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watchdog: apseed: Add access_cs0 option for alt-boot 

The option for the ast2400/2500 to get access to CS0 at runtime.

Signed-off-by: Ivan Mikhaylov <i.mikhaylov@yadro.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190828102402.13155-5-i.mikhaylov@yadro.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
This commit is contained in:
Ivan Mikhaylov 2019-08-28 13:24:02 +03:00 committed by Wim Van Sebroeck
parent 3d9e89bda9
commit ebdc0f5817
1 changed files with 34 additions and 0 deletions
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@ -72,3 +72,37 @@ Description:
It is a read/write file. When read, the currently assigned It is a read/write file. When read, the currently assigned
pretimeout governor is returned. When written, it sets pretimeout governor is returned. When written, it sets
the pretimeout governor. the pretimeout governor.
What: /sys/class/watchdog/watchdog1/access_cs0
Date: August 2019
Contact: Ivan Mikhaylov <i.mikhaylov@yadro.com>,
Alexander Amelkin <a.amelkin@yadro.com>
Description:
It is a read/write file. This attribute exists only if the
system has booted from the alternate flash chip due to
expiration of a watchdog timer of AST2400/AST2500 when
alternate boot function was enabled with 'aspeed,alt-boot'
devicetree option for that watchdog or with an appropriate
h/w strapping (for WDT2 only).
At alternate flash the 'access_cs0' sysfs node provides:
ast2400: a way to get access to the primary SPI flash
chip at CS0 after booting from the alternate
chip at CS1.
ast2500: a way to restore the normal address mapping
from (CS0->CS1, CS1->CS0) to (CS0->CS0,
CS1->CS1).
Clearing the boot code selection and timeout counter also
resets to the initial state the chip select line mapping. When
the SoC is in normal mapping state (i.e. booted from CS0),
clearing those bits does nothing for both versions of the SoC.
For alternate boot mode (booted from CS1 due to wdt2
expiration) the behavior differs as described above.
This option can be used with wdt2 (watchdog1) only.
When read, the current status of the boot code selection is
shown. When written with any non-zero value, it clears
the boot code selection and the timeout counter, which results
in chipselect reset for AST2400/AST2500.