[Nouveau] [PATCH] drm/nouveau/fifo: Reinstate the correct engine bit programming

[Karol Herbst]

Reviewed-by: Karol Herbst <kherbst at redhat.com>

I haven't checked if other places need fixing up yet, and I still want
to test this patch, but I won't get to it until Monday. But if
everything is in place we can get this pushed next week so we can
finally fix this annoying issue :) I was also seeing some minor
graphical corruptions which would be cool if this patch fixes it as
well.

Thanks for the patch and poking us about the bug again.

On Thu, Oct 7, 2021 at 11:41 PM Marek Vasut <marex at denx.de> wrote:
>
> Commit 64f7c698bea9 ("drm/nouveau/fifo: add engine_id hook") replaced
> fifo/chang84.c g84_fifo_chan_engine() call with an indirect call of
> fifo/g84.c g84_fifo_engine_id(). The G84_FIFO_ENGN_* values returned
> from the later g84_fifo_engine_id() are incremented by 1 compared to
> the previous g84_fifo_chan_engine() return values.
>
> This is fine either way for most of the code, except this one line
> where an engine bit programmed into the hardware is derived from the
> return value. Decrement the return value accordingly, otherwise the
> wrong engine bit is programmed into the hardware and that leads to
> the following failure:
> nouveau 0000:01:00.0: gr: 00000030 [ILLEGAL_MTHD ILLEGAL_CLASS] ch 1 [003fbce000 DRM] subc 3 class 0000 mthd 085c data 00000420
>
> On the following hardware:
> lspci -s 01:00.0
> 01:00.0 VGA compatible controller: NVIDIA Corporation GT216GLM [Quadro FX 880M] (rev a2)
> lspci -ns 01:00.0
> 01:00.0 0300: 10de:0a3c (rev a2)
>
> Fixes: 64f7c698bea9 ("drm/nouveau/fifo: add engine_id hook")
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: <stable at vger.kernel.org> # 5.12+
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c
> index 353b77d9b3dc..3492c561f2cf 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/chang84.c
> @@ -82,7 +82,7 @@ g84_fifo_chan_engine_fini(struct nvkm_fifo_chan *base,
>         if (offset < 0)
>                 return 0;
>
> -       engn = fifo->base.func->engine_id(&fifo->base, engine);
> +       engn = fifo->base.func->engine_id(&fifo->base, engine) - 1;
>         save = nvkm_mask(device, 0x002520, 0x0000003f, 1 << engn);
>         nvkm_wr32(device, 0x0032fc, chan->base.inst->addr >> 12);
>         done = nvkm_msec(device, 2000,
> --
> 2.33.0
>