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path: root/drivers/gpu/drm/drm_dp_helper.c
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Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c55
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 = {