[Nouveau] [PATCH 2/3] ltc/gf100: add flush/invalidate functions

[Alexandre Courbot]

On Thu, Sep 3, 2015 at 4:19 PM, Ben Skeggs <skeggsb at gmail.com> wrote:
> On 3 September 2015 at 17:13, Alexandre Courbot <gnurou at gmail.com> wrote:
>> On Thu, Sep 3, 2015 at 4:09 PM, Ben Skeggs <skeggsb at gmail.com> wrote:
>>> On 3 September 2015 at 16:42, Alexandre Courbot <acourbot at nvidia.com> wrote:
>>>> Allow clients to manually flush and invalidate L2. This will be useful
>>>> for Tegra systems for which we want to write instmem using the CPU.
>>>>
>>>> Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
>>>> ---
>>>>  drm/nouveau/include/nvkm/subdev/ltc.h |  1 +
>>>>  drm/nouveau/nvkm/subdev/ltc/gf100.c   | 36 +++++++++++++++++++++++++++++++++++
>>>>  drm/nouveau/nvkm/subdev/ltc/gk104.c   |  2 ++
>>>>  drm/nouveau/nvkm/subdev/ltc/gm107.c   |  2 ++
>>>>  drm/nouveau/nvkm/subdev/ltc/priv.h    |  2 ++
>>>>  5 files changed, 43 insertions(+)
>>>>
>>>> diff --git a/drm/nouveau/include/nvkm/subdev/ltc.h b/drm/nouveau/include/nvkm/subdev/ltc.h
>>>> index 5464fcf482f1..3d4dbbf9aab3 100644
>>>> --- a/drm/nouveau/include/nvkm/subdev/ltc.h
>>>> +++ b/drm/nouveau/include/nvkm/subdev/ltc.h
>>>> @@ -35,5 +35,6 @@ void nvkm_ltc_flush(struct nvkm_ltc *);
>>>>
>>>>  int gf100_ltc_new(struct nvkm_device *, int, struct nvkm_ltc **);
>>>>  int gk104_ltc_new(struct nvkm_device *, int, struct nvkm_ltc **);
>>>> +int gk20a_ltc_new(struct nvkm_device *, int, struct nvkm_ltc **);
>>>>  int gm107_ltc_new(struct nvkm_device *, int, struct nvkm_ltc **);
>>>>  #endif
>>>> diff --git a/drm/nouveau/nvkm/subdev/ltc/gf100.c b/drm/nouveau/nvkm/subdev/ltc/gf100.c
>>>> index 45ac765b753e..42ae77533865 100644
>>>> --- a/drm/nouveau/nvkm/subdev/ltc/gf100.c
>>>> +++ b/drm/nouveau/nvkm/subdev/ltc/gf100.c
>>>> @@ -122,6 +122,40 @@ gf100_ltc_intr(struct nvkm_ltc *ltc)
>>>>         }
>>>>  }
>>>>
>>>> +void
>>>> +gf100_ltc_invalidate(struct nvkm_ltc *ltc)
>>>> +{
>>>> +       struct nvkm_device *device = ltc->subdev.device;
>>>> +       s64 taken;
>>>> +
>>>> +       nvkm_wr32(device, 0x70004, 0x00000001);
>>>> +       if ((taken = nvkm_msec(device, 2000,
>>> I don't suppose you have access to information on more realistic
>>> timeouts?  I'd like to improve all the potential 2s timeout values
>>> across the driver in general, to avoid things hanging for a long time
>>> when the GPU craps itself :)
>>
>> The longest values I have ever seen are ~270ms (only during driver
>> initialization, and at low clock speeds), but anyway this should never
>> ever timeout. If it does, then we will have bigger issues than 2
>> second timeouts. :)
> Indeed it shouldn't, but when things get horribly messed up (as
> happens occasionally :P) it's annoying and can potentially stall the
> whole system until things are sorted out.  The patch is fine as-is, I
> was mostly wondering if NVIDIA have data on a maximum time this should
> ever take that we could use instead.

In nvgpu we do 200 retries with a delay of 5us in between, so we wait
at most for 1ms. Yeah, that sounds like a better measure than 2s. :)

Btw, when I wrote 270ms, I meant 270us.

1ms would be nice in that case. Let me test with it and resend this
patch with better values.

>
>>
>> Btw, wouldn't it be worth to restore macros like the old nvkm_wait()
>> to avoid having to write this verbose code every time we need to wait
>> on a register value?
> I'm fine doing that, the reason I didn't in the first place was that
> I'd planned on not having the constant 2s timeout everywhere (as
> already mentioned) :)

We can just add one extra argument that specifies how long we are
willing to wait. :P