> -----Original Message-----
> From: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> Sent: Thursday, April 30, 2020 12:25 AM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Gupta, Anshuman <anshuman.gupta@xxxxxxxxx>; Shankar, Uma
> <uma.shankar@xxxxxxxxx>
> Subject: [PATCH 3/3] drm/i915: Streamline the artihmetic
>
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> All these ROUNDIND_FACTORs and whatnot are making this thing hard to read. Get
Nit pick: Typo in ROUNDING
> rid of them. And let's massage some of the fractions to give us less questionable
> intermediate results and perhaps less divisions.
>
> Also looks like a good helping of 64bit math stuff is needed to avoid some of
> overflows present in the current code. There might still be a few overflows, namely
> when calculating link_clks_available/samples_room (would require a huge hblank
> though), and potentially when calculating hblank_rise (not sure how large
> link_clks_active can get).
>
> It looks like we're still not calculating exactly what the spec says since we truncate
> tu_data and tu_line early. But I'm too lazy to figure out if we could avoid that.
>
> Cc: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
> Cc: Uma Shankar <uma.shankar@xxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_audio.c | 54 ++++++++--------------
> 1 file changed, 19 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_audio.c
> b/drivers/gpu/drm/i915/display/intel_audio.c
> index 00f7a3cf9a04..05cab508c626 100644
> --- a/drivers/gpu/drm/i915/display/intel_audio.c
> +++ b/drivers/gpu/drm/i915/display/intel_audio.c
> @@ -517,16 +517,16 @@ static void hsw_audio_codec_disable(struct intel_encoder
> *encoder,
> /* Add a factor to take care of rounding and truncations */ #define
> ROUNDING_FACTOR 10000
We should drop this declaration as well, as its of no use now.
Overall this looks much better for sure, thanks Ville.
Reviewed-by: Uma Shankar <uma.shankar@xxxxxxxxx>
> -static unsigned int get_hblank_early_enable_config(struct intel_encoder *encoder,
> - const struct intel_crtc_state
> *crtc_state)
> +static unsigned int calc_hblank_early_prog(struct intel_encoder *encoder,
> + const struct intel_crtc_state *crtc_state)
> {
> struct drm_i915_private *i915 = to_i915(encoder->base.dev);
> unsigned int link_clks_available, link_clks_required;
> unsigned int tu_data, tu_line, link_clks_active;
> - unsigned int hblank_rise, hblank_early_prog;
> unsigned int h_active, h_total, hblank_delta, pixel_clk;
> unsigned int fec_coeff, cdclk, vdsc_bpp;
> unsigned int link_clk, lanes;
> + unsigned int hblank_rise;
>
> h_active = crtc_state->hw.adjusted_mode.crtc_hdisplay;
> h_total = crtc_state->hw.adjusted_mode.crtc_htotal;
> @@ -542,44 +542,33 @@ static unsigned int get_hblank_early_enable_config(struct
> intel_encoder *encoder
> "lanes = %u vdsc_bpp = %u cdclk = %u\n",
> h_active, link_clk, lanes, vdsc_bpp, cdclk);
>
> - if (WARN_ON(!link_clk || !lanes || !vdsc_bpp || !cdclk))
> + if (WARN_ON(!link_clk || !pixel_clk || !lanes || !vdsc_bpp || !cdclk))
> return 0;
>
> - link_clks_available = ((((h_total - h_active) *
> - ((link_clk * ROUNDING_FACTOR) /
> - pixel_clk)) / ROUNDING_FACTOR) - 28);
> - link_clks_required = DIV_ROUND_UP(192000, (1000 * pixel_clk / h_total)) *
> ((48 /
> - lanes) + 2);
