[PATCH 09/14 v5] drm/i915/intel_i2c: use double-buffered writes

Daniel Kurtz
2012-03-28T12:53:18Z

The GMBUS controller GMBUS3 register is double-buffered. Take advantage
of this by writing two 4-byte words before the first wait for HW_RDY.
This helps keep the GMBUS controller from becoming idle during long writes.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
---
drivers/gpu/drm/i915/intel_i2c.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 99a04f8..f02e52a 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -262,13 +262,6 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
POSTING_READ(GMBUS2 + reg_offset);
while (len) {
- if (wait_for(I915_READ(GMBUS2 + reg_offset) &
- (GMBUS_SATOER | GMBUS_HW_RDY),
- 50))
- return -ETIMEDOUT;
- if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
- return -ENXIO;
-
val = loop = 0;
do {
val |= *buf++ << (8 * loop);
@@ -276,6 +269,13 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,

I915_WRITE(GMBUS3 + reg_offset, val);
POSTING_READ(GMBUS2 + reg_offset);
+
+ if (wait_for(I915_READ(GMBUS2 + reg_offset) &
+ (GMBUS_SATOER | GMBUS_HW_RDY),
+ 50))
+ return -ETIMEDOUT;
+ if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+ return -ENXIO;
}
return 0;
}
--
1.7.7.3