Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices:
OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
e5400750fa
At the moment, the MSM DSI driver calls drm_panel_enable() rather early
from the DSI bridge pre_enable() function. At this point, the encoder
(e.g. MDP5) is not enabled, so we have not started transmitting
video data.
However, the drm_panel_funcs documentation states that enable()
should be called on the panel *after* video data is being transmitted:
The .prepare() function is typically called before the display controller
starts to transmit video data. [...] After the display controller has
started transmitting video data, it's safe to call the .enable() function.
This will typically enable the backlight to make the image on screen visible.
Calling drm_panel_enable() too early causes problems for some panels:
The TFT LCD panel used in the Samsung Galaxy Tab A 9.7 (2015) (APQ8016)
uses the MIPI_DCS_SET_DISPLAY_BRIGHTNESS command to control
backlight/brightness of the screen. The enable sequence is therefore:
drm_panel_enable()
drm_panel_funcs.enable():
backlight_enable()
backlight_ops.update_status():
mipi_dsi_dcs_set_display_brightness(dsi, bl->props.brightness);
The panel seems to silently ignore the MIPI_DCS_SET_DISPLAY_BRIGHTNESS
command if it is sent too early. This prevents setting the initial brightness,
causing the display to be enabled with minimum brightness instead.
Adding various delays in the panel initialization code does not result
in any difference.
On the other hand, moving drm_panel_enable() to dsi_mgr_bridge_enable()
fixes the problem, indicating that the panel requires the video stream
to be active before the brightness command is accepted.
Therefore: Move drm_panel_enable() to dsi_mgr_bridge_enable() to
delay calling it until video data is being transmitted.
Move drm_panel_disable() to dsi_mgr_bridge_disable() for similar reasons.
(This is not strictly required for the panel affected above...)
Tested-by: Jasper Korten <jja2000@gmail.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Tested-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.