Re: [PATCH] drm/i915/fbc: Apply wa_15018326506

["Govindapillai, Vinod" <vinod.govindapillai@intel.com>]

On Fri, 2025-11-07 at 07:45 -0600, Lucas De Marchi wrote:
> On Fri, Nov 07, 2025 at 01:08:15PM +0200, Jani Nikula wrote:
> > On Fri, 07 Nov 2025, "Govindapillai, Vinod"
> > <vinod.govindapillai@intel.com> wrote:
> > > On Fri, 2025-11-07 at 12:16 +0200, Jani Nikula wrote:
> > > > On Fri, 07 Nov 2025, Vinod Govindapillai
> > > > <vinod.govindapillai@intel.com> wrote:
> > > > > Disable FBC as part for the wa for the bmg variant
> > > > > 
> > > > > Bspec: 74212
> > > > > Signed-off-by: Vinod Govindapillai
> > > > > <vinod.govindapillai@intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/i915/display/intel_display_wa.c |  4 ++++
> > > > >  drivers/gpu/drm/i915/display/intel_display_wa.h |  1 +
> > > > >  drivers/gpu/drm/i915/display/intel_fbc.c        | 10
> > > > > ++++++++++
> > > > >  3 files changed, 15 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.c
> > > > > b/drivers/gpu/drm/i915/display/intel_display_wa.c
> > > > > index c528aaa679ca..ba2272d85a04 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_display_wa.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_display_wa.c
> > > > > @@ -10,6 +10,7 @@
> > > > >  #include "intel_display_core.h"
> > > > >  #include "intel_display_regs.h"
> > > > >  #include "intel_display_wa.h"
> > > > > +#include "intel_step.h"
> > > > >  
> > > > >  static void gen11_display_wa_apply(struct intel_display
> > > > > *display)
> > > > >  {
> > > > > @@ -69,6 +70,9 @@ bool __intel_display_wa(struct
> > > > > intel_display
> > > > > *display, enum intel_display_wa wa,
> > > > >  		return DISPLAY_VER(display) == 13;
> > > > >  	case INTEL_DISPLAY_WA_22014263786:
> > > > >  		return IS_DISPLAY_VERx100(display, 1100,
> > > > > 1400);
> > > > > +	case INTEL_DISPLAY_WA_15018326506:
> > > > > +		return DISPLAY_VERx100(display) == 1401 &&
> > > > > +		       INTEL_DISPLAY_STEP(display) ==
> > > > > STEP_C0;
> > > > 
> > > > IS_DISPLAY_VERx100_STEP().
> > > 
> > > I was looking into the comments for that macro! This wa apply
> > > only for
> > > step c0 (as of now)! I wasn't sure what the "until" part could be
> > > in
> > > that macro! So what do you suggest for the "until"  STEP_D0 or
> > > STEP_FOREVER in such cases!
> > 
> > If it's C0 only, then C1 is the next step, not D0.
> 
> it would be very weird to be C0 **only**, so I went to check the WA
> db
> and I don't really see any stepping restriction
> 
> Lucas De Marchi

wa_16023588340 disabled FBC in g31. But this wa 15018326506 recommends
disabling FBC for g31 which has display stepping C0 from bspec 68090.

BR
vinod

> 
> > 
> > Basically there's only one user of INTEL_DISPLAY_STEP() outside of
> > the
> > macros themselves, and we should avoid adding more users.
> > 
> > BR,
> > Jani.
> > 
> > 
> > 
> > > 
> > > BR
> > > Vinod
> > > 
> > > 
> > > > 
> > > > >  	default:
> > > > >  		drm_WARN(display->drm, 1, "Missing Wa
> > > > > number:
> > > > > %s\n", name);
> > > > >  		break;
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.h
> > > > > b/drivers/gpu/drm/i915/display/intel_display_wa.h
> > > > > index 3644e8e2b724..f648b00cb97d 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_display_wa.h
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_display_wa.h
> > > > > @@ -26,6 +26,7 @@ enum intel_display_wa {
> > > > >  	INTEL_DISPLAY_WA_16025573575,
> > > > >  	INTEL_DISPLAY_WA_14011503117,
> > > > >  	INTEL_DISPLAY_WA_22014263786,
> > > > > +	INTEL_DISPLAY_WA_15018326506,
> > > > >  };
> > > > >  
> > > > >  bool __intel_display_wa(struct intel_display *display, enum
> > > > > intel_display_wa wa, const char *name);
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c
> > > > > b/drivers/gpu/drm/i915/display/intel_fbc.c
> > > > > index a1e3083022ee..16cd99db2978 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> > > > > @@ -1521,6 +1521,16 @@ static int
> > > > > intel_fbc_check_plane(struct
> > > > > intel_atomic_state *state,
> > > > >  		return 0;
> > > > >  	}
> > > > >  
> > > > > +	/*
> > > > > +	 * wa_15018326506:
> > > > > +	 * Fixes: Underrun during media decode
> > > > > +	 * Workaround: Do not enable FBC
> > > > > +	 */
> > > > > +	if (intel_display_wa(display, 15018326506)) {
> > > > > +		plane_state->no_fbc_reason =
> > > > > "Wa_15018326506";
> > > > > +		return 0;
> > > > > +	}
> > > > > +
> > > > >  	/* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt */
> > > > >  	if (intel_display_vtd_active(display) &&
> > > > >  	    (display->platform.skylake || display-
> > > > > > platform.broxton)) {
> > > > 
> > > 
> > 
> > -- 
> > Jani Nikula, Intel