Hi Peng,
On Fri, 2024-08-09 at 07:16 +0000, Peng Fan wrote:
> > +static int __init of_clk_drop_stdout_clocks(void) {
> > + for (size_t i = 0; i < of_clk_stdout_clks.n_clks; ++i) {
> > + clk_disable_unprepare(of_clk_stdout_clks.clks[i]);
> > + clk_put(of_clk_stdout_clks.clks[i]);
> > + }
> > +
> > + kfree(of_clk_stdout_clks.clks);
> > +
> > + /*
> > + * Do not try to acquire stdout clocks after late initcalls, e.g.
> > + * during further module loading, as we then wouldn't have a
> > way to
> > + * drop the references (and associated allocations) ever again.
> > + */
> > + of_clk_stdout_clks.bump_refs = false;
> > +
> > + return 0;
> > +}
> > +late_initcall_sync(of_clk_drop_stdout_clocks);
>
> If the uart driver is built as module, this might break earlycon.
> Before uart driver loaded, clk disabled per my understanding.
You're right.
With this in mind, I'm not sure then if a generic solution is possible...
I guess it has to be duplicated into the platforms after all and platforms
can enable this if they opt to disallow uart as module?
Any other suggestions?
> > +
> > /**
> > * struct of_clk_provider - Clock provider registration structure
> > * @link: Entry in global list of clock providers @@ -5031,6 +5156,8
> > @@ int of_clk_add_provider(struct device_node *np,
> >
> > fwnode_dev_initialized(&np->fwnode, true);
> >
> > + of_clk_bump_stdout_clocks();
> > +
> > return ret;
> > }
> > EXPORT_SYMBOL_GPL(of_clk_add_provider);
> > @@ -5073,6 +5200,8 @@ int of_clk_add_hw_provider(struct
> > device_node *np,
> >
> > fwnode_dev_initialized(&np->fwnode, true);
> >
> > + of_clk_bump_stdout_clocks();
>
> If clock driver is built as module, the will make the
> clocks will be always enabled, if my understanding is correct.
until late_initcall_sync(), at which point it'll be disabled before the uart
driver has probed, yes :-(
Cheers,
Andre'
