mirror of https://gitee.com/openkylin/linux.git
27ed2b3f22
The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can be used as GPIOs in a system. Each pin can be configured as input, output, or a special function for the bridge chip. These are: - GPIO1: SUSPEND Input - GPIO2: DSIA VSYNC - GPIO3: DSIA HSYNC or VSYNC - GPIO4: PWM Let's expose these pins as GPIOs. A few notes: - Access to ti-sn65dsi86 is via i2c so we set "can_sleep". - These pins can't be configured for IRQ. - There are no programmable pulls or other fancy features. - Keeping the bridge chip powered might be expensive. The driver is setup such that if all used GPIOs are only inputs we'll power the bridge chip on just long enough to read the GPIO and then power it off again. Setting a GPIO as output will keep the bridge powered. - If someone releases a GPIO we'll implicitly switch it to an input so we no longer need to keep the bridge powered for it. Because of all of the above limitations we just need to implement a bare-bones GPIO driver. The device tree bindings already account for this device being a GPIO controller so we only need the driver changes for it. NOTE: Despite the fact that these pins are nominally muxable I don't believe it makes sense to expose them through the pinctrl interface as well as the GPIO interface. The special functions are things that the bridge chip driver itself would care about and it can just configure the pins as needed. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> [added pdata->gchip.base = -1;] Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com> Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20200507143354.v5.1.Ia50267a5549392af8b37e67092ca653a59c95886@changeid |
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| fs | ||
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| README | ||
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.