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Claudiu Beznea 9f7195da31 power: reset: at91-poweroff: switch to slow clock before shutdown
The SAMA5D2 NRST input signal is resynchronized with the SLCK clock and it
can take up to 2 SLCK cycles (about 90us) for the internal reset to be
effective. During this delay, the VDDCORE current consumption may still be
high (application-dependent) with the VDDCORE regulator already OFF. Under
such conditions, VDDCORE may operate below its operating range leading to
potential register corruption.

To prevent such situation, it is recommended to decrease significantly the
power consumption of the device once the voltage regulator is  turned-off.
This can be achieved by operating the device at a much lower low frequency.

To solve this switch the master clock to slock clock just before writing
shutdown command to shutdown controller.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Suggested-by: Patrice Vilchez <patrice.vilchez@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
2018-09-16 12:31:48 +02:00
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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
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the problems which may result by upgrading your kernel.