On Tue, Dec 17, 2013 at 05:20:07PM +0100, Thierry Reding wrote:
Implements an I2C-over-AUX I2C adapter on top of the generic drm_dp_aux infrastructure. It extracts the retry logic from existing drivers, which should help in porting those drivers to this new helper.
Signed-off-by: Thierry Reding treding@nvidia.com
drivers/gpu/drm/drm_dp_helper.c | 178 ++++++++++++++++++++++++++++++++++++++++ include/drm/drm_dp_helper.h | 4 + 2 files changed, 182 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 01a8173c6e83..8a64cf8ac8cc 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -555,3 +555,181 @@ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
return 0; }
+/*
- I2C-over-AUX implementation
- */
+struct drm_dp_i2c_adapter {
- struct i2c_adapter adapter;
- struct drm_dp_aux *aux;
+};
I'd just embedded an i2c adapter into the drm_dp_aux structure - I think drivers always want such a thing. Then maybe rename the setup function from add to register_i2c_bus or so. For smoother transition drivers can always store a pointer to this i2c_adapter somewhere more convenient for them. -Daniel
+static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) +{
- return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
I2C_FUNC_SMBUS_READ_BLOCK_DATA |I2C_FUNC_SMBUS_BLOCK_PROC_CALL |I2C_FUNC_10BIT_ADDR;+}
+/*
- Transfer a single I2C-over-AUX message and handle various error conditions,
- retrying the transaction as appropriate.
- */
+static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) +{
- unsigned int retry;
- int err;
- /*
* DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device* is required to retry at least seven times upon receiving AUX_DEFER* before giving up the AUX transaction.*/- for (retry = 0; retry < 7; retry++) {
err = aux->transfer(aux, msg);if (err < 0)return err;switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {case DP_AUX_NATIVE_REPLY_ACK:/** For I2C-over-AUX transactions this isn't enough, we* need to check for the I2C ACK reply.*/break;case DP_AUX_NATIVE_REPLY_NACK:return -EREMOTEIO;case DP_AUX_NATIVE_REPLY_DEFER:/** We could check for I2C bitrate capabilities and if* available adjust this interval. We could also be* more careful with DP-to-legacy adapters where a* long legacy cable may forc very low I2C bit rates.** For now just defer for long enough to hopefully be* safe for all use-cases.*/usleep_range(500, 600);continue;default:DRM_ERROR("invalid native reply %#04x\n", msg->reply);return -EREMOTEIO;}switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {case DP_AUX_I2C_REPLY_ACK:/** Both native ACK and I2C ACK replies received. We* can assume the transfer was successful.*/return 0;case DP_AUX_I2C_REPLY_NACK:return -EREMOTEIO;case DP_AUX_I2C_REPLY_DEFER:usleep_range(400, 500);continue;default:DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);return -EREMOTEIO;}- }
- DRM_ERROR("too many retries, giving up\n");
- return -EREMOTEIO;
+}
+static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
int num)+{
- struct drm_dp_i2c_adapter *dp = adapter->algo_data;
- unsigned int i, j;
- for (i = 0; i < num; i++) {
struct drm_dp_aux_msg msg;int err;/** 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.*/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 (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(dp->aux, &msg);if (err < 0)return err;}- }
- return num;
+}
+static const struct i2c_algorithm drm_dp_i2c_algo = {
- .functionality = drm_dp_i2c_functionality,
- .master_xfer = drm_dp_i2c_xfer,
+};
+/**
- drm_dp_add_i2c_bus() - register an I2C adapter for I2C-over-AUX access
- @aux: DisplayPort AUX channel
- Returns a pointer to an I2C adapter on success or an ERR_PTR()-encoded
- error code on failure.
- */
+struct i2c_adapter *drm_dp_add_i2c_bus(struct drm_dp_aux *aux) +{
- struct drm_dp_i2c_adapter *adapter;
- int err;
- adapter = kzalloc(sizeof(*adapter), GFP_KERNEL);
- if (!adapter)
return ERR_PTR(-ENOMEM);- adapter->adapter.algo = &drm_dp_i2c_algo;
- adapter->adapter.algo_data = adapter;
- adapter->adapter.retries = 3;
- adapter->aux = aux;
- adapter->adapter.class = I2C_CLASS_DDC;
- adapter->adapter.owner = THIS_MODULE;
- adapter->adapter.dev.parent = aux->dev;
- adapter->adapter.dev.of_node = aux->dev->of_node;
- strncpy(adapter->adapter.name, dev_name(aux->dev),
sizeof(adapter->adapter.name));- err = i2c_add_adapter(&adapter->adapter);
- if (err < 0) {
kfree(adapter);return ERR_PTR(err);- }
- return &adapter->adapter;
+} +EXPORT_SYMBOL(drm_dp_add_i2c_bus); diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index bad9ee11a2e2..c4acdbc2a172 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -423,6 +423,8 @@ struct drm_dp_aux_msg {
- @transfer: transfers a message representing a single AUX transaction
*/ struct drm_dp_aux {
- struct device *dev;
- ssize_t (*transfer)(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg);
}; @@ -494,4 +496,6 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link); */ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
+struct i2c_adapter *drm_dp_add_i2c_bus(struct drm_dp_aux *aux);
#endif /* _DRM_DP_HELPER_H_ */
1.8.4.2
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