[Intel-gfx] [PATCH 01/11] drm/i915: Don't factor in pixel multplier when deriving dotclock from link clock and M/N values

[ville . syrjala]

From: Ville Syrjälä <ville.syrj...@linux.intel.com>

We feed the non-multiplied clock to intel_link_compute_m_n(), so the
opposite operation should use the same order of operations. So we just
multiply by pixel_multiplier in the end now.

Reviewed-by: Jani Nikula <jani.nik...@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index d88057e..b45c6e6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7340,20 +7340,18 @@ static void ironlake_crtc_clock_get(struct intel_crtc 
*crtc,
        struct drm_device *dev = crtc->base.dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        enum transcoder cpu_transcoder = pipe_config->cpu_transcoder;
-       int link_freq, repeat;
+       int link_freq;
        u64 clock;
        u32 link_m, link_n;
 
-       repeat = pipe_config->pixel_multiplier;
-
        /*
         * The calculation for the data clock is:
-        * pixel_clock = ((m/n)*(link_clock * nr_lanes * repeat))/bpp
+        * pixel_clock = ((m/n)*(link_clock * nr_lanes))/bpp
         * But we want to avoid losing precison if possible, so:
-        * pixel_clock = ((m * link_clock * nr_lanes * repeat)/(n*bpp))
+        * pixel_clock = ((m * link_clock * nr_lanes)/(n*bpp))
         *
         * and the link clock is simpler:
-        * link_clock = (m * link_clock * repeat) / n
+        * link_clock = (m * link_clock) / n
         */
 
        /*
@@ -7375,10 +7373,11 @@ static void ironlake_crtc_clock_get(struct intel_crtc 
*crtc,
        if (!link_m || !link_n)
                return;
 
-       clock = ((u64)link_m * (u64)link_freq * (u64)repeat);
+       clock = ((u64)link_m * (u64)link_freq);
        do_div(clock, link_n);
 
-       pipe_config->adjusted_mode.clock = clock;
+       pipe_config->adjusted_mode.clock = clock *
+               pipe_config->pixel_multiplier;
 }
 
 /** Returns the currently programmed mode of the given pipe. */
-- 
1.8.1.5

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