drm/i915/bxt: Broxton decoupled MMIO

Decoupled MMIO is an alternative way to access forcewake domain
registers, which requires less cycles for a single read/write and
avoids frequent software forcewake.
This certainly gives advantage over the forcewake as this new
mechanism “decouples” CPU cycles and allow them to complete even
when GT is in a CPD (frequency change) or C6 state.

This can co-exist with forcewake and we will continue to use forcewake
as appropriate. E.g. 64-bit register writes to avoid writing 2 dwords
separately and land into funny situations.

v2:
- Moved platform check out of the function and got rid of duplicate
 functions to find out decoupled power domain (Chris)
- Added a check for forcewake already held and skipped decoupled
 access (Chris)
- Skipped writing 64 bit registers through decoupled MMIO (Chris)

v3:
- Improved commit message with more info on decoupled mmio (Tvrtko)
- Changed decoupled operation to enum and used u32 instead of
 uint_32 data type for register offset (Tvrtko)
- Moved HAS_DECOUPLED_MMIO to device info (Tvrtko)
- Added lookup table for converting fw_engine to pd_engine (Tvrtko)
- Improved __gen9_decoupled_read and __gen9_decoupled_write
 routines (Tvrtko)

v4:
- Fixed alignment and variable names (Chris)
- Write GEN9_DECOUPLED_REG0_DW1 register in just one go (Zhe Wang)

v5:
- Changed HAS_DECOUPLED_MMIO() argument name to dev_priv (Tvrtko)
- Sanitize info->had_decoupled_mmio at init (Chris)

Signed-off-by: Zhe Wang <zhe1.wang@intel.com>
Signed-off-by: Praveen Paneri <praveen.paneri@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479230360-22395-1-git-send-email-praveen.paneri@intel.com

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 12f004e5d71f..21b2be8981e3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -554,6 +554,18 @@ enum forcewake_domains {
 #define FW_REG_READ  (1)
 #define FW_REG_WRITE (2)
 
+enum decoupled_power_domain {
+	GEN9_DECOUPLED_PD_BLITTER = 0,
+	GEN9_DECOUPLED_PD_RENDER,
+	GEN9_DECOUPLED_PD_MEDIA,
+	GEN9_DECOUPLED_PD_ALL
+};
+
+enum decoupled_ops {
+	GEN9_DECOUPLED_OP_WRITE = 0,
+	GEN9_DECOUPLED_OP_READ
+};
+
 enum forcewake_domains
 intel_uncore_forcewake_for_reg(struct drm_i915_private *dev_priv,
 			       i915_reg_t reg, unsigned int op);
@@ -688,7 +700,8 @@ struct intel_csr {
 	func(cursor_needs_physical); \
 	func(hws_needs_physical); \
 	func(overlay_needs_physical); \
-	func(supports_tv)
+	func(supports_tv); \
+	func(has_decoupled_mmio)
 
 struct sseu_dev_info {
 	u8 slice_mask;
@@ -2650,6 +2663,8 @@ struct drm_i915_cmd_table {
 #define GT_FREQUENCY_MULTIPLIER 50
 #define GEN9_FREQ_SCALER 3
 
+#define HAS_DECOUPLED_MMIO(dev_priv) (INTEL_INFO(dev_priv)->has_decoupled_mmio)
+
 #include "i915_trace.h"
 
 static inline bool intel_scanout_needs_vtd_wa(struct drm_i915_private *dev_priv)