[Intel-gfx] [PATCH] drm/i915/huc: Check HuC status in dedicated function

[Chris Wilson]

Quoting Michel Thierry (2018-03-14 23:34:33)
> On 14/03/18 15:23, Michal Wajdeczko wrote:
> > On Wed, 14 Mar 2018 21:17:29 +0100, Michel Thierry 
> > <michel.thierry at intel.com> wrote:
> > 
> >> On 14/03/18 13:04, Michal Wajdeczko wrote:
> >>> We try to keep all HuC related code in dedicated file.
> >>> There is no need to peek HuC register directly during
> >>> handling getparam ioctl.
> >>>  Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> >>> Cc: Michel Thierry <michel.thierry at intel.com>
> >>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> >>> Cc: Anusha Srivatsa <anusha.srivatsa at intel.com>
> >>> ---
> >>>   drivers/gpu/drm/i915/i915_drv.c  |  6 +++---
> >>>   drivers/gpu/drm/i915/intel_huc.c | 25 +++++++++++++++++++++++++
> >>>   drivers/gpu/drm/i915/intel_huc.h |  1 +
> >>>   3 files changed, 29 insertions(+), 3 deletions(-)
> >>>  diff --git a/drivers/gpu/drm/i915/i915_drv.c 
> >>> b/drivers/gpu/drm/i915/i915_drv.c
> >>> index f03555e..a902e88 100644
> >>> --- a/drivers/gpu/drm/i915/i915_drv.c
> >>> +++ b/drivers/gpu/drm/i915/i915_drv.c
> >>> @@ -377,9 +377,9 @@ static int i915_getparam_ioctl(struct drm_device 
> >>> *dev, void *data,
> >>>           value = INTEL_INFO(dev_priv)->sseu.min_eu_in_pool;
> >>>           break;
> >>>       case I915_PARAM_HUC_STATUS:
> >>> -        intel_runtime_pm_get(dev_priv);
> >>> -        value = I915_READ(HUC_STATUS2) & HUC_FW_VERIFIED;
> >>> -        intel_runtime_pm_put(dev_priv);
> >>> +        value = intel_huc_check_status(&dev_priv->huc);
> >>> +        if (value < 0)
> >>> +            return value;
> >>>           break;
> >>>       case I915_PARAM_MMAP_GTT_VERSION:
> >>>           /* Though we've started our numbering from 1, and so class all
> >>> diff --git a/drivers/gpu/drm/i915/intel_huc.c 
> >>> b/drivers/gpu/drm/i915/intel_huc.c
> >>> index 1d6c47b..2912852 100644
> >>> --- a/drivers/gpu/drm/i915/intel_huc.c
> >>> +++ b/drivers/gpu/drm/i915/intel_huc.c
> >>> @@ -92,3 +92,28 @@ int intel_huc_auth(struct intel_huc *huc)
> >>>       DRM_ERROR("HuC: Authentication failed %d\n", ret);
> >>>       return ret;
> >>>   }
> >>> +
> >>> +/**
> >>> + * intel_huc_check_status() - check HuC status
> >>> + * @huc: intel_huc structure
> >>> + *
> >>> + * This function reads status register to verify if HuC
> >>> + * firmware was successfully loaded.
> >>> + *
> >>> + * Returns positive value if HuC firmware is loaded and verified
> >>> + * and -ENODEV if HuC is not present.
> >>
> >> Before if huc was not loaded, get_param would just return 0 and the 
> >> ioctl call would be OK.
> > 
> > There is another potential problem, as in case HuC was loaded, this
> > getparam would return specific bit from register instead of predefined
> > value that shall indicate "loaded/verified" like "1".
> > What if this bit from register will be moved on future platforms?
> 
> Really? ;)
> I once heard someone claiming he had talked with the hw team and they've 
> agreed not to randomly shuffle register specifications
> (please laugh with me).
> 
> > Should we still return this old one?
> > 
> >> Maybe there's a test somewhere that would break?
> > 
> > I hope not, and given above concern, I assume we can still modify it.
> > Is there any documentation what to expect from this getparam?
> > 
> 
> And the media driver would survive the change [1] if that's what we care 
> about.
> 
> But is the response from getparam ABI? I would say just 
> drm_i915_getparam_t is.

So long as we obey the rule to not overwrite on error, we should be
within the existing ABI. Then we only have the argument over what errno
suits the ABI.

-ENODEV is what we have been using for a user call for a function not
supported by the HW, so fine by me.

Pushed, thanks for the patch and review.
-Chris