Re: [PATCH v4 4/4] aspeed/watchdog: Add access_cs0 option for alt-boot
From: Guenter Roeck
Date: Sat Aug 31 2019 - 11:02:00 EST
On Wed, Aug 28, 2019 at 01:24:02PM +0300, Ivan Mikhaylov wrote:
> The option for the ast2400/2500 to get access to CS0 at runtime.
> Signed-off-by: Ivan Mikhaylov <i.mikhaylov@xxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> .../ABI/testing/sysfs-class-watchdog | 34 +++++++++++++++++++
> 1 file changed, 34 insertions(+)
> 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@xxxxxxxxx>,
> + Alexander Amelkin <a.amelkin@xxxxxxxxx>
> + 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.