[PATCH v7 2/3] clk: introduce the common clock framework
skannan at codeaurora.org
Fri Mar 23 22:12:37 UTC 2012
On 03/23/2012 02:39 PM, Turquette, Mike wrote:
> On Fri, Mar 23, 2012 at 2:33 PM, Saravana Kannan<skannan at codeaurora.org> wrote:
>> On 03/20/2012 08:10 PM, Saravana Kannan wrote:
>>> On 03/20/2012 04:53 PM, Turquette, Mike wrote:
>>>> It does make me
>>>> wonder if it would be a good idea to pass in the parent rate for
>>>> .set_parent, which is analogous to .set_rate in many ways.
>>> I need to think a bit more about this.
>> I was thinking about this. I think the common clock fwk should let the
>> set_parent ops "return" the rate of the clock in addition to passing the
>> rate of the parent in.
>> Say this is a divider clock and some one changes the parent. The cached
>> "rate" of the clock in the clock fwk is no longer correct. So, the clock fwk
>> should also add a "*new_rate" param to set parent ops.
> __clk_recalc_rates is called by __clk_reparent which is called by
> clk_set_parent. __clk_recalc_rates is also called by clk_set_rate.
> Does this not handle the old cached clk->rate for you?
For the set_parent case, ops->recalc_rate() is called twice. Once for
PRE_CHANGE and once for POST_CHANGE. For this clock, I can only really
recalc the rate during the POST_CHANGE call. So, how should I
differentiate the two cases?
On a separate note:
Sorry if I missed any earlier discussion on this, but what's the reason
for calling recalc_rate() pre-change and post-change but without giving
it the ability to differentiate between the two?
I think it's quite useful for recalc_rate to be called pre/post change
(some steps have to be done pre/post change depending on whether the
parent rate is increasing or decreasing). But I don't see the "msg"
being passed along.
Also, I noticed that clk_set_parent() is treating a NULL as an invalid
clock. Should that be fixed? set_parent(NULL) could be treated as a
grounding the clock. Should we let the ops->set_parent determine if NULL
is valid option?
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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