Re: [PATCH v2 15/17] drm/gma500: Stop using mode->private_flags

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Apr 07, 2020 at 09:35:37PM +0200, Sam Ravnborg wrote:
> On Tue, Apr 07, 2020 at 10:08:00PM +0300, Ville Syrjälä wrote:
> > On Tue, Apr 07, 2020 at 08:56:53PM +0200, Sam Ravnborg wrote:
> > > Hi Ville.
> > > 
> > > On Fri, Apr 03, 2020 at 11:40:06PM +0300, Ville Syrjala wrote:
> > > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > 
> > > > gma500 only uses mode->private_flags to convey the sdvo pixel
> > > > multiplier from the encoder .mode_fixup() hook to the encoder
> > > > .mode_set() hook. Those always seems get called as a pair so
> > > > let's just stuff the pixel multiplier into the encoder itself
> > > > as there are no state objects we could use in this non-atomic
> > > > driver.
> > > > 
> > > > Paves the way for nuking mode->private_flag.
> > > Nice little clean-up. One comment below.
> > > 
> > > 	Sam
> > > > 
> > > > Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
> > > > CC: Sam Ravnborg <sam@ravnborg.org>
> > > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > > Cc: Emil Velikov <emil.l.velikov@gmail.com>
> > > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > ---
> > > >  drivers/gpu/drm/gma500/psb_intel_drv.h  | 19 -------------------
> > > >  drivers/gpu/drm/gma500/psb_intel_sdvo.c | 11 ++++++-----
> > > >  2 files changed, 6 insertions(+), 24 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/gma500/psb_intel_drv.h b/drivers/gpu/drm/gma500/psb_intel_drv.h
> > > > index fb601983cef0..3dd5718c3e31 100644
> > > > --- a/drivers/gpu/drm/gma500/psb_intel_drv.h
> > > > +++ b/drivers/gpu/drm/gma500/psb_intel_drv.h
> > > > @@ -56,25 +56,6 @@
> > > >  #define INTEL_OUTPUT_DISPLAYPORT 9
> > > >  #define INTEL_OUTPUT_EDP 10
> > > >  
> > > > -#define INTEL_MODE_PIXEL_MULTIPLIER_SHIFT (0x0)
> > > > -#define INTEL_MODE_PIXEL_MULTIPLIER_MASK (0xf << INTEL_MODE_PIXEL_MULTIPLIER_SHIFT)
> > > > -
> > > > -static inline void
> > > > -psb_intel_mode_set_pixel_multiplier(struct drm_display_mode *mode,
> > > > -				int multiplier)
> > > > -{
> > > > -	mode->clock *= multiplier;
> > > > -	mode->private_flags |= multiplier;
> > > > -}
> > > > -
> > > > -static inline int
> > > > -psb_intel_mode_get_pixel_multiplier(const struct drm_display_mode *mode)
> > > > -{
> > > > -	return (mode->private_flags & INTEL_MODE_PIXEL_MULTIPLIER_MASK)
> > > > -	       >> INTEL_MODE_PIXEL_MULTIPLIER_SHIFT;
> > > > -}
> > > > -
> > > > -
> > > >  /*
> > > >   * Hold information useally put on the device driver privates here,
> > > >   * since it needs to be shared across multiple of devices drivers privates.
> > > > diff --git a/drivers/gpu/drm/gma500/psb_intel_sdvo.c b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > > > index 264d7ad004b4..9e88a37f55e9 100644
> > > > --- a/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > > > +++ b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > > > @@ -132,6 +132,8 @@ struct psb_intel_sdvo {
> > > >  	/* DDC bus used by this SDVO encoder */
> > > >  	uint8_t ddc_bus;
> > > >  
> > > > +	u8 pixel_multiplier;
> > > > +
> > > 
> > > There is really no good reason to use an u8 here.
> > 
> > Wastes less space.
> 
> When there is a good reason - use the size limited variants.
> But in this use case there is no reason to space optimize it.

IMO when it's stuffed into a structure there's no reason not to
optimize it. At some point it all starts to add up.

At least i915 suffers a lot from bloated structures (dev_priv
and atomic state structs being the prime examples) where we
could probably shave dozens if not hundreds of bytes if
everything just used the smallest type possible. In fact
this series does shave dozens of bytes from the crtc state
alone.

> 
> When in the slightly pedantic mode, using u8 is not consistent.
> ddc_bus defined above usese uint8_t.

u8 & co. are preferred in kernel code. Checkpatch even complains when
you use the stdint types. The uint8_t here is some old leftovers.

> 
> 	Sam
> > 
> > > psb_intel_sdvo_get_pixel_multiplier() return an int, so use an int here
> > > too.
> > > 
> > > With this fixed:
> > > Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> > > 
> > > >  	/* Input timings for adjusted_mode */
> > > >  	struct psb_intel_sdvo_dtd input_dtd;
> > > >  
> > > > @@ -958,7 +960,6 @@ static bool psb_intel_sdvo_mode_fixup(struct drm_encoder *encoder,
> > > >  				  struct drm_display_mode *adjusted_mode)
> > > >  {
> > > >  	struct psb_intel_sdvo *psb_intel_sdvo = to_psb_intel_sdvo(encoder);
> > > > -	int multiplier;
> > > >  
> > > >  	/* We need to construct preferred input timings based on our
> > > >  	 * output timings.  To do that, we have to set the output
> > > > @@ -985,8 +986,9 @@ static bool psb_intel_sdvo_mode_fixup(struct drm_encoder *encoder,
> > > >  	/* Make the CRTC code factor in the SDVO pixel multiplier.  The
> > > >  	 * SDVO device will factor out the multiplier during mode_set.
> > > >  	 */
> > > > -	multiplier = psb_intel_sdvo_get_pixel_multiplier(adjusted_mode);
> > > > -	psb_intel_mode_set_pixel_multiplier(adjusted_mode, multiplier);
> > > > +	psb_intel_sdvo->pixel_multiplier =
> > > > +		psb_intel_sdvo_get_pixel_multiplier(adjusted_mode);
> > > > +	adjusted_mode->clock *= psb_intel_sdvo->pixel_multiplier;
> > > >  
> > > >  	return true;
> > > >  }
> > > > @@ -1002,7 +1004,6 @@ static void psb_intel_sdvo_mode_set(struct drm_encoder *encoder,
> > > >  	u32 sdvox;
> > > >  	struct psb_intel_sdvo_in_out_map in_out;
> > > >  	struct psb_intel_sdvo_dtd input_dtd;
> > > > -	int pixel_multiplier = psb_intel_mode_get_pixel_multiplier(adjusted_mode);
> > > >  	int rate;
> > > >  	int need_aux = IS_MRST(dev) ? 1 : 0;
> > > >  
> > > > @@ -1060,7 +1061,7 @@ static void psb_intel_sdvo_mode_set(struct drm_encoder *encoder,
> > > >  
> > > >  	(void) psb_intel_sdvo_set_input_timing(psb_intel_sdvo, &input_dtd);
> > > >  
> > > > -	switch (pixel_multiplier) {
> > > > +	switch (psb_intel_sdvo->pixel_multiplier) {
> > > >  	default:
> > > >  	case 1: rate = SDVO_CLOCK_RATE_MULT_1X; break;
> > > >  	case 2: rate = SDVO_CLOCK_RATE_MULT_2X; break;
> > > > -- 
> > > > 2.24.1
> > > > 
> > > > _______________________________________________
> > > > dri-devel mailing list
> > > > dri-devel@lists.freedesktop.org
> > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > 
> > -- 
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel
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