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> > +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.
