Re: [PATCH 6/10] watchdog: bcm63xx_wdt: Obtain watchdog clock HZ from "periph" clk

Simon Arlott
2015-11-23T19:00:28Z

On 23/11/15 18:19, Florian Fainelli wrote:
> On 23/11/15 07:02, Jonas Gorski wrote:
>> On Sun, Nov 22, 2015 at 3:07 PM, Simon Arlott <simon-A6De1vDTPLDsq35pWSNszA@public.gmane.org> wrote:
>>> -#define WDT_HZ 50000000 /* Fclk */
>>> +#define WDT_CLK_NAME "periph"
>>
>> @Florian:
>> Is this correct? The comment for the watchdog in 6358_map_part.h and
>> earlier claims that the clock is 40 MHz there, but the code uses 50MHz
>> - is this a bug in the comments or is it a bug taken over from the
>> original broadcom code? I'm sure that the periph clock being 50 MHz
>> even on the older chips is correct, else we'd have noticed that in
>> serial output (where it's also used).
>
> There are references to a Fbus2 clock in documentation, but I could not
> find any actual documentation for its actual clock frequency, I would be
> surprised if this chip would have diverged from the previous and future
> ones and used a 40Mhz clock. 6345 started with a peripheral clock
> running at 50Mhz, and that is true for all chips since then AFAICT.
>
> I agree we would have noticed this with the UART or SPI controllers if
> that was not true, so probably a code glitch here...

I've tested both the timer and the watchdog and they give near perfect
time intervals (within 1-2ms based on printk times over serial) so it'd
be obvious if they were out by 25%.