drm/i915/skl: Ring frequency table programming changes

Ring frequency table programming changes for SKL. No need for a
floor on ring frequency, as the issue of performance impact with
ring running below DDR frequency, is believed to be fixed on SKL

v2: Removed the check for avoiding ring frequency programming for BXT (Rodrigo)

Issue: VIZ-5144
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index ca82ad23e3f830ea10c2adc1950330032b3e3e93..9d98f4074eaea9e8766a8ddb629887f3f80d3482 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5021,6 +5021,7 @@ static void __gen6_update_ring_freq(struct drm_device *dev)
        int min_freq = 15;
        unsigned int gpu_freq;
        unsigned int max_ia_freq, min_ring_freq;
+       unsigned int max_gpu_freq, min_gpu_freq;
        int scaling_factor = 180;
        struct cpufreq_policy *policy;
 
@@ -5045,17 +5046,31 @@ static void __gen6_update_ring_freq(struct drm_device *dev)
        /* convert DDR frequency from units of 266.6MHz to bandwidth */
        min_ring_freq = mult_frac(min_ring_freq, 8, 3);
 
+       if (IS_SKYLAKE(dev)) {
+               /* Convert GT frequency to 50 HZ units */
+               min_gpu_freq = dev_priv->rps.min_freq / GEN9_FREQ_SCALER;
+               max_gpu_freq = dev_priv->rps.max_freq / GEN9_FREQ_SCALER;
+       } else {
+               min_gpu_freq = dev_priv->rps.min_freq;
+               max_gpu_freq = dev_priv->rps.max_freq;
+       }
+
        /*
         * For each potential GPU frequency, load a ring frequency we'd like
         * to use for memory access.  We do this by specifying the IA frequency
         * the PCU should use as a reference to determine the ring frequency.
         */
-       for (gpu_freq = dev_priv->rps.max_freq; gpu_freq >= dev_priv->rps.min_freq;
-            gpu_freq--) {
-               int diff = dev_priv->rps.max_freq - gpu_freq;
+       for (gpu_freq = max_gpu_freq; gpu_freq >= min_gpu_freq; gpu_freq--) {
+               int diff = max_gpu_freq - gpu_freq;
                unsigned int ia_freq = 0, ring_freq = 0;
 
-               if (INTEL_INFO(dev)->gen >= 8) {
+               if (IS_SKYLAKE(dev)) {
+                       /*
+                        * ring_freq = 2 * GT. ring_freq is in 100MHz units
+                        * No floor required for ring frequency on SKL.
+                        */
+                       ring_freq = gpu_freq;
+               } else if (INTEL_INFO(dev)->gen >= 8) {
                        /* max(2 * GT, DDR). NB: GT is 50MHz units */
                        ring_freq = max(min_ring_freq, gpu_freq);
                } else if (IS_HASWELL(dev)) {