> + link_clks_available = (h_total - h_active) * link_clk / pixel_clk - 28;
> + link_clks_required = DIV_ROUND_UP(192000 * h_total, 1000 * pixel_clk)
> +* (48 / lanes + 2);
>
> if (link_clks_available > link_clks_required)
> hblank_delta = 32;
> else
> - hblank_delta = DIV_ROUND_UP(((((5 * ROUNDING_FACTOR) /
> - link_clk) + ((5 *
> - ROUNDING_FACTOR) /
> - cdclk)) * pixel_clk),
> - ROUNDING_FACTOR);
> + hblank_delta = DIV64_U64_ROUND_UP(mul_u32_u32(5 * link_clk +
> 5 * cdclk, pixel_clk),
> + mul_u32_u32(link_clk, cdclk));
>
> - tu_data = (pixel_clk * vdsc_bpp * 8) / ((link_clk *
> - lanes * fec_coeff) / 1000000);
> - tu_line = (((h_active * link_clk * fec_coeff) /
> - 1000000) / (64 * pixel_clk));
> + tu_data = div64_u64(mul_u32_u32(pixel_clk * vdsc_bpp * 8, 1000000),
> + mul_u32_u32(link_clk * lanes, fec_coeff));
> + tu_line = div64_u64(h_active * mul_u32_u32(link_clk, fec_coeff),
> + mul_u32_u32(64 * pixel_clk, 1000000));
> link_clks_active = (tu_line - 1) * 64 + tu_data;
>
> - hblank_rise = ((link_clks_active + 6 * DIV_ROUND_UP(link_clks_active,
> - 250) + 4) * ((pixel_clk * ROUNDING_FACTOR) /
> - link_clk)) / ROUNDING_FACTOR;
> + hblank_rise = (link_clks_active + 6 * DIV_ROUND_UP(link_clks_active,
> +250) + 4) * pixel_clk / link_clk;
>
> - hblank_early_prog = h_active - hblank_rise + hblank_delta;
> -
> - return hblank_early_prog;
> + return h_active - hblank_rise + hblank_delta;
> }
>
> -static unsigned int get_sample_room_req_config(const struct intel_crtc_state
> *crtc_state)
> +static unsigned int calc_samples_room(const struct intel_crtc_state
> +*crtc_state)
> {
> unsigned int h_active, h_total, pixel_clk;
> unsigned int link_clk, lanes;
> - unsigned int samples_room;
>
> h_active = crtc_state->hw.adjusted_mode.hdisplay;
> h_total = crtc_state->hw.adjusted_mode.htotal;
> @@ -587,12 +576,8 @@ static unsigned int get_sample_room_req_config(const
> struct intel_crtc_state *cr
> link_clk = crtc_state->port_clock;
> lanes = crtc_state->lane_count;
>
> - samples_room = ((((h_total - h_active) * ((link_clk *
> - ROUNDING_FACTOR) / pixel_clk)) /
> - ROUNDING_FACTOR) - 12) / ((48 /
> - lanes) + 2);
> -
> - return samples_room;
> + return ((h_total - h_active) * link_clk - 12 * pixel_clk) /
> + (pixel_clk * (48 / lanes + 2));
> }
>
> static void enable_audio_dsc_wa(struct intel_encoder *encoder, @@ -618,8 +603,7
> @@ static void enable_audio_dsc_wa(struct intel_encoder *encoder,
> (crtc_state->hw.adjusted_mode.hdisplay >= 3840 &&
> crtc_state->hw.adjusted_mode.vdisplay >= 2160)) {
> /* Get hblank early enable value required */
> - hblank_early_prog = get_hblank_early_enable_config(encoder,
> - crtc_state);
> + hblank_early_prog = calc_hblank_early_prog(encoder, crtc_state);
> if (hblank_early_prog < 32) {
> val &= ~HBLANK_START_COUNT_MASK(pipe);
> val |= HBLANK_START_COUNT(pipe,
> HBLANK_START_COUNT_32); @@ -635,7 +619,7 @@ static void
> enable_audio_dsc_wa(struct intel_encoder *encoder,
> }
>
> /* Get samples room value required */
> - samples_room = get_sample_room_req_config(crtc_state);
> + samples_room = calc_samples_room(crtc_state);
> if (samples_room < 3) {
> val &= ~NUMBER_SAMPLES_PER_LINE_MASK(pipe);
> val |= NUMBER_SAMPLES_PER_LINE(pipe, samples_room);
> --
> 2.24.1
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