diff options
Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 55 |
1 files changed, 35 insertions, 20 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 27671489477d..4b6e6f3ba0a1 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -577,7 +577,9 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) /* * Transfer a single I2C-over-AUX message and handle various error conditions, - * retrying the transaction as appropriate. + * retrying the transaction as appropriate. It is assumed that the + * aux->transfer function does not modify anything in the msg other than the + * reply field. */ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { @@ -665,11 +667,26 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, { struct drm_dp_aux *aux = adapter->algo_data; unsigned int i, j; + struct drm_dp_aux_msg msg; + int err = 0; - for (i = 0; i < num; i++) { - struct drm_dp_aux_msg msg; - int err; + memset(&msg, 0, sizeof(msg)); + for (i = 0; i < num; i++) { + msg.address = msgs[i].addr; + msg.request = (msgs[i].flags & I2C_M_RD) ? + DP_AUX_I2C_READ : + DP_AUX_I2C_WRITE; + msg.request |= DP_AUX_I2C_MOT; + /* Send a bare address packet to start the transaction. + * Zero sized messages specify an address only (bare + * address) transaction. + */ + msg.buffer = NULL; + msg.size = 0; + err = drm_dp_i2c_do_msg(aux, &msg); + if (err < 0) + break; /* * Many hardware implementations support FIFOs larger than a * single byte, but it has been empirically determined that @@ -678,30 +695,28 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, * transferred byte-by-byte. */ for (j = 0; j < msgs[i].len; j++) { - memset(&msg, 0, sizeof(msg)); - msg.address = msgs[i].addr; - - msg.request = (msgs[i].flags & I2C_M_RD) ? - DP_AUX_I2C_READ : - DP_AUX_I2C_WRITE; - - /* - * All messages except the last one are middle-of- - * transfer messages. - */ - if ((i < num - 1) || (j < msgs[i].len - 1)) - msg.request |= DP_AUX_I2C_MOT; - msg.buffer = msgs[i].buf + j; msg.size = 1; err = drm_dp_i2c_do_msg(aux, &msg); if (err < 0) - return err; + break; } + if (err < 0) + break; } + if (err >= 0) + err = num; + /* Send a bare address packet to close out the transaction. + * Zero sized messages specify an address only (bare + * address) transaction. + */ + msg.request &= ~DP_AUX_I2C_MOT; + msg.buffer = NULL; + msg.size = 0; + (void)drm_dp_i2c_do_msg(aux, &msg); - return num; + return err; } static const struct i2c_algorithm drm_dp_i2c_algo = { |