drm/i915: Use GPLL ref clock to calculate GPU freqs on VLV/CHV

Extract the GPLL reference frequency from CCK and use it in the
GPU freq<->opcode conversions on VLV/CHV. This eliminates all the
assumptions we have about which divider is used for which czclk
frequency.

Note that unlike most clocks from CCK, the GPLL ref clock is a divided
down version of the CZ clock rather than the HPLL clock. CZ clock itself
is a divided down version of the HPLL clock though, so in effect it just
gets divided down twice.

While at it, throw in a few comments explaining the remaining constants
for anyone who later wants to compare this to the spreadsheets.

v2: Add slow/fast notes for CHV clocks (Imre)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457120584-26080-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com> (v1)

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 30fea341ae66..17603ada78ea 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -796,6 +796,7 @@ enum skl_disp_power_wells {
 #define  DSI_PLL_M1_DIV_SHIFT			0
 #define  DSI_PLL_M1_DIV_MASK			(0x1ff << 0)
 #define CCK_CZ_CLOCK_CONTROL			0x62
+#define CCK_GPLL_CLOCK_CONTROL			0x67
 #define CCK_DISPLAY_CLOCK_CONTROL		0x6b
 #define CCK_DISPLAY_REF_CLOCK_CONTROL		0x6c
 #define  CCK_TRUNK_FORCE_ON			(1 << 17)