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[ Upstream commitfb59ee37cf] If UHS speed modes are enabled, a compatible SD card switches down to 1.8V during enumeration. If after this a software reboot/crash takes place and on-chip ROM tries to enumerate the SD card, the difference in IO voltages (host @ 3.3V and card @ 1.8V) may end up damaging the card. The fix for this is to have support for power cycling the card in hardware (with a PORz/soft-reset line causing a power cycle of the card). Because the beaglebone X15 (rev A,B and C), am57xx-idks and am57xx-evms don't have this capability, disable voltage switching for these boards. The major effect of this is that the maximum supported speed mode is now high speed(50 MHz) down from SDR104(200 MHz). commit88a748419b("ARM: dts: am57xx-idk: Remove support for voltage switching for SD card") did this only for idk boards. Do it for all affected boards. Signed-off-by: Faiz Abbas <faiz_abbas@ti.com> Signed-off-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Sasha Levin <sashal@kernel.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.
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.