5fc3d80ef4
Per SDIO Simplified Specification V3, section 3.1.2, A host that supports UHS-I sets S18R to 1 in the argument of CMD5 to request a change of the signal voltage to 1.8V. If the card supports UHS-I and the current signal voltage is 3.3V, S18A is set to 1 in the R4 response. If the signal voltage is already 1.8V, the card sets S18A to 0 so that host maintains the current signal voltage. UHS-I is supported in SD mode and S18A is always 0 in SPI mode. For the current code, if the signaling voltage is fixed 1.8v, so the card will set S18A to 0 for rocr and thus we would clear the R4_18V_PRESENT from ocr, which make core won't try to use uhs mode. To fix it, we expect sdio_read_cccr would fail if the uhs mode won't work at all. Note that it's interesting that some sdio cards still response S18A even the voltage is fixed to 1.8v and the CMD11 will also accepted and finish enabling UHS mode successfully. I guess this is why folks didn't notice this problem. Anyway, fix it. Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> |
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README
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.