On Tue, Jan 26, 2021 at 01:21:36PM +0200, Abel Vesa wrote:
> Some clocks are already enabled in HW even before the kernel
> starts to boot. So, in order to make sure that these clocks do not
> get disabled when clk_disable_unused call is done or when
> reparenting clocks, we enable them in core on clock registration.
> Such a clock will have to be registered with CLK_IGNORE_UNUSED flag
> and also needs to have the is_enabled ops implemented.
>
> Signed-off-by: Abel Vesa <abel.v...@nxp.com>
> ---
> drivers/clk/clk.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 3d751ae5bc70..26d55851cfa5 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3416,6 +3416,7 @@ static int __clk_core_init(struct clk_core *core)
> int ret;
> struct clk_core *parent;
> unsigned long rate;
> + bool is_hw_enabled = false;
> int phase;
>
> if (!core)
> @@ -3558,12 +3559,20 @@ static int __clk_core_init(struct clk_core *core)
> rate = 0;
> core->rate = core->req_rate = rate;
>
> + /*
> + * If the clock has the CLK_IGNORE_UNUSED flag set and it is already
> + * enabled in HW, enable it in core too so it won't get accidentally
> + * disabled when walking the orphan tree and reparenting clocks
> + */
> + if (core->flags & CLK_IGNORE_UNUSED && core->ops->is_enabled)
> + is_hw_enabled = clk_core_is_enabled(core);
> +
> /*
> * Enable CLK_IS_CRITICAL clocks so newly added critical clocks
> * don't get accidentally disabled when walking the orphan tree and
> * reparenting clocks
> */
> - if (core->flags & CLK_IS_CRITICAL) {
> + if (core->flags & CLK_IS_CRITICAL || is_hw_enabled) {
> unsigned long flags;
>
> ret = clk_core_prepare(core);
This means that a bootloader enabled clock with CLK_IGNORE_UNUSED flag
can effectively never be disabled because the prepare/enable count is 1
without any user. This is the behaviour we want to have with critical
clocks, but I don't think this is desired for clocks with the
CLK_IGNORE_UNUSED flag.
Sascha
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