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Commit ebdc0f58 authored by Ivan Mikhaylov's avatar Ivan Mikhaylov Committed by Wim Van Sebroeck
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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: default avatarIvan Mikhaylov <i.mikhaylov@yadro.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190828102402.13155-5-i.mikhaylov@yadro.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@linux-watchdog.org>
parent 3d9e89bd

Documentation/ABI/testing/sysfs-class-watchdog

+34 −0
Original line number Diff line number Diff line
@@ -72,3 +72,37 @@ Description: 
		It is a read/write file. When read, the currently assigned

		pretimeout governor is returned.  When written, it sets

		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.