From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sasha Levin <sashal@kernel.org>, Brian Vincent <brainn@gmail.com>,
dri-devel@lists.freedesktop.org
Subject: [PATCH AUTOSEL 3.18 41/41] drm/dp/mst: Configure no_stop_bit correctly for remote i2c xfers
Date: Wed, 27 Mar 2019 14:25:18 -0400 [thread overview]
Message-ID: <20190327182518.19394-41-sashal@kernel.org> (raw)
In-Reply-To: <20190327182518.19394-1-sashal@kernel.org>
From: Ville Syrjälä <ville.syrjala@linux.intel.com>
[ 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 7113c95f5ad0..e4c8c594ea15 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2816,6 +2816,7 @@ 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
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
prev parent reply other threads:[~2019-03-27 18:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190327182518.19394-1-sashal@kernel.org>
2019-03-27 18:25 ` [PATCH AUTOSEL 3.18 27/41] fbdev: fbmem: fix memory access if logo is bigger than the screen Sasha Levin
2019-03-27 18:25 ` Sasha Levin [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190327182518.19394-41-sashal@kernel.org \
--to=sashal@kernel.org \
--cc=brainn@gmail.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=linux-kernel@vger.kernel.org \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox