[PATCH 0/2] clk: fix the need of booking clk_ignore_unused=true on embedded devs
From: Mauro Carvalho Chehab
Date: Thu Oct 07 2021 - 08:08:25 EST
Currently, the only way to boot a Kernel with drivers built as modules on embedded
devices like HiKey 970 is to pass clk_ignore_unused=true as a modprobe parameter.
There are two separate issues:
1. the clk's core calls clk_disable_unused() too early. By the time this
function is called, only the builtin drivers were already probed/initialized.
Drivers built as modules will only be probed afterwards.
This cause a race condition and boot instability, as the clk core will try
to disable clocks while the drivers built as modules are still being
probed and initialized.
I suspect that the same problem used to happen at the regulator's core,
as there's a code that waits for 30 seconds before disabling unused
regulators;
2. there are some gate clocks defined at HiKey 970 that should always be on,
as otherwise the system will hang, or the filesystem I/O will stop.
Ps.:
I submitted already 3 or 4 versions of patches for HiKey 970 clock, but
they're all unreliable, due to the race conditions at the clk core due to (1).
Patch 1 solves the issue with the clk core.
Patch 2 solves the HiKey 970 specific issues.
Mauro Carvalho Chehab (2):
clk: wait for extra time before disabling unused clocks
clk: clk-hi3670: mark some clocks as CLK_IS_CRITICAL
drivers/clk/clk.c | 51 +++++++++++++++++++-----------
drivers/clk/hisilicon/clk-hi3670.c | 24 +++++++-------
2 files changed, 44 insertions(+), 31 deletions(-)
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2.31.1