From 972e31ba4bc2cd60e2bc955da292b07830543ff4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 28 Sep 2018 21:03:59 +0300 Subject: [PATCH] drm/dp/mst: Configure no_stop_bit correctly for remote i2c xfers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ 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 References: https://bugs.freedesktop.org/show_bug.cgi?id=108081 Signed-off-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20180928180403.22499-1-ville.syrjala@linux.intel.com Reviewed-by: Dhinakaran Pandiyan Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_dp_mst_topology.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d708472d93c4..65f58e23e03d 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3278,6 +3278,7 @@ 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; -- GitLab