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16681037e7
sdhci_arasan_get_timeout_clock() divides the frequency it has with (1 <<
(13 + divisor)).
However, the divisor is not some Arasan-specific value, but instead is
just the Data Timeout Counter Value from the SDHCI Timeout Control
Register.
Applying it here like this is wrong as the sdhci driver already takes
that value into account when calculating timeouts, and in fact it *sets*
that register value based on how long a timeout is wanted.
Additionally, sdhci core interprets the .get_timeout_clock callback
return value as if it were read from hardware registers, i.e. the unit
should be kHz or MHz depending on SDHCI_TIMEOUT_CLK_UNIT capability bit.
This bit is set at least on the tested Zynq-7000 SoC.
With the tested hardware (SDHCI_TIMEOUT_CLK_UNIT set) this results in
too high a timeout clock rate being reported, causing the core to use
longer-than-needed timeouts. Additionally, on a partitioned MMC
(therefore having erase_group_def bit set) mmc_calc_max_discard()
disables discard support as it looks like controller does not support
the long timeouts needed for that.
Do not apply the extra divisor and return the timeout clock in the
expected unit.
Tested with a Zynq-7000 SoC and a partitioned Toshiba THGBMAG5A1JBAWR
eMMC card.
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Fixes: e3ec3a3d11 ("mmc: arasan: Add driver for Arasan SDHCI")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.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.