From ccdb516e1873d9c69377bfec1e3392f3ed660102 Mon Sep 17 00:00:00 2001 From: Alex Deucher Date: Mon, 7 Apr 2014 10:33:44 -0400 Subject: drm/dp/i2c: send bare addresses to properly reset i2c connections (v4) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We need bare address packets at the start and end of each i2c over aux transaction to properly reset the connection between transactions. This mirrors what the existing dp i2c over aux algo currently does. This fixes EDID fetches on certain monitors especially with dp bridges. v2: update as per Ville's comments - Set buffer to NULL for zero sized packets - abort the entre transaction if one of the messages fails v3: drop leftover debugging code v4: integrate Thierry's comments - add comments about address only transactions - switch back to i and j Signed-off-by: Alex Deucher Cc: Ville Syrjälä Cc: Jani Nikula Cc: Thierry Reding Reviewed-by: Ville Syrjälä Signed-off-by: Christian König --- drivers/gpu/drm/drm_dp_helper.c | 51 ++++++++++++++++++++++++++--------------- 1 file changed, 32 insertions(+), 19 deletions(-) (limited to 'drivers/gpu/drm/drm_dp_helper.c') diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 27671489477d..bcfb0d07718e 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -665,11 +665,26 @@ 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 +693,28 @@ 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 = { -- cgit v1.2.3 From 732d50b431dca2f3f78fc21ba9b7ed9d06bb01ce Mon Sep 17 00:00:00 2001 From: Alex Deucher Date: Mon, 7 Apr 2014 10:33:45 -0400 Subject: drm/dp/i2c: Update comments about common i2c over dp assumptions (v3) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If you are using the common dp over i2c functionality, it is asumed that the aux transfer function does not modify the any of the msg structure other than the reply field. Doing so breaks the logic in the common code. v2: update struct drm_dp_aux comments about assumptions v3 (chk): rebased on upstream changes Signed-off-by: Alex Deucher Cc: Ville Syrjälä Cc: Jani Nikula Cc: Thierry Reding Reviewed-by: Ville Syrjälä Signed-off-by: Christian König --- drivers/gpu/drm/drm_dp_helper.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/drm_dp_helper.c') diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index bcfb0d07718e..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) { -- cgit v1.2.3