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commit1a8eb6b373upstream. BIOS writers have begun the practice of setting 40 ohm eMMC driver strength even though the eMMC may not support it, on the assumption that the kernel will validate the value against the eMMC (Extended CSD DRIVER_STRENGTH [offset 197]) and revert to the default 50 ohm value if 40 ohm is invalid. This is done to avoid changing the value for different boards. Putting aside the merits of this approach, it is clear the eMMC's mask of supported driver strengths is more reliable than the value provided by BIOS. Add validation accordingly. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Fixes:51ced59cc0("mmc: sdhci-pci: Use ACPI DSM to get driver strength for some Intel devices") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20200422111629.4899-1-adrian.hunter@intel.com Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.