From mboxrd@z Thu Jan 1 00:00:00 1970 From: skannan@codeaurora.org (Saravana Kannan) Date: Fri, 23 Mar 2012 15:12:37 -0700 Subject: [PATCH v7 2/3] clk: introduce the common clock framework In-Reply-To: References: <1331878280-2758-1-git-send-email-mturquette@linaro.org> <1331878280-2758-3-git-send-email-mturquette@linaro.org> <20120320140220.GE32469@S2101-09.ap.freescale.net> <4F6946AA.4070201@codeaurora.org> <4F6CEC0C.4060704@codeaurora.org> Message-ID: <4F6CF555.4080109@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/23/2012 02:39 PM, Turquette, Mike wrote: > On Fri, Mar 23, 2012 at 2:33 PM, Saravana Kannan 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 -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.