1 files changed, 64 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index d1c1e0f7f262..2ca17b14b6c1 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -34,6 +34,11 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 
+enum disp_clk {
+        CDCLK,
+        CZCLK
+};
+
 struct gmbus_port {
         const char *name;
         int reg;
@@ -58,10 +63,69 @@ to_intel_gmbus(struct i2c_adapter *i2c)
         return container_of(i2c, struct intel_gmbus, adapter);
 }
 
+static int get_disp_clk_div(struct drm_i915_private *dev_priv,
+                            enum disp_clk clk)
+{
+        u32 reg_val;
+        int clk_ratio;
+
+        reg_val = I915_READ(CZCLK_CDCLK_FREQ_RATIO);
+
+        if (clk == CDCLK)
+                clk_ratio =
+                        ((reg_val & CDCLK_FREQ_MASK) >> CDCLK_FREQ_SHIFT) + 1;
+        else
+                clk_ratio = (reg_val & CZCLK_FREQ_MASK) + 1;
+
+        return clk_ratio;
+}
+
+static void gmbus_set_freq(struct drm_i915_private *dev_priv)
+{
+        int vco_freq[] = { 800, 1600, 2000, 2400 };
+        int gmbus_freq = 0, cdclk_div, hpll_freq;
+
+        BUG_ON(!IS_VALLEYVIEW(dev_priv->dev));
+
+        /* Skip setting the gmbus freq if BIOS has already programmed it */
+        if (I915_READ(GMBUSFREQ_VLV) != 0xA0)
+                return;
+
+        /* Obtain SKU information */
+        mutex_lock(&dev_priv->dpio_lock);
+        hpll_freq =
+                vlv_cck_read(dev_priv, CCK_FUSE_REG) & CCK_FUSE_HPLL_FREQ_MASK;
+        mutex_unlock(&dev_priv->dpio_lock);
+
+        /* Get the CDCLK divide ratio */
+        cdclk_div = get_disp_clk_div(dev_priv, CDCLK);
+
+        /*
+         * Program the gmbus_freq based on the cdclk frequency.
+         * BSpec erroneously claims we should aim for 4MHz, but
+         * in fact 1MHz is the correct frequency.
+         */
+        if (cdclk_div)
+                gmbus_freq = (vco_freq[hpll_freq] << 1) / cdclk_div;
+
+        if (WARN_ON(gmbus_freq == 0))
+                return;
+
+        I915_WRITE(GMBUSFREQ_VLV, gmbus_freq);
+}
+
 void
 intel_i2c_reset(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
+
+        /*
+         * In BIOS-less system, program the correct gmbus frequency
+         * before reading edid.
+         */
+        if (IS_VALLEYVIEW(dev))
+                gmbus_set_freq(dev_priv);
+
         I915_WRITE(dev_priv->gpio_mmio_base + GMBUS0, 0);
         I915_WRITE(dev_priv->gpio_mmio_base + GMBUS4, 0);
 }