[PATCH 0/2] Improvements to the recent clock rework by marex.

[chiffathefox <chiffathefoxx@gmail.com>]

Symptoms:
I ran into an issue with the generic ccf_clk_divider clock driver. ccf_clk_divider assumes that the pointer passed to clk_divider_recalc_rate() (https://github.com/u-boot/u-boot/blob/master/drivers/clk/clk-divider.c#L80) is the same that was kzalloc()'d during clock registration. This assumption was breaking when calling clk_get_rate() on a clock retrieved via clk_get_by_index(), since clk_get_by_index() returns a copy of `struct clk` rather than the original pointer. For example, in https://github.com/u-boot/u-boot/blob/master/drivers/serial/serial_s5p.c#L131 the serial driver retrieves a clock using clk_get_by_index(), and then indirectly passes a pointer to stack-allocated `struct clk` to clk_divider_recalc_rate(), which breaks the ccf_clk_divider driver.

Description:
The Clock API relies on the fact that you call it's functions with a pointer to the
kzalloc()'d `struct clk`, and not a copy of it. To ensure this, existing
clock drivers use ccf_clk_get_rate() and clk_get_by_id().
The clock rework path missed this fact, and instead was returning names
and pointers for the root device.

Testing:
I tested this on Samsung S10 (exynos9820 SoC) with a custom clock driver
and a device tree. Unfortunately, I don't own any other exynos devices
supported by u-boot.


chiffathefox (2):
  clk: clk_resolve_parent_clk(): resolve external clocks by id
  clk: exynos: do not reparent requested clock

 drivers/clk/clk-uclass.c | 7 ++++++-
 drivers/clk/exynos/clk.c | 1 -
 2 files changed, 6 insertions(+), 2 deletions(-)

-- 
2.34.1

base-commit: d503633a36767d756c7de28305cf0de79440cbc0
branch: clk-rework-improvements