Nouveau - Jun 2015 - [PATCH 4/5] gr/gf100: wait on bottom half of FE's pipeline

A naive question from someone who knows nothing of icmd or bundles... Would
it be better to wait for both bits to become 0 (I.e. 0x6)?
On Jun 8, 2015 11:54 AM, "Alexandre Courbot" <acourbot at
nvidia.com> wrote:
> When emitting the ICMD bundle, wait on the bottom half (bit 3 of the
> GR_STATUS register) instead of upper half (bit 2) to make sure methods
> are effectively emitted.
>
> Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
> ---
>  drm/nouveau/nvkm/engine/gr/gf100.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drm/nouveau/nvkm/engine/gr/gf100.c
> b/drm/nouveau/nvkm/engine/gr/gf100.c
> index 5606c25e5d02..01efc2c96045 100644
> --- a/drm/nouveau/nvkm/engine/gr/gf100.c
> +++ b/drm/nouveau/nvkm/engine/gr/gf100.c
> @@ -699,7 +699,7 @@ gf100_gr_icmd(struct gf100_gr_priv *priv, const struct
> gf100_gr_pack *p)
>
>                 while (addr < next) {
>                         nv_wr32(priv, 0x400200, addr);
> -                       nv_wait(priv, 0x400700, 0x00000002, 0x00000000);
> +                       nv_wait(priv, 0x400700, 0x00000004, 0x00000000);
>                         addr += init->pitch;
>                 }
>         }
> --
> 2.4.2
>
> _______________________________________________
> Nouveau mailing list
> Nouveau at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/nouveau
>
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On Mon, Jun 8, 2015 at 8:04 PM, Ilia Mirkin <imirkin at alum.mit.edu>
wrote:
> A naive question from someone who knows nothing of icmd or bundles... Would
> it be better to wait for both bits to become 0 (I.e. 0x6)?
My understanding is that a method reaching the bottom half implies it
has passed to upper half (whatever these halfs are, I need to dig into
the doc to completely figure it out), and thus that while waiting for
both bits would do no harm, it would not do any good either.

Waiting on the bottom half is what downstream does, so I think this
behavior is safe to apply to Nouveau.
>
> On Jun 8, 2015 11:54 AM, "Alexandre Courbot" <acourbot at
nvidia.com> wrote:
>>
>> When emitting the ICMD bundle, wait on the bottom half (bit 3 of the
>> GR_STATUS register) instead of upper half (bit 2) to make sure methods
>> are effectively emitted.
>>
>> Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
>> ---
>>  drm/nouveau/nvkm/engine/gr/gf100.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drm/nouveau/nvkm/engine/gr/gf100.c
>> b/drm/nouveau/nvkm/engine/gr/gf100.c
>> index 5606c25e5d02..01efc2c96045 100644
>> --- a/drm/nouveau/nvkm/engine/gr/gf100.c
>> +++ b/drm/nouveau/nvkm/engine/gr/gf100.c
>> @@ -699,7 +699,7 @@ gf100_gr_icmd(struct gf100_gr_priv *priv, const
struct
>> gf100_gr_pack *p)
>>
>>                 while (addr < next) {
>>                         nv_wr32(priv, 0x400200, addr);
>> -                       nv_wait(priv, 0x400700, 0x00000002,
0x00000000);
>> +                       nv_wait(priv, 0x400700, 0x00000004,
0x00000000);
>>                         addr += init->pitch;
>>                 }
>>         }
>> --
>> 2.4.2
>>
>> _______________________________________________
>> Nouveau mailing list
>> Nouveau at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/nouveau

On Mon, Jun 8, 2015 at 10:43 PM, Alexandre Courbot <gnurou at gmail.com>
wrote:
> On Mon, Jun 8, 2015 at 8:04 PM, Ilia Mirkin <imirkin at alum.mit.edu>
wrote:
>> A naive question from someone who knows nothing of icmd or bundles...
Would
>> it be better to wait for both bits to become 0 (I.e. 0x6)?
>
> My understanding is that a method reaching the bottom half implies it
> has passed to upper half (whatever these halfs are, I need to dig into
> the doc to completely figure it out), and thus that while waiting for
> both bits would do no harm, it would not do any good either.
>
> Waiting on the bottom half is what downstream does, so I think this
> behavior is safe to apply to Nouveau.
After checking, this seems to be correct. Upper half of the front-end
method pipeline corresponds to the decode stage, bottom half to
validate and emit. So we need to wait on the bottom half to be sure
methods are emitted.