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authorIvan Mikhaylov <i.mikhaylov@yadro.com>2019-08-28 13:24:02 +0300
committerWim Van Sebroeck <wim@linux-watchdog.org>2019-09-17 09:59:13 +0300
commitebdc0f5817321cd5a45e76c6653adf7c7b1d0aee (patch)
tree58ec9fb5b5ea649383588d9b7e847034374437e1 /Documentation/ABI
parent3d9e89bda9e9f01d55ff72f58d619e77d0c5b248 (diff)
downloadlinux-ebdc0f5817321cd5a45e76c6653adf7c7b1d0aee.tar.xz
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>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-class-watchdog34
1 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-watchdog b/Documentation/ABI/testing/sysfs-class-watchdog
index 6317ade5ad19..675f9b537661 100644
--- a/Documentation/ABI/testing/sysfs-class-watchdog
+++ b/Documentation/ABI/testing/sysfs-class-watchdog
@@ -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.