From mboxrd@z Thu Jan 1 00:00:00 1970 From: mturquette@linaro.org (Mike Turquette) Date: Tue, 16 Apr 2013 12:58:26 -0700 Subject: [PATCH] clk: Always notify whole subtree when reparenting In-Reply-To: References: Message-ID: <20130416195826.19887.78037@quantum> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Quoting Soren Brinkmann (2013-04-16 10:06:50) > A clock's notifier count only reflects notifiers which are registered > directly for that clock. A reparent operation though affects the whole > subtree because of a potential rate change. > When issuing the pre rate change notifications only the notifier count > for the clock to be changed is considered and notifiers for subclocks > may never be called. Resulting in clocks in the subtree which have > registered notifiers, may receive a POST_- or ABORT_RATE_CHANGE > notification, without a PRE_RATE_CHANGE_NOTIFICATION. > Therefore always traverse the whole subtree when issueing pre rate > change notifications during a reparent operation. > > Signed-off-by: Soren Brinkmann > --- > This should probably be considered an RFC. There may be smarter ways to > resolve this issue. E.g. forward notifier counts upstream the way it is done > with enable counts. > Hi Soren, Thanks for the fix. Some of the core code has changed enough lately that it is worth going through and consolidating/cleaning up. For instance another nice optimization that is related might be something like: diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 20ce67f..15e8b41 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1028,6 +1028,9 @@ static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate) else new_rate = parent_rate; + if (new_rate == clk->rate) + return ret; + /* abort rate change if a driver returns NOTIFY_BAD or NOTIFY_STOP */ if (clk->notifier_count) ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate); However it remains to be seen whether any drivers rely on PRE_RATE_CHANGE notifiers even if the clock rate stays the same. I don't think I'll take your patch for 3.10 since no one has reported a bug with it yet, but I'll roll it into a larger cleanup series after the merge window. Thanks, Mike > S?ren > > > drivers/clk/clk.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index 20ce67f..1179cb5 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -1481,8 +1481,7 @@ int clk_set_parent(struct clk *clk, struct clk *parent) > } > > /* propagate PRE_RATE_CHANGE notifications */ > - if (clk->notifier_count) > - ret = __clk_speculate_rates(clk, p_rate); > + ret = __clk_speculate_rates(clk, p_rate); > > /* abort if a driver objects */ > if (ret & NOTIFY_STOP_MASK) > -- > 1.8.2.1