The i915 is only able to generate a STOP cycle (i.e. finalize an i2c transaction) during a DATA or WAIT phase. In other words, the controller rejects a STOP requested as part of the first transaction in a sequence.
Thus, for the first transaction we must always use a WAIT cycle, detect when the device has finished (and is in a WAIT phase), and then either start the next transaction, or, if there are no more transactions, generate a STOP cycle.
Note: Theoretically, the last transaction of a multi-transaction sequence could initiate a STOP cycle. However, this slight optimization is left for another patch. We return -ETIMEDOUT if the hardware doesn't deactivate after the STOP cycle.
This patch also takes advantage (in the write path) of the double-buffered GMBUS3 data register by writing two 4-byte words before the first wait for HW_RDY.
Signed-off-by: Daniel Kurtz djkurtz@chromium.org --- drivers/gpu/drm/i915/intel_i2c.c | 34 +++++++++++++++++++--------------- 1 files changed, 19 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 9d5d286..7396d6e 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -212,7 +212,8 @@ gmbus_xfer(struct i2c_adapter *adapter, struct intel_gmbus, adapter); struct drm_i915_private *dev_priv = bus->dev_priv; - int i, reg_offset, ret; + int i, reg_offset; + int ret = 0;
mutex_lock(&dev_priv->gmbus_mutex);
@@ -232,7 +233,6 @@ 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) | (len << GMBUS_BYTE_COUNT_SHIFT) | (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_READ | GMBUS_SW_RDY); @@ -266,21 +266,12 @@ gmbus_xfer(struct i2c_adapter *adapter, I915_WRITE(GMBUS3 + reg_offset, val); I915_WRITE(GMBUS1 + reg_offset, 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); POSTING_READ(GMBUS2 + reg_offset);
while (len) { - if (wait_for(I915_READ(GMBUS2 + reg_offset) & - (GMBUS_SATOER | GMBUS_HW_RDY), - 50)) - goto timeout; - if (I915_READ(GMBUS2 + reg_offset) & - GMBUS_SATOER) - goto clear_err; - val = loop = 0; do { val |= *buf++ << (8 * loop); @@ -288,11 +279,18 @@ gmbus_xfer(struct i2c_adapter *adapter,
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)) + goto timeout; + if (I915_READ(GMBUS2 + reg_offset) & + GMBUS_SATOER) + goto clear_err; } }
- if (i + 1 < num && - wait_for(I915_READ(GMBUS2 + reg_offset) & + if (wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE), 50)) goto timeout; @@ -300,15 +298,21 @@ gmbus_xfer(struct i2c_adapter *adapter, goto clear_err; }
+ /* Generate a STOP condition on the bus */ + I915_WRITE(GMBUS1 + reg_offset, GMBUS_CYCLE_STOP | GMBUS_SW_RDY); + /* 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)) + if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, + 10)) { DRM_INFO("GMBUS [%s] timed out waiting for idle\n", adapter->name); + ret = -ETIMEDOUT; + } I915_WRITE(GMBUS0 + reg_offset, 0); - ret = i; + ret = ret ?: i; goto out;
clear_err: