Re: [PATCH 3/3] ARM: OMAP: AM35xx: fix UART4 softreset

Cousson, Benoit
2012-05-11T09:45:14Z

On 5/11/2012 11:35 AM, Paul Walmsley wrote:
> On Fri, 11 May 2012, Cousson, Benoit wrote:
>
>> On 5/11/2012 11:22 AM, Paul Walmsley wrote:
>>
>>> On the rest of the OMAPs, as far as I know, the UART clocks are all
>>> separate.
>>
>> In fact, not really. The same PER_48M_GFCLK clock is used for every UART
>> instances in OMAP4. We do have a separate modulemode for each UART but as far
>> as clocks are concerned, the source clock is the same.
>
> By "separate" I mean that they are all independently gated. This does not
> appear to be the case with AM3517. Or perhaps it is the case and
> something isn't right with the idle management FSMs.

But they are not separately gated for OMAP4 either. This is the
modulemode trick that make us think that, but it just means that the
PRCM should ensure that this clock is needed when at least one UART
modulemode is enabled. In fact the SPI modules are using the same clock.

The modulemode is used to do some reference counting, but the gating is
done globally. It was the same with the FCK_EN and ICK_EN in OMAP2&3.

The PRCM spec show only one global gating between FUNC_48M_FCLK and
PER_48M_GFCLK. All the modules are sharing the exact same clock.

Regards,
Benoit