diff options
| author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2018-09-28 21:03:59 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-05 22:29:15 +0200 |
| commit | f139c2558462c04202084c2188bfd81b35b775e3 (patch) | |
| tree | 92f4ed3f72a15f4a251383027472e5547db0b92d | |
| parent | 5f99bd3d9f8da3155da2944383e6ffee30b53383 (diff) | |
drm/dp/mst: Configure no_stop_bit correctly for remote i2c xfers
[ Upstream commit c978ae9bde582e82a04c63a4071701691dd8b35c ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/gpu/drm/drm_dp_mst_topology.c | 1 |
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 b59441d109a5..4a959740058e 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3069,6 +3069,7 @@ 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; |