Subject: [PATCH] ARM: OMAP2+: timer: remove CONFIG_OMAP_32K_TIMER

From: [email-masked] (Jon Hunter)
Date: Thu, 8 Nov 2012 11:58:53 -0600

On 11/08/2012 11:47 AM, Hiremath, Vaibhav wrote:
> On Thu, Nov 08, 2012 at 23:09:57, Hunter, Jon wrote:

[snip]

>> I think you are missing the point here. For OMAP devices we have two
>> main external clock sources which are the 32kHz clock and the sys_clk
>> (can be a range of frequencies from 12-38.4MHz for OMAP4). The point is
>> for OMAP these clock sources are always present and AFAIK there is no
>> h/w configuration that allows you not to have the 32kHz clock source.
>> PRCM needs it and I think for OMAP1 the reset logic needs it (if memory
>> serves).
>>
>> Igor was mentioning a h/w scenario where the 32kHz source is not
>> present. However, I am not sure which devices support this and is
>> applicable too.
>>
>> So we are not discussing the 32k-sync-timer here. We are discussing
>> whether there are any device configurations where a 32k clock source
>> would not be available for the gptimer.
>>
> 
> Exactly that is the point I am trying to make here,
> 
> In case of AM33xx, it is certainly possible to build the system without 
> this 32Khz clock. 
> 
> Interesting point here is, this 32KHz clock is external clock coming from 
> crystal connected to in-built RTC module.

Thanks. Looking at the AM3358 data manual it states ...

"The OSC1 oscillator provides a 32.768-kHz reference clock to the
real-time clock (RTC) and is connected to the RTC_XTALIN and RTC_XTALOUT
terminals. OSC1 is disabled by default after power is applied. This
clock input is optional and may not be required if the RTC is configured
to receive a clock from the internal 32k RC oscillator (CLK_RC32K) or
peripheral PLL (CLK_32KHZ) which receives a reference clock from the
OSC0 input."

So what is clear to me that an external 32k clock source is optional.
However, it still appears that you will always have an internal 32k
source and so regardless of the h/w configuration, a gptimer will always
have an 32k clock available on the AM335x devices. Is that correct?

Jon