c894e33ddc
When switching from any MMC speed mode that requires 1.8v (HS200, HS400 and HS400ES) to High Speed (HS) mode, the system ends up configured for SDR12 with a 50MHz clock which is an illegal mode. This happens because the SDHCI_CTRL_VDD_180 bit in the SDHCI_HOST_CONTROL2 register is left set and when this bit is set, the speed mode is controlled by the SDHCI_CTRL_UHS field in the SDHCI_HOST_CONTROL2 register. The SDHCI_CTRL_UHS field will end up being set to 0 (SDR12) by sdhci_set_uhs_signaling() because there is no UHS mode being set. The fix is to change sdhci_set_uhs_signaling() to set the SDHCI_CTRL_UHS field to SDR25 (which is the same as HS) for any switch to HS mode. This was found on a new eMMC controller that does strict checking of the speed mode and the corresponding clock rate. It caused the switch to HS400 mode to fail because part of the sequence to switch to HS400 requires a switch from HS200 to HS before going to HS400. Suggested-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Al Cooper <alcooperx@gmail.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.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.