[PATCH v3] clk: core: Honor CLK_OPS_PARENT_ENABLE in clk_core_is_enabled

[Stephen Boyd]

Quoting Chen-Yu Tsai (2023-01-03 01:23:30)
> In the previous commits that added CLK_OPS_PARENT_ENABLE, support for
> this flag was only added to rate change operations (rate setting and
> reparent) and disabling unused subtree. It was not added to the
> clock gate related operations. Any hardware driver that needs it for
> these operations will either see bogus results, or worse, hang.
> 
> This has been seen on MT8192 and MT8195, where the imp_ii2_* clk
> drivers set this, but dumping debugfs clk_summary would cause it
> to hang.
> 
> Prepare parent on prepare and enable parent on enable dependencies are
> already handled automatically by the core as part of its sequencing.
> Whether the case for "enable parent on prepare" should be supported by
> this flag or not is not clear, and thus ignored for now.
> 
> This change solely fixes the handling of clk_core_is_enabled, i.e.
> enabling the parent clock when reading the hardware state. Unfortunately
> clk_core_is_enabled is called in a variety of places, sometimes with
> the enable clock already held. To avoid deadlocking, the core will
> ignore readouts and just return false if CLK_OPS_PARENT_ENABLE is set
> but the parent isn't currently enabled.
> 
> Fixes: fc8726a2c021 ("clk: core: support clocks which requires parents enable (part 2)")
> Fixes: a4b3518d146f ("clk: core: support clocks which requires parents enable (part 1)")
> Signed-off-by: Chen-Yu Tsai <wenst at chromium.org>
> ---

Applied to clk-next