[PATCH] drm/amdgpu: set DRIVER_ATOMIC flag early

[Alex Deucher]

On Wed, Jan 24, 2018 at 1:40 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
> On Wed, Jan 24, 2018 at 9:53 AM, Harry Wentland <harry.wentland at amd.com> wrote:
>> On 2018-01-23 05:10 PM, Alex Deucher wrote:
>>> The atomic debugfs stuff gets created in drm_dev_alloc()
>>> but this gets called before we've enumerated all of our
>>> IPs, so move the DRIVER_ATOMIC flag setting to fix that.
>>>
>>> Since DRIVER_ATOMIC is a driver flag it's currently global
>>> to the driver so setting it affects all GPUs driven by the
>>> driver.  Unfortunately, not all GPUs support atomic.  Warn
>>> the user if that is the case.
>>>
>>> This is the same as our current behavior, but at least the
>>> atomic debugfs stuff gets created now.
>>>
>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>> ---
>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c           | 12 ++++++++++++
>>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  2 --
>>>  2 files changed, 12 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> index d1a695864793..367f331b4a54 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>> @@ -578,6 +578,11 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>>>       struct drm_device *dev;
>>>       unsigned long flags = ent->driver_data;
>>>       int ret, retry = 0;
>>> +     bool supports_atomic = false;
>>> +
>>> +     if (!amdgpu_virtual_display &&
>>> +         amdgpu_device_asic_has_dc_support(flags & AMD_ASIC_MASK))
>>> +             supports_atomic = true;
>>>
>>>       if ((flags & AMD_EXP_HW_SUPPORT) && !amdgpu_exp_hw_support) {
>>>               DRM_INFO("This hardware requires experimental hardware support.\n"
>>> @@ -598,6 +603,13 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>>>       if (ret)
>>>               return ret;
>>>
>>> +     /* warn the user if they mix atomic and non-atomic capable GPUs */
>>> +     if ((kms_driver.driver_features & DRIVER_ATOMIC) && !supports_atomic)
>>> +             DRM_ERROR("Mixing atomic and non-atomic capable GPUs!\n");
>>
>> Would it make sense to make kms_driver non-static to deal with the DRIVER_ATOMIC flag correctly for multi-GPU?
>
> We'd need two driver structs with the only difference being the ATOMIC
> bit.  Ideally this flag would be per device rather than per driver.
>
> There are two issues here.
>
> 1. We need to set the ATOMIC bit early enough that the atomic debugfs
> stuff gets created.  We already set the flag when dc initializes
> anyway so there is no change in behavior here other than that the
> debugfs stuff gets created.  So it seems like a net benefit to at
> least set the flag early if dc is enabled.
>
> 2. Change the flag to be per device.  This is a lot more involved
> since we need to switch all the drivers.  That part is not too bad
> since most are either atomic or not.  Where is gets tricky with amdgpu
> (and possibly other drivers) is that we would need to fix up the
> ordering of debugfs init and the drm load callbacks in
> drm_dev_register() because the debugfs atomic files are added before
> the driver load callback is called.  I'm not sure how much other
> drivers depend on that current ordering.

and the driver load callback is where we determine the conditions to
enable atomic or not.

Alex

>
> Alex
>
>
>>
>> Harry
>>
>>> +     /* support atomic early so the atomic debugfs stuff gets created */
>>> +     if (supports_atomic)
>>> +             kms_driver.driver_features |= DRIVER_ATOMIC;
>>> +
>>>       dev = drm_dev_alloc(&kms_driver, &pdev->dev);
>>>       if (IS_ERR(dev))
>>>               return PTR_ERR(dev);
>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> index 63df977fc426..597302bb5f4d 100644
>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> @@ -1625,8 +1625,6 @@ static int dm_early_init(void *handle)
>>>  {
>>>       struct amdgpu_device *adev = (struct amdgpu_device *)handle;
>>>
>>> -     adev->ddev->driver->driver_features |= DRIVER_ATOMIC;
>>> -
>>>       switch (adev->asic_type) {
>>>       case CHIP_BONAIRE:
>>>       case CHIP_HAWAII:
>>>