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According the JEDEC specification an eMMC card supporting 1.8V vccq in DDR mode should also be capable of 3.3V. However, it's been reported that some mmc hosts supports 3.3V, but not 1.8V. Currently the mmc core implements an error handling when the host fails to set 1.8V for vccq, by falling back to 3.3V. Unfortunate, this seems to be insufficient for some mmc hosts. To enable these to use eMMC DDR mode let's invent a new mmc cap, MMC_CAP_3_3V_DDR, which tells whether they support the eMMC 3.3V DDR mode. In case MMC_CAP_3_3V_DDR is set, but not MMC_CAP_1_8V_DDR, let's change to remain on the 3.3V, as it's the default voltage level for vccq, set by the earlier power up sequence. As this change introduces MMC_CAP_3_3V_DDR, let's take the opportunity to do some re-formatting of the related defines in the header file. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com> Tested-by: Jan Glauber <jglauber@cavium.com> Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
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.