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

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

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