From: Ben Widawsky Date: Wed, 2 Oct 2013 16:25:02 +0000 (-0700) Subject: drm/i915: Clean up the ring scaling calculations X-Git-Tag: v3.13-rc1~69^2~81^2~10 X-Git-Url: http://git.agner.ch/gitweb/?a=commitdiff_plain;h=f6aca45c060d43db083a5ae34ac6ad3bbefe81da;p=linux.git drm/i915: Clean up the ring scaling calculations 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. 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 CC: Chris Wilson Signed-off-by: Ben Widawsky Reviewed-by: Jesse Barnes Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index 698257cf6381..9753bd9591eb 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); /* * For each potential GPU frequency, load a ring frequency we'd like @@ -3678,7 +3678,7 @@ void gen6_update_ring_freq(struct drm_device *dev) unsigned int ia_freq = 0, ring_freq = 0; if (IS_HASWELL(dev)) { - ring_freq = (gpu_freq * 5 + 3) / 4; + ring_freq = mult_frac(gpu_freq, 5, 4); ring_freq = max(min_ring_freq, ring_freq); /* leave ia_freq as the default, chosen by cpufreq */ } else {