This is a note to let you know that I've just added the patch titled

drm: Add retries for lspcon mode detection

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: drm-add-retries-for-lspcon-mode-detection.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Dec 20 18:17:52 CET 2017

From: Shashank Sharma shashank.sharma@intel.com Date: Thu, 12 Oct 2017 22:10:08 +0530 Subject: drm: Add retries for lspcon mode detection

From: Shashank Sharma shashank.sharma@intel.com

[ Upstream commit f687e25a7a245952349f1f9f9cc238ac5a3be258 ]

From the CI builds, its been observed that during a driver

reload/insert, dp dual mode read function sometimes fails to read from LSPCON device over i2c-over-aux channel.

This patch: - adds some delay and few retries, allowing a scope for these devices to settle down and respond. - changes one error log's level from ERROR->DEBUG as we want to call it an error only after all the retries are exhausted.

V2: Addressed review comments from Jani (for loop for retry) V3: Addressed review comments from Imre (break on partial read too) V3: Addressed review comments from Ville/Imre (Add the retries exclusively for LSPCON, not for all dp_dual_mode devices) V4: Added r-b from Imre, sending it to dri-devel (Jani)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102294 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102295 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102359 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103186 Cc: Ville Syrjala ville.syrjala@linux.intel.com Cc: Imre Deak imre.deak@intel.com Cc: Jani Nikula jani.nikula@linux.intel.com Reviewed-by: Imre Deak imre.deak@intel.com Acked-by: Dave Airlie airlied@gmail.com Signed-off-by: Shashank Sharma shashank.sharma@intel.com Signed-off-by: Jani Nikula jani.nikula@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/1507826408-19322-1-git-send-em... Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/drm_dp_dual_mode_helper.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c @@ -410,6 +410,7 @@ int drm_lspcon_get_mode(struct i2c_adapt { u8 data; int ret = 0; + int retry;

if (!mode) { DRM_ERROR("NULL input\n"); @@ -417,10 +418,19 @@ int drm_lspcon_get_mode(struct i2c_adapt }

/* Read Status: i2c over aux */ - ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE, - &data, sizeof(data)); + for (retry = 0; retry < 6; retry++) { + if (retry) + usleep_range(500, 1000); + + ret = drm_dp_dual_mode_read(adapter, + DP_DUAL_MODE_LSPCON_CURRENT_MODE, + &data, sizeof(data)); + if (!ret) + break; + } + if (ret < 0) { - DRM_ERROR("LSPCON read(0x80, 0x41) failed\n"); + DRM_DEBUG_KMS("LSPCON read(0x80, 0x41) failed\n"); return -EFAULT; }

Patches currently in stable-queue which might be from shashank.sharma@intel.com are

queue-4.14/drm-add-retries-for-lspcon-mode-detection.patch