Re: [PATCH 01/12] drm: Inline drm_color_lut_extract()

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 01/12] drm: Inline drm_color_lut_extract()
Date: Fri, 8 Nov 2019 15:36:57 +0200	[thread overview]
Message-ID: <20191108133657.GG1208@intel.com> (raw)
In-Reply-To: <20191107174014.GQ23790@phenom.ffwll.local>

On Thu, Nov 07, 2019 at 06:40:14PM +0100, Daniel Vetter wrote:
> On Thu, Nov 07, 2019 at 05:17:14PM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > This thing can get called several thousand times per LUT
> > so seems like we want to inline it to:
> > - avoid the function call overhead
> > - allow constant folding
> > 
> > A quick synthetic test (w/o any hardware interaction) with
> > a ridiculously large LUT size shows about 50% reduction in
> > runtime on my HSW and BSW boxes. Slightly less with more
> > reasonable LUT size but still easily measurable in tens
> > of microseconds.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_color_mgmt.c | 24 ------------------------
> >  include/drm/drm_color_mgmt.h     | 23 ++++++++++++++++++++++-
> 
> You forgot to add the include stanza in the kerneldoc .rst files, which
> means this is now lost from the output. Please fix.

Aye. A bit funny that we already have a bunch of other kerneldocs
in that header but it's not included in the .rst.

> -Daniel
> 
> >  2 files changed, 22 insertions(+), 25 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
> > index 4ce5c6d8de99..19c5f635992a 100644
> > --- a/drivers/gpu/drm/drm_color_mgmt.c
> > +++ b/drivers/gpu/drm/drm_color_mgmt.c
> > @@ -108,30 +108,6 @@
> >   * 	standard enum values supported by the DRM plane.
> >   */
> >  
> > -/**
> > - * drm_color_lut_extract - clamp and round LUT entries
> > - * @user_input: input value
> > - * @bit_precision: number of bits the hw LUT supports
> > - *
> > - * Extract a degamma/gamma LUT value provided by user (in the form of
> > - * &drm_color_lut entries) and round it to the precision supported by the
> > - * hardware.
> > - */
> > -uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision)
> > -{
> > -	uint32_t val = user_input;
> > -	uint32_t max = 0xffff >> (16 - bit_precision);
> > -
> > -	/* Round only if we're not using full precision. */
> > -	if (bit_precision < 16) {
> > -		val += 1UL << (16 - bit_precision - 1);
> > -		val >>= 16 - bit_precision;
> > -	}
> > -
> > -	return clamp_val(val, 0, max);
> > -}
> > -EXPORT_SYMBOL(drm_color_lut_extract);
> > -
> >  /**
> >   * drm_crtc_enable_color_mgmt - enable color management properties
> >   * @crtc: DRM CRTC
> > diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h
> > index d1c662d92ab7..069b21d61871 100644
> > --- a/include/drm/drm_color_mgmt.h
> > +++ b/include/drm/drm_color_mgmt.h
> > @@ -29,7 +29,28 @@
> >  struct drm_crtc;
> >  struct drm_plane;
> >  
> > -uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision);
> > +/**
> > + * drm_color_lut_extract - clamp and round LUT entries
> > + * @user_input: input value
> > + * @bit_precision: number of bits the hw LUT supports
> > + *
> > + * Extract a degamma/gamma LUT value provided by user (in the form of
> > + * &drm_color_lut entries) and round it to the precision supported by the
> > + * hardware.
> > + */
> > +static inline u32 drm_color_lut_extract(u32 user_input, int bit_precision)
> > +{
> > +	u32 val = user_input;
> > +	u32 max = 0xffff >> (16 - bit_precision);
> > +
> > +	/* Round only if we're not using full precision. */
> > +	if (bit_precision < 16) {
> > +		val += 1UL << (16 - bit_precision - 1);
> > +		val >>= 16 - bit_precision;
> > +	}
> > +
> > +	return clamp_val(val, 0, max);
> > +}
> >  
> >  void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
> >  				uint degamma_lut_size,
> > -- 
> > 2.23.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel
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