From ccdb516e1873d9c69377bfec1e3392f3ed660102 Mon Sep 17 00:00:00 2001 From: Alex Deucher Date: Mon, 7 Apr 2014 10:33:44 -0400 Subject: [PATCH] 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(-) 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; + + memset(&msg, 0, sizeof(msg)); for (i = 0; i < num; i++) { - struct drm_dp_aux_msg msg; - int err; - + 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 = {