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

[Ben Skeggs]

On 3 September 2015 at 18:02, Alexandre Courbot <gnurou at gmail.com> wrote:
> 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
Works for me :)