81c85ec15a
When retrieveing CD (card detect) and WP (write protect) GPIO handles from the device tree, make sure to assign them active low by default unless the "cd-inverted" or "wp-inverted" properties are set. These properties mean that respective signal is active HIGH since the SDHCI specification stipulates that this kind of signals should be treated as active LOW. If the twocell GPIO flag is also specified as active low, well that's nice and we will silently ignore the tautological specification. If however the GPIO line is specified as active low in the GPIO flasg cell and "cd-inverted" or "wp-inverted" is also specified, the latter takes precedence and we print a warning. The current effect on the MMC slot-gpio core are as follows: For CD GPIOs: no effect. The current code in mmc/core/host.c calls mmc_gpiod_request_cd() with the "override_active_level" argument set to true, which means that whatever the GPIO descriptor thinks about active low/high will be ignored, the core will use the MMC_CAP2_CD_ACTIVE_HIGH to keep track of this and reads the raw value from the GPIO descriptor, totally bypassing gpiolibs inversion semantics. I plan to clean this up at a later point passing the handling of inversion semantics over to gpiolib, so this patch prepares the ground for that. Fow WP GPIOs: this is probably fixing a bug, because the code in mmc/core/host.c calls mmc_gpiod_request_ro() with the "override_active_level" argument set to false, which means it will respect the inversion semantics of the gpiolib and ignore the MMC_CAP2_RO_ACTIVE_HIGH flag for everyone using this through device tree. However the code in host.c confusingly goes to great lengths setting up the MMC_CAP2_RO_ACTIVE_HIGH flag from the GPIO descriptor and by reading the "wp-inverted" property of the node. As far as I can tell this is all in vain and the inversion is broken: device trees that use "wp-inverted" do not work as intended, instead the only way to actually get inversion on a line is by setting the second cell flag to GPIO_ACTIVE_HIGH (which will be the default) or GPIO_ACTIVE_LOW if they want the proper MMC semantics. Presumably all device trees do this right but we need to parse and handle this properly. Cc: linux-mmc@vger.kernel.org Cc: linux-gpio@vger.kernel.org Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
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| Kbuild | ||
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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.