++------
> > 1 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/radeon/radeon_asic.c 
> > b/drivers/gpu/drm/radeon/radeon_asic.c
> > index 0970774..ea5c52b 100644
> > --- a/drivers/gpu/drm/radeon/radeon_asic.c
> > +++ b/drivers/gpu/drm/radeon/radeon_asic.c
> > @@ -1026,8 +1026,8 @@ static struct radeon_asic r600_asic = {
> >         .blit_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >         .dma = &r600_copy_dma,
> >         .dma_ring_index = R600_RING_TYPE_DMA_INDEX,
> > -        .copy = &r600_copy_dma,
> > -        .copy_ring_index = R600_RING_TYPE_DMA_INDEX,
> > +        .copy = &r600_copy_blit,
> > +        .copy_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >     },
> >     .surface = {
> >         .set_reg = r600_set_surface_reg,
> > @@ -1119,8 +1119,8 @@ static struct radeon_asic rv6xx_asic = {
> >         .blit_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >         .dma = &r600_copy_dma,
> >         .dma_ring_index = R600_RING_TYPE_DMA_INDEX,
> > -        .copy = &r600_copy_dma,
> > -        .copy_ring_index = R600_RING_TYPE_DMA_INDEX,
> > +        .copy = &r600_copy_blit,
> > +        .copy_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >     },
> >     .surface = {
> >         .set_reg = r600_set_surface_reg,
> > @@ -1229,8 +1229,8 @@ static struct radeon_asic rs780_asic = {
> >         .blit_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >         .dma = &r600_copy_dma,
> >         .dma_ring_index = R600_RING_TYPE_DMA_INDEX,
> > -        .copy = &r600_copy_dma,
> > -        .copy_ring_index = R600_RING_TYPE_DMA_INDEX,
> > +        .copy = &r600_copy_blit,
> > +        .copy_ring_index = RADEON_RING_TYPE_GFX_INDEX,
> >     },
> >     .surface = {
> >         .set_reg = r600_set_surface_reg,
> > --
> > 1.7.7.5
> >
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