[PATCH 1/2] drm/nouveau/bar/gf100: fix hang when calling ->fini() before ->init()
guillaume.tucker at collabora.com
Wed Dec 6 09:22:04 UTC 2017
On 05/12/17 18:32, Ben Skeggs wrote:
> On Wed, Dec 6, 2017 at 12:30 AM, Jon Hunter <jonathanh at nvidia.com> wrote:
>> On 04/12/17 18:37, Guillaume Tucker wrote:
>>> If the firmware fails to load then ->fini() will be called before the
>>> device has been initialised, causing the kernel to hang while trying
>>> to write to a register. Add a test in ->fini() to avoid this issue.
>>> This fixes a kernel hang on tegra124.
>>> Fixes: b17de35a2ebbe ("drm/nouveau/bar: implement bar1 teardown")
>>> Signed-off-by: Guillaume Tucker <guillaume.tucker at collabora.com>
>>> CC: Ben Skeggs <bskeggs at redhat.com>
>>> drivers/gpu/drm/nouveau/nvkm/subdev/bar/gf100.c | 7 +++++--
>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bar/gf100.c
>>> index a3ba7f50198b..95e2aba64aad 100644
>>> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bar/gf100.c
>>> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bar/gf100.c
>>> @@ -43,9 +43,12 @@ gf100_bar_bar1_wait(struct nvkm_bar *base)
>>> -gf100_bar_bar1_fini(struct nvkm_bar *bar)
>>> +gf100_bar_bar1_fini(struct nvkm_bar *base)
>>> - nvkm_mask(bar->subdev.device, 0x001704, 0x80000000, 0x00000000);
>>> + struct nvkm_device *device = base->subdev.device;
>>> + if (base->subdev.oneinit)
>>> + nvkm_mask(device, 0x001704, 0x80000000, 0x00000000);
>> I have tested this and it works for me. Thanks for fixing this! Would be
>> good to get Ben's ACK, but you can have my ...
> I'd love to get a good explanation as to why it hangs without this change,
> as, on the surface, it's not immediately obvious as to why it's hanging.
To be fair I'm not entirely sure either why this causes a hang, I
haven't read the TRM... The iomem has been mapped at this point,
so accessing the register should work. One clue is when you look
at _bar1_init(), the 0x1704 register is initialised with
some (device instance?) memory address. So it's possible that
the hardware does something special when you set this to 0 as in
_bar1_fini(), which may fail in particular if it was previously
not initialised with a valid address.
This is merely guesswork, would be interested to find out the
real explanation though.
>> Tested-by: Jon Hunter <jonathanh at nvidia.com>
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