[RFC][PATCH 5/5] drm/i915/display: Add Nearest-neighbor based integer scaling support
Ville Syrjälä
ville.syrjala at linux.intel.com
Fri Mar 13 19:53:01 UTC 2020
On Fri, Mar 13, 2020 at 08:45:35AM +0000, Laxminarayan Bharadiya, Pankaj wrote:
>
>
> > -----Original Message-----
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Sent: 12 March 2020 19:25
> > To: Laxminarayan Bharadiya, Pankaj
> > <pankaj.laxminarayan.bharadiya at intel.com>
> > Cc: jani.nikula at linux.intel.com; daniel at ffwll.ch; intel-
> > gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; airlied at linux.ie;
> > maarten.lankhorst at linux.intel.com; tzimmermann at suse.de;
> > mripard at kernel.org; mihail.atanassov at arm.com; Joonas Lahtinen
> > <joonas.lahtinen at linux.intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>;
> > Chris Wilson <chris at chris-wilson.co.uk>; Souza, Jose <jose.souza at intel.com>;
> > De Marchi, Lucas <lucas.demarchi at intel.com>; Roper, Matthew D
> > <matthew.d.roper at intel.com>; Deak, Imre <imre.deak at intel.com>; Shankar,
> > Uma <uma.shankar at intel.com>; linux-kernel at vger.kernel.org; Nautiyal, Ankit K
> > <ankit.k.nautiyal at intel.com>
> > Subject: Re: [RFC][PATCH 5/5] drm/i915/display: Add Nearest-neighbor based
> > integer scaling support
> >
> > On Thu, Mar 12, 2020 at 09:13:24AM +0000, Laxminarayan Bharadiya, Pankaj
> > wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > Sent: 10 March 2020 21:47
> > > > To: Laxminarayan Bharadiya, Pankaj
> > > > <pankaj.laxminarayan.bharadiya at intel.com>
> > > > Cc: jani.nikula at linux.intel.com; daniel at ffwll.ch; intel-
> > > > gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org;
> > > > airlied at linux.ie; maarten.lankhorst at linux.intel.com;
> > > > tzimmermann at suse.de; mripard at kernel.org; mihail.atanassov at arm.com;
> > > > Joonas Lahtinen <joonas.lahtinen at linux.intel.com>; Vivi, Rodrigo
> > > > <rodrigo.vivi at intel.com>; Chris Wilson <chris at chris-wilson.co.uk>;
> > > > Souza, Jose <jose.souza at intel.com>; De Marchi, Lucas
> > > > <lucas.demarchi at intel.com>; Roper, Matthew D
> > > > <matthew.d.roper at intel.com>; Deak, Imre <imre.deak at intel.com>;
> > > > Shankar, Uma <uma.shankar at intel.com>; linux- kernel at vger.kernel.org;
> > > > Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
> > > > Subject: Re: [RFC][PATCH 5/5] drm/i915/display: Add Nearest-neighbor
> > > > based integer scaling support
> > > >
> > > > On Tue, Feb 25, 2020 at 12:35:45PM +0530, Pankaj Bharadiya wrote:
> > > > > Integer scaling (IS) is a nearest-neighbor upscaling technique
> > > > > that simply scales up the existing pixels by an integer (i.e.,
> > > > > whole
> > > > > number) multiplier.Nearest-neighbor (NN) interpolation works by
> > > > > filling in the missing color values in the upscaled image with
> > > > > that of the coordinate-mapped nearest source pixel value.
> > > > >
> > > > > Both IS and NN preserve the clarity of the original image. Integer
> > > > > scaling is particularly useful for pixel art games that rely on
> > > > > sharp, blocky images to deliver their distinctive look.
> > > > >
> > > > > Program the scaler filter coefficients to enable the NN filter if
> > > > > scaling filter property is set to
> > > > > DRM_SCALING_FILTER_NEAREST_NEIGHBOR
> > > > > and enable integer scaling.
> > > > >
> > > > > Bspec: 49247
> > > > >
> > > > > Signed-off-by: Pankaj Bharadiya
> > > > > <pankaj.laxminarayan.bharadiya at intel.com>
> > > > > Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> > > > > ---
> > > > > drivers/gpu/drm/i915/display/intel_display.c | 83
> > > > > +++++++++++++++++++- drivers/gpu/drm/i915/display/intel_display.h
> > > > > +++++++++++++++++++|
> > > > > 2 + drivers/gpu/drm/i915/display/intel_sprite.c | 20 +++--
> > > > > 3 files changed, 97 insertions(+), 8 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > > > > b/drivers/gpu/drm/i915/display/intel_display.c
> > > > > index b5903ef3c5a0..6d5f59203258 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > > > > @@ -6237,6 +6237,73 @@ void skl_scaler_disable(const struct
> > > > intel_crtc_state *old_crtc_state)
> > > > > skl_detach_scaler(crtc, i);
> > > > > }
> > > > >
> > > > > +/**
> > > > > + * Theory behind setting nearest-neighbor integer scaling:
> > > > > + *
> > > > > + * 17 phase of 7 taps requires 119 coefficients in 60 dwords per set.
