On 03/23/2012 02:39 PM, Turquette, Mike wrote:
On Fri, Mar 23, 2012 at 2:33 PM, Saravana Kannanskannan@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?
Thanks, Saravana