Re: [PATCH 1/2] Documentation: DT: Add entry for ARM SP805-WDT

Rob Herring
2015-11-18T14:19:31Z

On Wed, Nov 18, 2015 at 8:03 AM, Bhupesh SHARMA <bhupesh.linux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Hi Rob,
>
> Thanks for the review.
>
> On Tue, Nov 17, 2015 at 5:44 AM, Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
>> On Mon, Nov 16, 2015 at 02:45:25PM +0000, Mark Rutland wrote:
>>> On Mon, Nov 16, 2015 at 07:54:42PM +0530, Bhupesh Sharma wrote:
>>> > This patch adds a devicetree binding documentation for ARM's
>>> > SP805 WatchDog Timer.
>>> >
>>> > Signed-off-by: Bhupesh Sharma <bhupesh.sharma-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
>>> > ---
>>> > .../devicetree/bindings/watchdog/sp805-wdt.txt | 33 ++++++++++++++++++++
>>> > 1 file changed, 33 insertions(+)
>>> > create mode 100644 Documentation/devicetree/bindings/watchdog/sp805-wdt.txt
>>> >
>>> > diff --git a/Documentation/devicetree/bindings/watchdog/sp805-wdt.txt b/Documentation/devicetree/bindings/watchdog/sp805-wdt.txt
>>> > new file mode 100644
>>> > index 0000000..ec70fe9
>>> > --- /dev/null
>>> > +++ b/Documentation/devicetree/bindings/watchdog/sp805-wdt.txt
>>> > @@ -0,0 +1,33 @@
>>> > +* ARM SP805 Watchdog Timer (WDT) Controller
>>> > +
>>> > +SP805 WDT is a ARM Primecell Peripheral and has a standard-id register that
>>> > +can be used to identify the peripheral type, vendor, and revision.
>>> > +This value can be used for driver matching.
>>> > +
>
> [snip..]
>
>>> > +As SP805 WDT is a primecell IP, it follows the base bindings specified in
>>> > +'arm/primecell.txt'
>>> > +
>>> > +Required properties:
>>> > +- compatible : Should be "arm,sp805-wdt", "arm,primecell"
>>> > +- reg : Base address and size of the watchdog timer registers.
>>> > +- interrupts : Should specify WDT interrupt number.
>>> > +
>>> > +Optional properties:
>>> > +- clocks : From common clock binding. First clock is phandle to clock for apb
>>> > + pclk. Additional clocks are optional.
>>> > +- clock-names : From common clock binding. Shall be "apb_pclk" for first clock.
>>>
>>> The hardware has "WDOGCLK", which is what the driver appears to expect
>>> first implicitly.
>>
>> The h/w has 2 clocks, PCLK and WDOGCLK, so both should be described and
>> neither should be optional.
>
> As per the SP805 WDT TRM I have with me (see [1], Figure 1-1), this
> h/w has only only input
> clock WDOGCLK.
>
> [1] http://infocenter.arm.com/help/topic/com.arm.doc.ddi0270b/DDI0270.pdf

Look closer, PCLK is in the AMBA bus signals. The version online has
some timing diagrams also which I didn't find here.

Rob