linux-imx

clk: migrate the count of orphaned clocks at init

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 f8f8f1d04494 ("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: f8f8f1d04494 ("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>