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authorVille Syrjälä <ville.syrjala@linux.intel.com>2018-09-28 21:03:59 +0300
committerVille Syrjälä <ville.syrjala@linux.intel.com>2018-12-10 22:33:20 +0200
commitc978ae9bde582e82a04c63a4071701691dd8b35c (patch)
parent32658d2c8073699473c28b67f14ad51403ccec5d (diff)
drm/dp/mst: Configure no_stop_bit correctly for remote i2c xfers
We aren't supposed to force a stop+start between every i2c msg when performing multi message transfers. This should eg. cause the DDC segment address to be reset back to 0 between writing the segment address and reading the actual EDID extension block. To quote the E-DDC spec: "... this standard requires that the segment pointer be reset to 00h when a NO ACK or a STOP condition is received." Since we're going to touch this might as well consult the I2C_M_STOP flag to determine whether we want to force the stop or not. Cc: Brian Vincent <brainn@gmail.com> References: https://bugs.freedesktop.org/show_bug.cgi?id=108081 Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180928180403.22499-1-ville.syrjala@linux.intel.com Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index a9b684f14d14..229ad6026314 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3287,6 +3287,7 @@ static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs
msg.u.i2c_read.transactions[i].i2c_dev_id = msgs[i].addr;
msg.u.i2c_read.transactions[i].num_bytes = msgs[i].len;
msg.u.i2c_read.transactions[i].bytes = msgs[i].buf;
+ msg.u.i2c_read.transactions[i].no_stop_bit = !(msgs[i].flags & I2C_M_STOP);
msg.u.i2c_read.read_i2c_device_id = msgs[num - 1].addr;
msg.u.i2c_read.num_bytes_read = msgs[num - 1].len;