linux-kernel - [PATCH] docs: clk: add documentation to log which clocks have been disabled

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Date:   Tue, 11 Apr 2023 15:21:53 -0400
From:   Brian Masney <bmasney@...hat.com>
To:     corbet@....net, sboyd@...nel.org
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        mturquette@...libre.com, linux-doc@...r.kernel.org
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 <bmasney@...hat.com>
---
 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