Quoting Théo Lebrun (2024-10-24 05:50:16)
> The bug is elsewhere: we do get valid clocks from PL011. Both clk_get()
> calls give proper pointers.
>
> The issue is that we are using `compatible = "fixed-factor-clock"`
> clocks in the middle, and those don't wait for their parents to be
> active.
>
> Simplified clock graph is: pll-per -> occ-periph.
> pll-per is register by our driver. occ-periph looks like:
>
> occ_periph: occ-periph {
> compatible = "fixed-factor-clock";
> clocks = <&olb EQ5C_PLL_PER>;
> #clock-cells = <0>;
> clock-div = <16>;
> clock-mult = <1>;
> };
Why is this fixed factor clk registered from DT vs. from the driver that
registers pll-per? Is it useful to describe it in DT because the factor
can change? Where does it physically exist? In the SoC?
>
> Sequence is:
> - eqc_early_init(): it registers a clock provider that will return
> EPROBE_DEFER for our pll-per.
> - _of_fixed_factor_clk_setup(): it registers occ-periph, even though
> its parent is EPROBE_DEFER. clk_core_populate_parent_map() runs all
> fine without complaining; logical as it doesn't query the clk_hw for
> its parent, it only stores indexes.
> - amba_get_enable_pclk(): it does a clk_get() which works because
> occ-periph exists.
>
> Maybe __clk_register() should check the clk_hw for each parent: if any
> is an EPROBE_DEFER then it should EPROBE_DEFER itself? That looks like
> a rather big behavioral change.
>
> The other solution is to keep as-is: provide all clocks consumed by
> fixed-factor-clocks at of_clk_init() stage.
Another solution is to register the fixed factor clk from the pll-per
clk provider.
And yet another solution is to return EPROBE_DEFER for orphaned clks. We
have everything in place for that but we ran into trouble with consumers
wanting to get orphaned clks in their probe or during assigned-clocks
handling.
