2023-04-11 19:26:21

by Brian Masney

Subject: [PATCH] docs: clk: add documentation to log which clocks have been disabled

The existing clk documentation has a section that talks about the
clk_ignore_unused kernel parameter. Add additional documentation that
describes how to log which clocks the kernel disables on bootup. This
will log messages like the following to the console on bootup:

[ 1.268115] clk: Disabling unused clocks
[ 1.272167] clk_disable: gcc_usb_clkref_en
[ 1.276389] clk_disable: gcc_usb30_sec_sleep_clk
[ 1.281131] clk_disable: gcc_usb30_prim_sleep_clk
...

Signed-off-by: Brian Masney <[email protected]>
---
Documentation/driver-api/clk.rst | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/Documentation/driver-api/clk.rst b/Documentation/driver-api/clk.rst
index 3cad45d14187..2199c0042e75 100644
--- a/Documentation/driver-api/clk.rst
+++ b/Documentation/driver-api/clk.rst
@@ -258,6 +258,11 @@ clocks properly but rely on them being on from the bootloader, bypassing
the disabling means that the driver will remain functional while the issues
are sorted out.

+You can see which clocks have been disabled by booting your kernel with these
+parameters:
+
+ tp_printk trace_event=clk:clk_disable
+
To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
kernel.

--
2.39.2

2023-04-20 16:23:01

by Jonathan Corbet

Subject: Re: [PATCH] docs: clk: add documentation to log which clocks have been disabled

Brian Masney <[email protected]> writes:

> The existing clk documentation has a section that talks about the
> clk_ignore_unused kernel parameter. Add additional documentation that
> describes how to log which clocks the kernel disables on bootup. This
> will log messages like the following to the console on bootup:
>
> [ 1.268115] clk: Disabling unused clocks
> [ 1.272167] clk_disable: gcc_usb_clkref_en
> [ 1.276389] clk_disable: gcc_usb30_sec_sleep_clk
> [ 1.281131] clk_disable: gcc_usb30_prim_sleep_clk
> ...
>
> Signed-off-by: Brian Masney <[email protected]>
> ---
> Documentation/driver-api/clk.rst | 5 +++++
> 1 file changed, 5 insertions(+)

I've applied this, but...

> diff --git a/Documentation/driver-api/clk.rst b/Documentation/driver-api/clk.rst
> index 3cad45d14187..2199c0042e75 100644
> --- a/Documentation/driver-api/clk.rst
> +++ b/Documentation/driver-api/clk.rst
> @@ -258,6 +258,11 @@ clocks properly but rely on them being on from the bootloader, bypassing
> the disabling means that the driver will remain functional while the issues
> are sorted out.
>
> +You can see which clocks have been disabled by booting your kernel with these
> +parameters:

...I took the liberty of making that "parameters::" so that the options
would be formatted as a literal block.

> + tp_printk trace_event=clk:clk_disable
> +
> To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
> kernel.

Thanks,

jon