Re: [PATCH 2/2] ARM: OMAP2+: fix dpll round_rate() to actually round

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

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On 08/05/14 01:16, Paul Walmsley wrote:

>> It's true that the original patch changes the dpll behavior when an
>> exact match is not found. However, I think our drivers always request an
>> exact match, and in that case the original patch doesn't change the
>> behavior in practice.
>>
>> In theory it's possible that a driver requests a non-exact clock from
>> the dpll, and when it gets an error, it does something else.
> 
> The path that worries me at the moment is the set-rate path.  That calls 
> __clk_round_rate() (if the user hasn't called it already) and silently 
> tries to set the clock to the altered rate.

Hmm, so you mean a driver could call set_rate, and presume it only uses
exact rates the dpll can produce, and presumes that set_rate returns an
error if the dpll cannot produce the requested rate?

Isn't that what I said? If a driver has such behavior, I think it still
doesn't work, as (correct me if I'm wrong) we always have the
clk-divider after a dpll. And the clk-divider doesn't handle the error,
so neither can the driver.

Or what kind of scenario do you have in mind?

 Tomi



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