RE: [PATCH v6 01/20] clk: bump stdout clock usage for earlycon

Subject: Re: [PATCH v6 01/20] clk: bump stdout clock usage for
earlycon

Hi Peng,

On Fri, 2024-08-09 at 07:16 +0000, Peng Fan wrote:

quoted

quoted

+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?

I not have good idea here. Put of_clk_drop_stdout_clocks after
bootconsole disabled might be ok.

Regards,
Peng.

quoted

quoted

+
 /**
  * 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

quoted

quoted

*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'