[Intel-gfx] [RFC PATCH 1/6] drm/i915: Remove Gen9 WAs with no effect

[Chris Wilson]

Quoting Mika Kuoppala (2017-11-09 11:42:45)
> Oscar Mateo <oscar.mateo at intel.com> writes:
> 
> > GEN8_CONFIG0 (0xD00) is a protected by a lock (bit 31) which is set by
> > the BIOS, so there is no way we can enable the three chicken bits
> > mandated by the WA (the BIOS should be doing it instead).
> >
> > v2: Rebased
> > v3: Standalone patch
> >
> > Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h | 3 ---
> >  drivers/gpu/drm/i915/intel_pm.c | 3 ---
> >  2 files changed, 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index f0f8f60..7991d90 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -355,9 +355,6 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
> >  #define   ECOCHK_PPGTT_WT_HSW                (0x2<<3)
> >  #define   ECOCHK_PPGTT_WB_HSW                (0x3<<3)
> >  
> > -#define GEN8_CONFIG0                 _MMIO(0xD00)
> > -#define  GEN9_DEFAULT_FIXES          (1 << 3 | 1 << 2 | 1 << 1)
> > -
> >  #define GAC_ECO_BITS                 _MMIO(0x14090)
> >  #define   ECOBITS_SNB_BIT            (1<<13)
> >  #define   ECOBITS_PPGTT_CACHE64B     (3<<8)
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index e09377d..5bd49a7 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -75,9 +75,6 @@ static void gen9_init_clock_gating(struct drm_i915_private *dev_priv)
> >       I915_WRITE(CHICKEN_PAR1_1,
> >                  I915_READ(CHICKEN_PAR1_1) | SKL_EDP_PSR_FIX_RDWRAP);
> >  
> > -     I915_WRITE(GEN8_CONFIG0,
> > -                I915_READ(GEN8_CONFIG0) | GEN9_DEFAULT_FIXES);
> > -
> 
> I am pondering if we should do a verifying read for workarounds
> and chickens in general.

We are getting into the igt/tools/intel_workarounds territory. i.e. not
the regression checker, but a tool that checks that all known
workarounds are applied for the platform. The debate is whether such a
tool should be entirely independent of the kernel (carrying its own w/a
db) or if we put the entire db into the kernel. I can see arguments in
favour of both...
-Chris