35ff594b0d
[ Upstream commit 78e31c42261779a01bc73472d0f65f15378e9de3 ]
On msm8998, vblank timeouts are observed because the DSI controller is not
reset properly, which ends up stalling the MDP. This is because the reset
logic is not correct per the hardware documentation.
The documentation states that after asserting reset, software should wait
some time (no indication of how long), or poll the status register until it
returns 0 before deasserting reset.
wmb() is insufficient for this purpose since it just ensures ordering, not
timing between writes. Since asserting and deasserting reset occurs on the
same register, ordering is already guaranteed by the architecture, making
the wmb extraneous.
Since we would define a timeout for polling the status register to avoid a
possible infinite loop, lets just use a static delay of 20 ms, since 16.666
ms is the time available to process one frame at 60 fps.
Fixes: a689554ba6ed ("drm/msm: Initial add DSI connector support")
Cc: Hai Li <hali@codeaurora.org>
Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Reviewed-by: Sean Paul <sean@poorly.run>
[seanpaul renamed RESET_DELAY to DSI_RESET_TOGGLE_DELAY_MS]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191011133939.16551-1-jeffrey.l.hugo@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.