On Wed, Apr 1, 2015 at 7:12 AM, Michael Turquette <mturquette@xxxxxxxxxx> wrote: > Quoting Jassi Brar (2015-03-02 02:28:44) >> On 2 March 2015 at 15:48, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> > On Mon, 02 Mar 2015, Jassi Brar wrote: >> > >> >> On Mon, Mar 2, 2015 at 2:06 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> >> > On Sat, 28 Feb 2015, Jassi Brar wrote: >> >> > >> >> >> On 28 February 2015 at 02:44, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> >> >> > Lots of platforms contain clocks which if turned off would prove fatal. >> >> >> > The only way to recover from these catastrophic failures is to restart >> >> >> > the board(s). Now, when a clock is registered with the framework it is >> >> >> > compared against a list of provided always-on clock names which must be >> >> >> > kept ungated. If it matches, we enable the existing CLK_IGNORE_UNUSED >> >> >> > flag, which will prevent the common clk framework from attempting to >> >> >> > gate it during the clk_disable_unused() procedure. >> >> >> > >> >> >> If a clock is critical on a certain board, it could be got+enabled >> >> >> during early boot so there is always a user. >> >> > >> >> > I tried this. There was push-back from the DT maintainers. >> >> > >> >> > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/324417.html >> >> > >> >> Thanks, I wasn't aware of the history. >> >> >> >> >> To be able to do that from DT, maybe add a new, say, CLK_ALWAYS_ON >> >> >> flag could be made to initialize the clock with one phantom user >> >> >> already. Or just reuse the CLK_IGNORE_UNUSED? >> >> > >> >> > How is that different to what this set is doing? >> >> > >> >> The phantom user - that's there but none can see it. >> >> >> >> How about? >> >> >> >> + of_property_for_each_string(np, "clock-always-on", prop, clkname) { >> >> + clk = __clk_lookup(clkname); >> >> + if (!clk) >> >> + continue; >> >> + >> >> + clk->core->enable_count = 1; >> >> + clk->core->prepare_count = 1; >> >> + } >> > >> > This is only fractionally different from the current implementation. >> > >> > I believe the current way it slightly nicer, as we don't have to fake >> > the user count. >> > >> Well... the user is indeed there, isn't it? It's just not known to >> Linux. So 'fake' isn't most applicable here. >> Otherwise you might have to stub out some existing and future >> functions for CLK_IGNORE_UNUSED. And how do we explain to userspace >> which would see power drawn but no user of the clock? > > Jassi, > > This is broken. What if the parent of this clock has > {enable,prepare}_count of zero? The way we propagate these refcounts up > the tree would fall over. > Yeah it needs to be done at higher level, - clk->core->enable_count = 1; - clk->core->prepare_count = 1; + clk_prepare_enable(clk); cheers! -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
