diff options
Diffstat (limited to 'drivers/gpu/drm/i915/intel_i2c.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_i2c.c | 41 |
1 files changed, 31 insertions, 10 deletions
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index f02e52aca746..9707868881ec 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -324,26 +324,47 @@ gmbus_xfer(struct i2c_adapter *adapter, goto clear_err; } - goto done; + /* 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); + I915_WRITE(GMBUS0 + reg_offset, 0); + ret = i; + goto out; clear_err: + /* + * Wait for bus to IDLE before clearing NAK. + * If we clear the NAK while bus is still active, then it will stay + * active and the next transaction may fail. + */ + if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, + 10)) + DRM_INFO("GMBUS [%s] timed out after NAK\n", adapter->name); + /* Toggle the Software Clear Interrupt bit. This has the effect * of resetting the GMBUS controller and so clearing the * BUS_ERROR raised by the slave's NAK. */ I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT); I915_WRITE(GMBUS1 + reg_offset, 0); + I915_WRITE(GMBUS0 + reg_offset, 0); -done: - /* 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. + DRM_DEBUG_DRIVER("GMBUS [%s] NAK for addr: %04x %c(%d)\n", + adapter->name, msgs[i].addr, + (msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len); + + /* + * 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. */ - if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, 10)) - DRM_INFO("GMBUS [%s] timed out waiting for idle\n", - bus->adapter.name); - I915_WRITE(GMBUS0 + reg_offset, 0); - ret = i; + ret = -ENXIO; goto out; timeout: |