Re: [RFC 1/4] drm/i915/uc: Add ops to intel_uc

[Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>]

On 12/12/19 1:53 PM, Michal Wajdeczko wrote:
> On Thu, 12 Dec 2019 01:23:33 +0100, Daniele Ceraolo Spurio 
> <daniele.ceraolospurio@xxxxxxxxx> wrote:
>
> > On 12/10/19 12:47 PM, Michal Wajdeczko wrote:
> > > Instead of spreading multiple conditionals across the uC code
> > > to find out current mode of uC operation, start using predefined
> > > set of function pointers that reflect that mode.
> > >  Begin with pair of init_hw/fini_hw functions that are responsible
> > > for uC hardware initialization and cleanup.
> > >  Signed-off-by: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
> > > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
> > > ---
> > >   drivers/gpu/drm/i915/gt/uc/intel_uc.c | 49 +++++++++++++++++++++++----
> > >   drivers/gpu/drm/i915/gt/uc/intel_uc.h | 23 +++++++++++--
> > >   2 files changed, 63 insertions(+), 9 deletions(-)
> > >  diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c 
> > > b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > > index c6519066a0f6..e3d1359f9719 100644
> > > --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > > @@ -12,6 +12,10 @@
> > >     #include "i915_drv.h"
> > >   +extern const struct intel_uc_ops uc_ops_none;
> > > +extern const struct intel_uc_ops uc_ops_off;
> > > +extern const struct intel_uc_ops uc_ops_on;
> > > +
> > >   /* Reset GuC providing us with fresh state for both GuC and HuC.
> > >    */
> > >   static int __intel_uc_reset_hw(struct intel_uc *uc)
> > > @@ -89,6 +93,13 @@ void intel_uc_init_early(struct intel_uc *uc)
> > >       intel_huc_init_early(&uc->huc);
> > >         __confirm_options(uc);
> > > +
> > > +    if (intel_uc_uses_guc(uc))
> > > +        uc->ops = &uc_ops_on;
> > > +    else if (intel_uc_supports_guc(uc))
> > > +        uc->ops = &uc_ops_off;
> > > +    else
> > > +        uc->ops = &uc_ops_none;
> > >   }
> > >     void intel_uc_driver_late_release(struct intel_uc *uc)
> > > @@ -413,24 +424,36 @@ static bool uc_is_wopcm_locked(struct intel_uc 
> > > *uc)
> > >              (intel_uncore_read(uncore, DMA_GUC_WOPCM_OFFSET) & 
> > > GUC_WOPCM_OFFSET_VALID);
> > >   }
> > >   -int intel_uc_init_hw(struct intel_uc *uc)
> > > +static int __uc_check_hw(struct intel_uc *uc)
> > > +{
> > > +    GEM_BUG_ON(!intel_uc_supports_guc(uc));
> > > +
> > > +    /*
> > > +     * We can silently continue without GuC only if it was never 
> > > enabled
> > > +     * before on this system after reboot, otherwise we risk GPU hangs.
> > > +     * To check if GuC was loaded before we look at WOPCM registers.
> > > +     */
> > > +    if (uc_is_wopcm_locked(uc))
> > > +        return -EIO;
> > > +
> > > +    return 0;
> > > +}
> > > +
> > > +static int __uc_init_hw(struct intel_uc *uc)
> > >   {
> > >       struct drm_i915_private *i915 = uc_to_gt(uc)->i915;
> > >       struct intel_guc *guc = &uc->guc;
> > >       struct intel_huc *huc = &uc->huc;
> > >       int ret, attempts;
> > >   -    if (!intel_uc_supports_guc(uc))
> > > -        return 0;
> > > +    GEM_BUG_ON(!intel_uc_supports_guc(uc));
> > > +    GEM_BUG_ON(!intel_uc_uses_guc(uc));
> > >         /*
> > >        * We can silently continue without GuC only if it was never 
> > > enabled
> > >        * before on this system after reboot, otherwise we risk GPU 
> > > hangs.
> > >        * To check if GuC was loaded before we look at WOPCM registers.
> > >        */
> > > -    if (!intel_uc_uses_guc(uc) && !uc_is_wopcm_locked(uc))
> > > -        return 0;
> > > -
> > >       if (!intel_uc_fw_is_available(&guc->fw)) {
> > >           ret = uc_is_wopcm_locked(uc) ||
> > >                 intel_uc_fw_is_overridden(&guc->fw) ||
> > > @@ -528,7 +551,7 @@ int intel_uc_init_hw(struct intel_uc *uc)
> > >       return -EIO;
> > >   }
> > >   -void intel_uc_fini_hw(struct intel_uc *uc)
> > > +static void __uc_fini_hw(struct intel_uc *uc)
> > >   {
> > >       struct intel_guc *guc = &uc->guc;
> > >   @@ -628,3 +651,15 @@ int intel_uc_runtime_resume(struct intel_uc *uc)
> > >        */
> > >       return __uc_resume(uc, true);
> > >   }
> > > +
> > > +const struct intel_uc_ops uc_ops_none = {
> > > +};
> > > +
> > > +const struct intel_uc_ops uc_ops_off = {
> > > +    .init_hw = __uc_check_hw,
> > > +};
> > > +
> >
> > I'm not sold on having both uc_ops_off and uc_ops_none and I'd prefer 
> > them to be merged into one.
> > AFAICS, the only things you  do in uc_ops_off are __intel_uc_reset_hw 
> > and __uc_check_hw. __intel_uc_reset_hw shouldn't be needed, we do a GT 
> > reset when we come up and we're not touching the microcontrollers if 
> > intel_uc_uses_guc is false, so there should be no need to reset them. 
> > for __uc_check_hw, we can add an early return if 
> > !intel_uc_supports_guc so it is callable on all platforms and add it 
> > to uc_ops_none.
>
> I can drop uc_reset_hw from ops.off, but I would keep both off|none
> separate as otherwise we are blurring the idea of having dedicated
> ops without runtime checks (next step of such "merging/simplification"
> approach would be temptation to add more checks into existing ops,
> rather then preparing dedicated one). Note that we may soon add
> ops to other components and we should be consistent on usage model.

