From caae745a352377f48f6eb43b5040214d803a885f Mon Sep 17 00:00:00 2001 From: Benson Leung Date: Thu, 9 Feb 2012 12:03:17 -0800 Subject: [PATCH] drm/i915: Fix single msg gmbus_xfers writes gmbus_xfer with a single message (particularly a single message write) would set Bus Cycle Select to 100b, the Gen Stop cycle, instead of 101b, No Index, Stop cycle. This would not start single message i2c transactions. Also, gmbus_xfer done: will disable the interface without checking if it is idle. In the case of writes, there will be no wait on status or delay to ensure the write starts and completes before the interface is turned off. Fixed the former issue by using the same cycle selection as used in the I2C_M_RD for the write case. GMBUS_CYCLE_WAIT | (i + 1 == num ? GMBUS_CYCLE_STOP : 0) Fixed the latter by waiting on GMBUS_ACTIVE to deassert before disable. Note from the grumpy d-i-n maintainer: The first hunk that changes the gmbus read path is just cosmetics to align the code with the write path. I.e. the commit message above is slightly lying because the first issue is _only_ with writes (and not simply "particularly"). Signed-off-by: Benson Leung Reviewed-by: Daniel Kurtz Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_i2c.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 068617f..4e4ddd5 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -253,7 +253,8 @@ gmbus_xfer(struct i2c_adapter *adapter, if (msgs[i].flags & I2C_M_RD) { I915_WRITE(GMBUS1 + reg_offset, - GMBUS_CYCLE_WAIT | (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | + GMBUS_CYCLE_WAIT | + (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | (len << GMBUS_BYTE_COUNT_SHIFT) | (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_READ | GMBUS_SW_RDY); @@ -282,7 +283,8 @@ gmbus_xfer(struct i2c_adapter *adapter, I915_WRITE(GMBUS3 + reg_offset, val); I915_WRITE(GMBUS1 + reg_offset, - (i + 1 == num ? GMBUS_CYCLE_STOP : GMBUS_CYCLE_WAIT) | + GMBUS_CYCLE_WAIT | + (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | (msgs[i].len << GMBUS_BYTE_COUNT_SHIFT) | (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_WRITE | GMBUS_SW_RDY); @@ -321,9 +323,12 @@ clear_err: I915_WRITE(GMBUS1 + reg_offset, 0); done: - /* Mark the GMBUS interface as disabled. We will re-enable it at the - * start of the next xfer, till then let it sleep. + /* Mark the GMBUS interface as disabled after waiting for idle. + * We will re-enable it at the start of the next xfer, + * till then let it sleep. */ + if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, 10)) + DRM_INFO("GMBUS timed out waiting for idle\n"); I915_WRITE(GMBUS0 + reg_offset, 0); ret = i; goto out; -- 2.7.4