> > > > > + * The letter represents the filter tap (D is the center tap)
> > > > > +and the number
> > > > > + * represents the coefficient set for a phase (0-16).
> > > > > + *
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * |Index value | Data value coeffient 1 | Data value coeffient 2 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 00h | B0 | A0 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 01h | D0 | C0 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 02h | F0 | E0 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 03h | A1 | G0 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 04h | C1 | B1 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | ... | ... | ... |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 38h | B16 | A16 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 39h | D16 | C16 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 3Ah | F16 | C16 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + * | 3Bh | Reserved | G16 |
> > > > > + * +------------+------------------------+------------------------+
> > > > > + *
> > > > > + * To enable nearest-neighbor scaling: program scaler
> > > > > +coefficents with
> > > > > + * the center tap (Dxx) values set to 1 and all other values set
> > > > > +to
> > > > > +0 as per
> > > > > + * SCALER_COEFFICIENT_FORMAT
> > > > > + *
> > > > > + */
> > > > > +void skl_setup_nearest_neighbor_filter(struct drm_i915_private
> > > > *dev_priv,
> > > > > + enum pipe pipe, int scaler_id)
> > > >
> > > > skl_scaler_...
> > > >
> > > > > +{
> > > > > +
> > > > > + int coeff = 0;
> > > > > + int phase = 0;
> > > > > + int tap;
> > > > > + int val = 0;
> > > >
> > > > Needlessly wide scope for most of these.
> > > >
> > > > > +
> > > > > + /*enable the index auto increment.*/
> > > > > + intel_de_write_fw(dev_priv, SKL_PS_COEF_INDEX_SET0(pipe,
> > > > scaler_id),
> > > > > + _PS_COEE_INDEX_AUTO_INC);
> > > > > +
> > > > > + for (phase = 0; phase < 17; phase++) {
> > > > > + for (tap = 0; tap < 7; tap++) {
> > > > > + coeff++;
> > > >
> > > > Can be part of the % check.
> > >
> > > OK.
> > >
> > > >
> > > > > + if (tap == 3)
> > > > > + val = (phase % 2) ? (0x800) : (0x800 << 16);
> > > >
> > > > Parens overload.
> > >
> > > OK. Will remove.
> > > >
> > > > > +
> > > > > + if (coeff % 2 == 0) {
> > > > > + intel_de_write_fw(dev_priv,
> > > > SKL_PS_COEF_DATA_SET0(pipe, scaler_id), val);
> > > > > + val = 0;
> > > >
> > > > Can drop this val=0 if you move the variable into tight scope and
> > > > initialize there.
> > >
> > > Moving val=0 initialization to the tight scope will not work here as
> > > we need to retain "val" and write only when 2 coefficients are ready
> > > (since 2 coefficients are packed in 1 dword).
> > >
> > > e.g. for (12th , 11th) coefficients, coefficient reg value should be ( (0 << 16) |
> > 0x800).
> > > If we initialize val = 0 in tight loop, 0 will be written to coefficient register.
> >
> > Hmm, right. I guess I'd try to rearrange this to iterate the registers directly
> > instead of the phases and taps. Something like this perhaps:
> >
> > static int cnl_coef_tap(int i)
> > {
> > return i % 7;
> > }
> >
> > static u16 cnl_coef(int t)
>
> cnl_coef -> cnl_nearest_filter_coef. Right?
Right.
>
> > {
> > return t == 3 ? 0x0800 : 0x3000;
> > }
> >
> > static void cnl_program_nearest_filter_coefs(void)
> > {
> > int i;
> >
> > for (i = 0; i < 17 * 7; i += 2) {
> > uint32_t tmp;
> > int t;
> >
> > t = cnl_coef_tap(i);
> > tmp = cnl_nearest_filter_coef(t);
> >
> > t = cnl_coef_tap(i + 1);
> > tmp |= cnl_nearest_filter_coef(t) << 16;
> >
> > intel_de_write_fw(tmp);
> > }
> > }
> >
> > More readable I think. The downside being all those modulo operations but
> > hopefully that's all in the noise when it comes to performance.
>
> Looks better, thanks for spending time on this.
> I will try this out.
>
> Thanks,
> Pankaj
> >
> > --
> > Ville Syrjälä
> > Intel
--
Ville Syrjälä
Intel
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