diff options
Diffstat (limited to 'drivers/gpu/drm/i915/intel_i2c.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_i2c.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 4a9707dd0f9..1991a4408cf 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -396,11 +396,22 @@ 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 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. But we have to be careful to not return + * spurious -ENXIO because that will prevent i2c and drm edid functions + * from retrying. So return -ENXIO only when gmbus properly quiescents - + * timing out seems to happen when there _is_ a ddc chip present, but + * it's slow responding and only answers on the 2nd retry. */ + ret = -ENXIO; if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, - 10)) + 10)) { DRM_DEBUG_KMS("GMBUS [%s] timed out after NAK\n", adapter->name); + ret = -ETIMEDOUT; + } /* Toggle the Software Clear Interrupt bit. This has the effect * of resetting the GMBUS controller and so clearing the @@ -414,14 +425,6 @@ clear_err: 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. - */ - ret = -ENXIO; goto out; timeout: |