linux-kernel - BD71847 clk driver disables clk-32k-out causing RTC/WDT failure

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Message-ID: <CAJ+vNU1Za2CPGVX3q4HKufsxbL5zRrk1B5CWFpKritetrTs4dA@mail.gmail.com>
Date:   Thu, 1 Sep 2022 15:23:33 -0700
From:   Tim Harvey <tharvey@...eworks.com>
To:     linux-clk <linux-clk@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Fabio Estevam <festevam@...il.com>,
        Shawn Guo <shawnguo@...nel.org>
Cc:     NXP Linux Team <linux-imx@....com>,
        Stephen Boyd <sboyd@...nel.org>,
        Matti Vaittinen <mazziesaccount@...il.com>,
        Michael Turquette <mturquette@...libre.com>
Subject: BD71847 clk driver disables clk-32k-out causing RTC/WDT failure

Greetings,

I've found that the bd71847 clk driver (CONFIG_COMMON_CLK_BD718XX
drivers/clk/clk-bd718x7.c) disables clk-32k-out (the BD71847 C32K_OUT
pin) which is connected IMX8MM RTC_XTALI which ends up disabling the
IMX RTC as well as the IMX WDOG functionality.

You can see this with:
# cat /sys/kernel/debug/clk/clk-32k-out/clk_rate
32768
# cat /sys/kernel/debug/clk/clk-32k-out/clk_enable_count
0
# cat /sys/class/rtc/rtc0/name
snvs_rtc 30370000.snvs:snvs-rtc-lp
# cat /sys/class/rtc/rtc0/time
00:00:03
^^^ time never changes

This happens via clk_unprepare_unused() as nothing is flagging the
clk-32k-out as being used. What should be added to the device-tree to
signify that this clk is indeed necessary and should not be disabled?

Best Regards,

Tim