08e05f4f65
commit 1a8eb6b373c2af6533c13d1ea11f504e5010ed9a upstream.
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: 51ced59cc02e ("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 ============ 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.