[Intel-gfx] [PATCH v3 1/2] drm/i915/gmbus: Increase the Bytes per Rd/Wr Op

[Ramalingam C]

>From Gen9 onwards Bspec says HW supports Max Bytes per single RD/WR op is
511Bytes instead of previous 256Bytes used in SW.

This change allows the max bytes per op upto 511Bytes from Gen9 onwards.

v2:
  No Change.
v3:
  Inline function for max_xfer_size and renaming of the macro.[Jani]

Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h  |  1 +
 drivers/gpu/drm/i915/intel_i2c.c | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 475cac07d3e6..be6114a0e8ab 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3013,6 +3013,7 @@ enum i915_power_well_id {
 #define   GMBUS_CYCLE_STOP	(4<<25)
 #define   GMBUS_BYTE_COUNT_SHIFT 16
 #define   GMBUS_BYTE_COUNT_MAX   256U
+#define   GEN9_GMBUS_BYTE_COUNT_MAX 511U
 #define   GMBUS_SLAVE_INDEX_SHIFT 8
 #define   GMBUS_SLAVE_ADDR_SHIFT 1
 #define   GMBUS_SLAVE_READ	(1<<0)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index e6875509bcd9..4367827d7661 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -361,6 +361,13 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv)
 	return ret;
 }
 
+static inline
+unsigned int gmbus_max_xfer_size(struct drm_i915_private *dev_priv)
+{
+	return (INTEL_GEN(dev_priv) >= 9) ? GEN9_GMBUS_BYTE_COUNT_MAX :
+		GMBUS_BYTE_COUNT_MAX;
+}
+
 static int
 gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv,
 		      unsigned short addr, u8 *buf, unsigned int len,
@@ -400,7 +407,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
 	int ret;
 
 	do {
-		len = min(rx_size, GMBUS_BYTE_COUNT_MAX);
+		len = min(rx_size, gmbus_max_xfer_size(dev_priv));
 
 		ret = gmbus_xfer_read_chunk(dev_priv, msg->addr,
 					    buf, len, gmbus1_index);
@@ -462,7 +469,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
 	int ret;
 
 	do {
-		len = min(tx_size, GMBUS_BYTE_COUNT_MAX);
+		len = min(tx_size, gmbus_max_xfer_size(dev_priv));
 
 		ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len,
 					     gmbus1_index);
-- 
2.7.4