Return -ENXIO if a device NAKs a transaction.
Note: We should return -ETIMEDOUT, too if the transaction times out, however, that error path is currently handled by the 'bit-bang fallback'.
Signed-off-by: Daniel Kurtz djkurtz@chromium.org --- drivers/gpu/drm/i915/intel_i2c.c | 12 +++++++++++- 1 files changed, 11 insertions(+), 1 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 232b7cb..151b828 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -242,6 +242,7 @@ gmbus_xfer(struct i2c_adapter *adapter, adapter); struct drm_i915_private *dev_priv = adapter->algo_data; int i, reg_offset; + int ret = 0;
if (bus->force_bit) return intel_i2c_quirk_xfer(dev_priv, @@ -333,6 +334,15 @@ clear_err: I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT); I915_WRITE(GMBUS1 + reg_offset, 0);
+ /* + * If no ACK is received during the address phase of a transaction, + * the adapter must report -ENXIO. + * It is not clear what to return if no ACK is received at other times. + * So, we always return -ENXIO in all NAK cases, to ensure we send + * it at least during the one case that is specified. + */ + 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. @@ -341,7 +351,7 @@ done:
mutex_unlock(&dev_priv->gmbus_mutex);
- return i; + return ret ?: i;
timeout: DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d [%s]\n",