diff options
| -rw-r--r-- | drivers/gpu/drm/i915/intel_i2c.c | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 56e437e31580..ae628001fd97 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -435,7 +435,7 @@ gmbus_xfer(struct i2c_adapter *adapter, struct intel_gmbus, adapter); struct drm_i915_private *dev_priv = bus->dev_priv; - int i, reg_offset; + int i = 0, inc, try = 0, reg_offset; int ret = 0; intel_aux_display_runtime_get(dev_priv); @@ -448,12 +448,14 @@ gmbus_xfer(struct i2c_adapter *adapter, reg_offset = dev_priv->gpio_mmio_base; +retry: I915_WRITE(GMBUS0 + reg_offset, bus->reg0); - for (i = 0; i < num; i++) { + for (; i < num; i += inc) { + inc = 1; if (gmbus_is_index_read(msgs, i, num)) { ret = gmbus_xfer_index_read(dev_priv, &msgs[i]); - i += 1; /* set i to the index of the read xfer */ + inc = 2; /* an index read is two msgs */ } else if (msgs[i].flags & I2C_M_RD) { ret = gmbus_xfer_read(dev_priv, &msgs[i], 0); } else { @@ -525,6 +527,18 @@ clear_err: adapter->name, msgs[i].addr, (msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len); + /* + * Passive adapters sometimes NAK the first probe. Retry the first + * message once on -ENXIO for GMBUS transfers; the bit banging algorithm + * has retries internally. See also the retry loop in + * drm_do_probe_ddc_edid, which bails out on the first -ENXIO. + */ + if (ret == -ENXIO && i == 0 && try++ == 0) { + DRM_DEBUG_KMS("GMBUS [%s] NAK on first message, retry\n", + adapter->name); + goto retry; + } + goto out; timeout: |