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 | 42 +++++++++++++++++++++++++------------ 1 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 2cdd531..c3d8c70 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -261,7 +261,7 @@ 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 | (len << GMBUS_BYTE_COUNT_SHIFT) | (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_READ | GMBUS_SW_RDY); @@ -273,7 +273,8 @@ gmbus_xfer(struct i2c_adapter *adapter, (GMBUS_SATOER | GMBUS_HW_RDY), 50)) goto timeout; - if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) + if (I915_READ(GMBUS2 + reg_offset) & + GMBUS_SATOER) goto clear_err;
val = I915_READ(GMBUS3 + reg_offset); @@ -292,20 +293,13 @@ 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 | (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); @@ -313,11 +307,18 @@ 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; @@ -337,9 +338,22 @@ clear_err: ret = -ENXIO;
done: - /* Mark the GMBUS interface as disabled. We will re-enable it at the - * start of the next xfer, till then let it sleep. + if (I915_READ(GMBUS2 + reg_offset) & GMBUS_HW_WAIT_PHASE) { + I915_WRITE(GMBUS1 + reg_offset, + GMBUS_CYCLE_STOP | GMBUS_SW_RDY); + POSTING_READ(GMBUS2 + reg_offset); + } + + /* 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 [%s] timed out waiting for IDLE\n", + adapter->name); + ret = -ETIMEDOUT; + } I915_WRITE(GMBUS0 + reg_offset, 0);
mutex_unlock(&dev_priv->gmbus_mutex);