On Mon, 2019-08-26 at 17:14 -0700, Guenter Roeck wrote:

quoted

+/*
+ * 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?

quoted

+ * 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.

quoted

+ */
+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
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.