diff options
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 76 | ||||
| -rw-r--r-- | include/drm/drm_dp_helper.h | 5 |
2 files changed, 63 insertions, 18 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index f1283878ff6d..d5368ea56a0f 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -427,11 +427,13 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) * 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. + * + * Returns bytes transferred on success, or a negative error code on failure. */ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { unsigned int retry; - int err; + int ret; /* * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device @@ -440,14 +442,14 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) */ for (retry = 0; retry < 7; retry++) { mutex_lock(&aux->hw_mutex); - err = aux->transfer(aux, msg); + ret = aux->transfer(aux, msg); mutex_unlock(&aux->hw_mutex); - if (err < 0) { - if (err == -EBUSY) + if (ret < 0) { + if (ret == -EBUSY) continue; - DRM_DEBUG_KMS("transaction failed: %d\n", err); - return err; + DRM_DEBUG_KMS("transaction failed: %d\n", ret); + return ret; } @@ -488,9 +490,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) * Both native ACK and I2C ACK replies received. We * can assume the transfer was successful. */ - if (err < msg->size) - return -EPROTO; - return 0; + return ret; case DP_AUX_I2C_REPLY_NACK: DRM_DEBUG_KMS("I2C nack\n"); @@ -513,14 +513,55 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) return -EREMOTEIO; } +/* + * Keep retrying drm_dp_i2c_do_msg until all data has been transferred. + * + * Returns an error code on failure, or a recommended transfer size on success. + */ +static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *orig_msg) +{ + int err, ret = orig_msg->size; + struct drm_dp_aux_msg msg = *orig_msg; + + while (msg.size > 0) { + err = drm_dp_i2c_do_msg(aux, &msg); + if (err <= 0) + return err == 0 ? -EPROTO : err; + + if (err < msg.size && err < ret) { + DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n", + msg.size, err); + ret = err; + } + + msg.size -= err; + msg.buffer += err; + } + + return ret; +} + +/* + * Bizlink designed DP->DVI-D Dual Link adapters require the I2C over AUX + * packets to be as large as possible. If not, the I2C transactions never + * succeed. Hence the default is maximum. + */ +static int dp_aux_i2c_transfer_size __read_mostly = DP_AUX_MAX_PAYLOAD_BYTES; +module_param_unsafe(dp_aux_i2c_transfer_size, int, 0644); +MODULE_PARM_DESC(dp_aux_i2c_transfer_size, + "Number of bytes to transfer in a single I2C over DP AUX CH message, (1-16, default 16)"); + static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num) { struct drm_dp_aux *aux = adapter->algo_data; unsigned int i, j; + unsigned transfer_size; struct drm_dp_aux_msg msg; int err = 0; + dp_aux_i2c_transfer_size = clamp(dp_aux_i2c_transfer_size, 1, DP_AUX_MAX_PAYLOAD_BYTES); + memset(&msg, 0, sizeof(msg)); for (i = 0; i < num; i++) { @@ -538,20 +579,19 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, 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 - * transferring data in larger chunks can actually lead to - * decreased performance. Therefore each message is simply - * transferred byte-by-byte. + /* We want each transaction to be as large as possible, but + * we'll go to smaller sizes if the hardware gives us a + * short reply. */ - for (j = 0; j < msgs[i].len; j++) { + transfer_size = dp_aux_i2c_transfer_size; + for (j = 0; j < msgs[i].len; j += msg.size) { msg.buffer = msgs[i].buf + j; - msg.size = 1; + msg.size = min(transfer_size, msgs[i].len - j); - err = drm_dp_i2c_do_msg(aux, &msg); + err = drm_dp_i2c_drain_msg(aux, &msg); if (err < 0) break; + transfer_size = err; } if (err < 0) break; diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index c5fdc2d3ca97..523f04c90dea 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -42,6 +42,8 @@ * 1.2 formally includes both eDP and DPI definitions. */ +#define DP_AUX_MAX_PAYLOAD_BYTES 16 + #define DP_AUX_I2C_WRITE 0x0 #define DP_AUX_I2C_READ 0x1 #define DP_AUX_I2C_STATUS 0x2 @@ -680,6 +682,9 @@ struct drm_dp_aux_msg { * transactions. The drm_dp_aux_register_i2c_bus() function registers an * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter. + * The I2C adapter uses long transfers by default; if a partial response is + * received, the adapter will drop down to the size given by the partial + * response for this transaction only. * * Note that the aux helper code assumes that the .transfer() function * only modifies the reply field of the drm_dp_aux_msg structure. The |