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.
In fact, during experiments using the GMBUS interrupts, the HW_RDY interrupt would only trigger for transactions >4 bytes after 2 writes to GMBUS3.
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; }