> -----Original Message-----
> From: Zanoni, Paulo R <paulo.r.zanoni@xxxxxxxxx>
> Sent: Tuesday, March 10, 2020 4:48 AM
> To: B S, Karthik <karthik.b.s@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: ville.syrjala@xxxxxxxxxxxxxxx; Kulkarni, Vandita
> <vandita.kulkarni@xxxxxxxxx>; Shankar, Uma <uma.shankar@xxxxxxxxx>
> Subject: Re: [RFC 2/7] drm/i915: Add support for async flips in I915
>
> Em sex, 2020-03-06 às 17:09 +0530, Karthik B S escreveu:
> > Enable support for async flips in I915.
> > Set the Async Address Update Enable bit in plane ctl when async flip
> > is requested.
> >
> > Signed-off-by: Karthik B S <karthik.b.s@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_display.c | 4 ++++
> > drivers/gpu/drm/i915/i915_reg.h | 1 +
> > 2 files changed, 5 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > b/drivers/gpu/drm/i915/display/intel_display.c
> > index dd47eb65b563..4ce9897f5c58 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -4756,6 +4756,9 @@ u32 skl_plane_ctl(const struct intel_crtc_state
> *crtc_state,
> > plane_ctl |=
> PLANE_CTL_YUV_RANGE_CORRECTION_DISABLE;
> > }
> >
> > + if (crtc_state->uapi.async_flip)
> > + plane_ctl |= PLANE_CTL_ASYNC_FLIP;
> > +
> > plane_ctl |= skl_plane_ctl_format(fb->format->format);
> > plane_ctl |= skl_plane_ctl_tiling(fb->modifier);
> > plane_ctl |= skl_plane_ctl_rotate(rotation &
> DRM_MODE_ROTATE_MASK);
> > @@ -17738,6 +17741,7 @@ static void intel_mode_config_init(struct
> > drm_i915_private *i915)
> >
> > mode_config->funcs = &intel_mode_funcs;
> >
> > + mode_config->async_page_flip = true;
>
> We should only enable the feature to user space after it has been fully
> implemented inside the Kernel. Think about the case where git-bisect
> decides to land at exactly this commit when someone is debugging a failure
> unrelated to async vblanks.
>
> Also, when features have trivial on/off switches like the line above, it's
> better if the patch that enables the feature only contains the line that toggles
> the on/off switch. This way, if a revert is needed, we can just switch it to off
> without removing more code. Also, it enables us to land the rest of the code
> while keeping the feature off for stabilization.
>
> Also, the line above is enabling the feature for every platform, which is
> probably not a goal of this series.
Agreed. Will make the on/off part a separate patch and also add a gen check for it.
>
>
> > /*
> > * Maximum framebuffer dimensions, chosen to match
> > * the maximum render engine surface size on gen4+.
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > b/drivers/gpu/drm/i915/i915_reg.h index 80cf02a6eec1..42037aee9b78
> > 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -6794,6 +6794,7 @@ enum {
> > #define PLANE_CTL_TILED_X (1 << 10)
> > #define PLANE_CTL_TILED_Y (4 << 10)
> > #define PLANE_CTL_TILED_YF (5 << 10)
> > +#define PLANE_CTL_ASYNC_FLIP (1 << 9)
> > #define PLANE_CTL_FLIP_HORIZONTAL (1 << 8)
> > #define PLANE_CTL_MEDIA_DECOMPRESSION_ENABLE (1 << 4) /*
> TGL+ */
> > #define PLANE_CTL_ALPHA_MASK (0x3 << 4) /* Pre-GLK
> */
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