Re: [PATCH v2 3/4] watchdog/aspeed: add support for dual boot

[Guenter Roeck]

On 8/27/19 2:24 AM, Ivan Mikhaylov wrote:
> On Mon, 2019-08-26 at 17:14 -0700, Guenter Roeck wrote:
> > > +/*
> > > + * At alternate side 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.
> > > + *
> > The above needs to be in the sysfs attribute documentation as well.
>
> My apologies but I didn't find any suitable, only watchdog parameters with
> dtbindings file, where should I put it? Documentation/watchdog/aspeed-wdt-
> sysfs.rst?

Documentation/ABI/testing/sysfs-class-watchdog

Guenter

> > > + * This option can be used with wdt2 (watchdog1) only.
> >
> > This implies a specific watchdog numbering which is not guaranteed.
> > Someone might implement a system with some external watchdog.
> >
> > > + */
> > > +static DEVICE_ATTR_RW(access_cs0);
> > > +
> > > +static struct attribute *bswitch_attrs[] = {
> > > +	&dev_attr_access_cs0.attr,
> > > +	NULL
> > > +};
> > > +ATTRIBUTE_GROUPS(bswitch);
> > > +
> > >    static const struct watchdog_ops aspeed_wdt_ops = {
> > >    	.start		= aspeed_wdt_start,
> > >    	.stop		= aspeed_wdt_stop,
> > > @@ -306,9 +359,16 @@ static int aspeed_wdt_probe(struct platform_device
> > > *pdev)
> > >    	}
> > >    
> > >    	status = readl(wdt->base + WDT_TIMEOUT_STATUS);
> > > -	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY)
> > > +	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY) {
> > >    		wdt->wdd.bootstatus = WDIOF_CARDRESET;
> > >    
> > > +		if (of_device_is_compatible(np, "aspeed,ast2400-wdt") ||
> > > +			of_device_is_compatible(np, "aspeed,ast2500-wdt"))
> > > +			wdt->wdd.groups = bswitch_groups;
>
> > Kind of odd that the attribute only exists if the system booted from the
> > second flash, but if that is what you want I won't object. Just make sure
> > that this is explained properly.
> Perhaps dts configuration option would be better solution for it then? "force-
> cs0-switch" as example? Also, if it would be an option, dtbindings/wdt file for

You said earlier that this can not be done automatically but _must_ be done
from user space after the system has booted. Otherwise you could just
automatically switch to cs0 when the driver probes.

As I said, all I am asking for is proper documentation.

Guenter

> documentation will be the right place for it. Usage of this at side 0 will not
> get any good/bad results, it just makes user confused, so I decided to put it
> only at side 1. It works only for ast2400/2500 board unfortunately, for 2600
> there is big difference in switching mechanism. Any other thoughts how to make
> it better?
>
> Thanks.