Re: [PATCH v2 1/2] drivers/watchdog: Add optional ASPEED device tree properties

Guenter Roeck
2017-06-27T22:07:54Z

On Tue, Jun 27, 2017 at 04:42:24PM -0500, Christopher Bostic wrote:
>
>
> On 6/27/17 4:32 PM, Guenter Roeck wrote:
> >On Tue, Jun 27, 2017 at 04:17:33PM -0500, Christopher Bostic wrote:
> >>Describe device tree optional properties:
> >>
> >> * aspeed,arm-reet - ARM CPU reset on signal
> >> * aspeed,soc-reset - SOC reset on signal
> >> * aspeed,sys-reset - System reset on signal
> >> Disabling system reset may be required in situations where
> >> one of the other watchdog engines in the system is responsible
> >> for this.
> >> * aspeed,interrupt - Interrupt CPU on signal
> >> * aspeed,external-signal - Generate external signal (WDT1 and WDT2 only)
> >> * aspeed,alt-boot - Boot from alternate block on signal
> >>
> >>Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com>
> >>---
> >>v2 - Add 'aspeed,' prefix to all optional properties
> >> - Add arm-reset, soc-reset, interrupt, alt-boot properties
> >>---
> >> .../devicetree/bindings/watchdog/aspeed-wdt.txt | 25 ++++++++++++++++++++++
> >> 1 file changed, 25 insertions(+)
> >>
> >>diff --git a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> >>index c5e74d7..555b8b4 100644
> >>--- a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> >>+++ b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> >>@@ -8,9 +8,34 @@ Required properties:
> >> - reg: physical base address of the controller and length of memory mapped
> >> region
> >>+Optional properties:
> >>+ Signal behavior - Whenever a timeout occurs, the watchdog can be programmed
> >>+ to generate 6 types of signals:
> >>+
> >>+ - aspeed,arm-reset: If property is present then reset ARM CPU only.
> >>+
> >>+ - aspeed,soc-reset: If property is present then reset SOC.
> >>+
> >>+ - aspeed,sys-reset: If property is present then reset the entire chip.
> >>+ In cases where one of the other watchdog engines
> >>+ in the system is responsible for system reset it
> >>+ may be required to not specify this property.
> >>+
> >>+ - aspeed,interrupt: If property is present then interrupt CPU.
> >>+
> >>+ - aspeed,external-signal: If property is present then signal is sent to
> >>+ external reset counter (only WDT1 and WDT2).
> >>+ - aspeed,alt-boot: If property is present then boot from alternate block.
> >>+
> >> Example:
> >> wdt1: watchdog@1e785000 {
> >> compatible = "aspeed,ast2400-wdt";
> >> reg = <0x1e785000 0x1c>;
> >>+ aspeed,arm-reset;
> >>+ aspeed,soc-reset;
> >>+ aspeed,sys-reset;
> >>+ aspeed,interrupt;
> >>+ aspeed,external-signal;
> >>+ aspeed,alt-boot;
> >Is that a bit mask or a value ? I would have thought that,
> >for example, a complete system reset would include the SoC reset,
> >and a SoC reset would include the ARM reset. Generating an
> >interrupt while at the same time resetting the system (or
> >part of it) doesn't seem to make much sense either.
>
> No these aren't bitmasks. The example was intended to indicate what could
> be used.
> In practice only a subset of each of these properties would make any sense.
> How
> would you suggest the example be formatted to convey that? Multiple examples
> I suppose.
>

I would just pick one (which is perfectly fine). After all, it is an example.

Reminds me: Is there a default (eg the chip's default configuration) ?
In other words, what is expected to happen if none of the properties
is specified ?

Thanks,
Guenter