On Wed, Oct 02, 2013 at 09:25:02AM -0700, Ben Widawsky wrote: > This patch attempts to clean up the ring/IA scaling programming in the > following ways. > 1. Fix the comment about the DDR frequency. The math is 266MHz, not > 133MHz. Formula was right, docs are wrong. Confirmed by inspection, units are 266MHz. > 2. Mask the DCLK register since I don't know how it is defined on future > platforms. > > 3. use mult_frac instead of magic math. > > This helps for future platform enabling. > > v2: Actually use the right patch. The v1 was a mix of things, none of > which was right. Note that due to rounding, we actually get different > values (slightly higher) for the effective ring frequency. > > v3: Use 1.25 instead of 1.33 as the original code did. (Jesse) > > CC: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> > CC: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/intel_pm.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c > index 698257c..9753bd9 100644 > --- a/drivers/gpu/drm/i915/intel_pm.c > +++ b/drivers/gpu/drm/i915/intel_pm.c > @@ -3663,9 +3663,9 @@ void gen6_update_ring_freq(struct drm_device *dev) > /* Convert from kHz to MHz */ > max_ia_freq /= 1000; > > - min_ring_freq = I915_READ(MCHBAR_MIRROR_BASE_SNB + DCLK); > - /* convert DDR frequency from units of 133.3MHz to bandwidth */ > - min_ring_freq = (2 * 4 * min_ring_freq + 2) / 3; > + min_ring_freq = I915_READ(MCHBAR_MIRROR_BASE_SNB + DCLK) & 0xf; > + /* convert DDR frequency from units of 266.6MHz to bandwidth */ > + min_ring_freq = mult_frac(min_ring_freq, 8, 3); mult_frac() does not round upwards, so that will be a potential, but small, difference. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
