libbsd zynqmp cpu freq for slcr calc

[Kinsey Moore]

On 10/14/2021 10:18, Joel Sherrill wrote:
> On Thu, Oct 14, 2021 at 9:56 AM Kinsey Moore <kinsey.moore at oarcorp.com> wrote:
>> On 10/14/2021 01:40, Chris Johns wrote:
>>> Hi,
>>>
>>> I have come across this define in zynqmp_slcr.h:
>>>
>>> #define ZYNQMP_DEFAULT_PS_CLK_FREQUENCY 33333333
>>>
>>> What if the cpu freq is changed by a user? If this value still valid?
>> If CPU frequency scaling is used, I believe this value remains
>> unchanged. This is the base clock of the processing subsystem as a whole
>> which includes all hard peripherals.
>>> The CPU frequency is under the control system designer in these parts.
>> That's correct, this frequency could theoretically be changed by using
>> different parts on the board, different dividers somewhere, or probably
>> even forcing the PL to somehow generate the clock. This clock value has
>> been the same for all 3 ZynqMP boards I have on hand.
> If it can be changed by a user, should it be something that can be overridden
> by configuration?

Yes, but it hasn't come up yet and so allowing for an override hasn't 
been a priority. This might be one of those things that is best 
configured in RTEMS since it's BSP-related configuration pertaining to a 
device, but would appear to be dead code/configuration since nothing 
there uses it.


Kinsey