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Jerome Brunet authored
The orphan clocks reparents should migrate any existing count from the orphan clock to its new acestor clocks, otherwise we may have inconsistent counts in the tree and end-up with gated critical clocks Assuming we have two clocks, A and B. * Clock A has CLK_IS_CRITICAL flag set. * Clock B is an ancestor of A which can gate. Clock B gate is left enabled by the bootloader. Step 1: Clock A is registered. Since it is a critical clock, it is enabled. The clock being still an orphan, no parent are enabled. Step 2: Clock B is registered and reparented to clock A (potentially through several other clocks). We are now in situation where the enable count of clock A is 1 while the enable count of its ancestors is 0, which is not good. Step 3: in lateinit, clk_disable_unused() is called, the enable_count of clock B being 0, clock B is gated and and critical clock A actually gets disabled. This situation was found while adding fdiv_clk gates to the meson8b platform. These clocks parent clk81 critical clock, which is the mother of all peripheral clocks in this system. Because of the issue described here, the system is crashing when clk_disable_unused() is called. The situation is solved by reverting commit f8f8f1d0 ("clk: Don't touch hardware when reparenting during registration"). To avoid breaking again the situation described in this commit description, enabling critical clock should be done before walking the orphan list. This way, a parent critical clock may not be accidentally disabled due to the CLK_OPS_PARENT_ENABLE mechanism. Fixes: f8f8f1d0 ("clk: Don't touch hardware when reparenting during registration") Cc: Stephen Boyd <sboyd@codeaurora.org> Cc: Shawn Guo <shawnguo@kernel.org> Cc: Dong Aisheng <aisheng.dong@nxp.com> Signed-off-by:
Jerome Brunet <jbrunet@baylibre.com> Tested-by:
Marek Szyprowski <m.szyprowski@samsung.com> Tested-by:
Heiko Stuebner <heiko@sntech.de> Signed-off-by:
Michael Turquette <mturquette@baylibre.com>
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