| Message ID | 1425071674-16995-4-git-send-email-lee.jones@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Fri, 27 Feb 2015, Lee Jones 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. > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > --- > drivers/clk/clk.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index 61c3fc5..3aab75e 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -2856,6 +2856,9 @@ int of_clk_add_provider(struct device_node *np, > void *data) > { > struct of_clk_provider *cp; > + struct property *prop; > + struct clk *clk; > + const char *clkname; > int ret; > > cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL); > @@ -2875,6 +2878,14 @@ int of_clk_add_provider(struct device_node *np, > if (ret < 0) > of_clk_del_provider(np); > > + of_property_for_each_string(np, "clock-always-on", prop, clkname) { > + clk = __clk_lookup(clkname); > + if (!clk) > + continue; > + > + clk->core->flags |= CLK_IGNORE_UNUSED; Might save a few cycles by breaking here. > + } > + > return ret; > } > EXPORT_SYMBOL_GPL(of_clk_add_provider);
On 28 February 2015 at 02:44, Lee Jones <lee.jones@linaro.org> 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. 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? -Jassi -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, 28 Feb 2015, Maxime Coquelin wrote: > Hi Lee, > > On 02/27/2015 10:14 PM, Lee Jones 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. > > Please correct me if I'm wrong, but your patch does not fix the > issue you had initially. > Let's take an example: > A clock is critical for the system, and should never be gated, so > you add the CLK_IGNORE_UNUSED > flag so that it is not disabled by clk_disable_unused() procedure. > The same clock is also used by other IPs, for example spi 0 instance. > When starting a spi transfer, clk_enable() is called on this clock, > so its usecount becomes 1. > Once transfer done, clk_disable() is called, usecount becomes 0 and > the clock gets disabled: system freeze. You're right. I also need to extend clk_core_disable() to take notice of CLK_IGNORE_UNUSED.
On Sat, 28 Feb 2015, Jassi Brar wrote: > On 28 February 2015 at 02:44, Lee Jones <lee.jones@linaro.org> 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 > 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?
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 61c3fc5..3aab75e 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -2856,6 +2856,9 @@ int of_clk_add_provider(struct device_node *np, void *data) { struct of_clk_provider *cp; + struct property *prop; + struct clk *clk; + const char *clkname; int ret; cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL); @@ -2875,6 +2878,14 @@ int of_clk_add_provider(struct device_node *np, if (ret < 0) of_clk_del_provider(np); + of_property_for_each_string(np, "clock-always-on", prop, clkname) { + clk = __clk_lookup(clkname); + if (!clk) + continue; + + clk->core->flags |= CLK_IGNORE_UNUSED; + } + return ret; } EXPORT_SYMBOL_GPL(of_clk_add_provider);
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. Signed-off-by: Lee Jones <lee.jones@linaro.org> --- drivers/clk/clk.c | 11 +++++++++++ 1 file changed, 11 insertions(+)