Re: [PATCH 1/3] clk: ti: add 'ti,round-rate' flag

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 12/05/14 15:02, Tero Kristo wrote:
> On 05/08/2014 12:06 PM, Tomi Valkeinen wrote:
>> The current DPLL code does not try to round the clock rate, and instead
>> returns an error if the requested clock rate cannot be produced exactly
>> by the DPLL.
>>
>> It could be argued that this is a bug, but as the current drivers may
>> depend on that behavior, a new flag 'ti,round-rate' is added which
>> enables clock rate rounding.
> 
> Someone could probably argue that this flag is not a hardware feature,

I fully agree.

> but instead is used to describe linux-kernel behavior, and would
> probably be frowned upon by the DT enthusiasts. Othen than that, I like
> this approach better than a global setting, but would like second
> opinions here.

I think the dpll code should always do rounding. That's what
round_rate() is supposed to do, afaik. The current behavior of not
rounding and returning an error is a bug in my opinion.

So, if you ask me, the whole flag is just for the purpose of keeping the
current drivers working, which could depend on the broken behavior. But
I think we cannot have such drivers (functional, at least) in any case,
as the clk-divider driver is broken and doesn't handle the errors the
dpll code currently returns for non-exact rates.

 Tomi



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