Having a dedicated set of ops just to avoid 1 runtime check seems 
overkill in the other direction to me. AFAICS We only care about the 
difference between !supported and !enabled is the init flow because the 
HW can go in a weird state if we switch from GuC enabled to disabled, so 
I doubt similar checks could proliferate since the 2 cases should be 
identical in all other paths. Or do you have a more concrete example of 
another place where the difference matters?

Daniele

> Michal
>
> > Daniele
> >
> > > +const struct intel_uc_ops uc_ops_on = {
> > > +    .init_hw = __uc_init_hw,
> > > +    .fini_hw = __uc_fini_hw,
> > > +};
> > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.h 
> > > b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
> > > index 527995c21196..36643e17a09e 100644
> > > --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.h
> > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
> > > @@ -10,7 +10,15 @@
> > >   #include "intel_huc.h"
> > >   #include "i915_params.h"
> > >   +struct intel_uc;
> > > +
> > > +struct intel_uc_ops {
> > > +    int (*init_hw)(struct intel_uc *uc);
> > > +    void (*fini_hw)(struct intel_uc *uc);
> > > +};
> > > +
> > >   struct intel_uc {
> > > +    struct intel_uc_ops const *ops;
> > >       struct intel_guc guc;
> > >       struct intel_huc huc;
> > >   @@ -25,8 +33,6 @@ void intel_uc_fetch_firmwares(struct intel_uc *uc);
> > >   void intel_uc_cleanup_firmwares(struct intel_uc *uc);
> > >   void intel_uc_sanitize(struct intel_uc *uc);
> > >   void intel_uc_init(struct intel_uc *uc);
> > > -int intel_uc_init_hw(struct intel_uc *uc);
> > > -void intel_uc_fini_hw(struct intel_uc *uc);
> > >   void intel_uc_fini(struct intel_uc *uc);
> > >   void intel_uc_reset_prepare(struct intel_uc *uc);
> > >   void intel_uc_suspend(struct intel_uc *uc);
> > > @@ -64,4 +70,17 @@ static inline bool intel_uc_uses_huc(struct 
> > > intel_uc *uc)
> > >       return intel_huc_is_enabled(&uc->huc);
> > >   }
> > >   +static inline int intel_uc_init_hw(struct intel_uc *uc)
> > > +{
> > > +    if (uc->ops->init_hw)
> > > +        return uc->ops->init_hw(uc);
> > > +    return 0;
> > > +}
> > > +
> > > +static inline void intel_uc_fini_hw(struct intel_uc *uc)
> > > +{
> > > +    if (uc->ops->fini_hw)
> > > +        uc->ops->fini_hw(uc);
> > > +}
> > > +
> > >   #endif
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