Messages in this thread | | | Date | Tue, 20 Mar 2012 20:10:34 -0700 | From | Saravana Kannan <> | Subject | Re: [PATCH v7 2/3] clk: introduce the common clock framework |
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On 03/20/2012 04:53 PM, Turquette, Mike wrote: > On Tue, Mar 20, 2012 at 10:46 AM, Saravana Kannan > <skannan@codeaurora.org> wrote: >> On Tue, March 20, 2012 7:02 am, Shawn Guo wrote: >>> On Thu, Mar 15, 2012 at 11:11:19PM -0700, Mike Turquette wrote: >>> ... >>>> +struct clk_ops { >>>> + int (*prepare)(struct clk_hw *hw); >>>> + void (*unprepare)(struct clk_hw *hw); >>>> + int (*enable)(struct clk_hw *hw); >>>> + void (*disable)(struct clk_hw *hw); >>>> + int (*is_enabled)(struct clk_hw *hw); >>>> + unsigned long (*recalc_rate)(struct clk_hw *hw, >>>> + unsigned long parent_rate); >>> >>> I believe I have heard people love the interface with parent_rate >>> passed in. I love that too. But I would like to ask the same thing >>> on .round_rate and .set_rate as well for the same reason why we have >>> it for .recalc_rate. >> >> In my case, for most clocks, set rate involves reparenting. So, what does >> passing parent_rate for these even mean? Passing parent_rate seems more >> apt for recalc_rate since it's called when the parent rate changes -- so, >> the actual parent itself is not expected to change. > > From my conversations with folks across many platforms, I think that > the way your clock tree expects to change rates is the exception, not > the rule. As such you should just ignore the parent_rate parameter as > it useless to you. > >> I could ignore the parameter, but just wondering how many of the others >> see value in this. And if we do add this parameter, it shouldn't be made >> mandatory for the platform driver to use it (due to other assumptions the >> clock framework might make). > > From my rough census of folks that actually need .set_rate support, I > think that everyone except MSM could benefit from this. Your concept > of clk_set_rate is everyone else's clk_set_parent.
To clarify, MSM's set parent is a subset of steps needed to be done to finish set parent. So, it's not that we just randomly decided to swap the meanings of these two functions.
Also, I think don't think the difference in view of set_rate is due to the difference in the clock trees between platforms with complicated trees. I think it's more because of who actually decides the rates for the clock tree. It looks like some platforms pick a top-down approach to deciding the rates of the clock tre while others pick a bottom-up approach.
> Ignoring the new parameter should cause you no harm.
As long as this is guaranteed, I have no problems with Shawn's suggestion.
> 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.
-Saravana
-- 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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