Linux 4.14.111

[thirdparty/kernel/stable-queue.git] / releases / 4.14.111 / drm-dp-mst-configure-no_stop_bit-correctly-for-remot.patch

diff --git a/releases/4.14.111/drm-dp-mst-configure-no_stop_bit-correctly-for-remot.patch b/releases/4.14.111/drm-dp-mst-configure-no_stop_bit-correctly-for-remot.patch
new file mode 100644 (file)
index 0000000..910e2ca
--- /dev/null
+++ b/releases/4.14.111/drm-dp-mst-configure-no_stop_bit-correctly-for-remot.patch
@@ -0,0 +1,48 @@
+From ccce3187be850a2d563aadade41ac1c5d9b6f578 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
+Date: Fri, 28 Sep 2018 21:03:59 +0300
+Subject: 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 <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>
+---
+ 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 2a4cf6837324..bb9a9852ec22 100644
+--- a/drivers/gpu/drm/drm_dp_mst_topology.c
++++ b/drivers/gpu/drm/drm_dp_mst_topology.c
+@@ -3199,6 +3199,7 @@ 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;
+-- 
+2.19.1
+