[PATCH 1/3] clk: sunxi-ng: add support for rate resetting notifier

[Icenowy Zheng]

在 2023-08-07星期一的 11:36 +0200，Frank Oltmanns写道：
> From: Icenowy Zheng <icenowy at aosc.io>
> 
> In some situaitons, we will want a clock rate be kept while its
> parent
> can change, for example, to make dual-head work on A64, TCON0 clock
> needs to be kept for LCD display and its parent (or grandparent)
> PLL-Video0 need to be changed for HDMI display. (There's a quirk on
> A64
> that HDMI PHY can only use PLL-Video0, not PLL-Video1).
> 
> Add a notifier helper to create such kind of rate keeping notifier by
> reset the rate after the parent changed.
> 
> Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
> ---
>  drivers/clk/sunxi-ng/ccu_common.c | 22 ++++++++++++++++++++++
>  drivers/clk/sunxi-ng/ccu_common.h | 12 ++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_common.c b/drivers/clk/sunxi-
> ng/ccu_common.c
> index 8d28a7a079d0..434fa46ad460 100644
> --- a/drivers/clk/sunxi-ng/ccu_common.c
> +++ b/drivers/clk/sunxi-ng/ccu_common.c
> @@ -87,6 +87,28 @@ int ccu_pll_notifier_register(struct ccu_pll_nb
> *pll_nb)
>  }
>  EXPORT_SYMBOL_NS_GPL(ccu_pll_notifier_register, SUNXI_CCU);
>  
> +static int ccu_rate_reset_notifier_cb(struct notifier_block *nb,
> +                                     unsigned long event, void
> *data)
> +{
> +       struct ccu_rate_reset_nb *rate_reset =
> to_ccu_rate_reset_nb(nb);
> +
> +       if (event == PRE_RATE_CHANGE) {
> +               rate_reset->saved_rate = clk_get_rate(rate_reset-
> >target_clk);

In fact I think we should have a better way to save the intended clock
rate ;-)

> +       } else if (event == POST_RATE_CHANGE) {
> +               clk_set_rate(rate_reset->target_clk, rate_reset-
> >saved_rate);
> +       }
> +
> +       return NOTIFY_DONE;
> +}
> +
> +int ccu_rate_reset_notifier_register(struct ccu_rate_reset_nb
> *rate_reset_nb)
> +{
> +       rate_reset_nb->clk_nb.notifier_call =
> ccu_rate_reset_notifier_cb;
> +
> +       return clk_notifier_register(rate_reset_nb->common->hw.clk,
> +                                    &rate_reset_nb->clk_nb);
> +}
> +
>  static int sunxi_ccu_probe(struct sunxi_ccu *ccu, struct device
> *dev,
>                            struct device_node *node, void __iomem
> *reg,
>                            const struct sunxi_ccu_desc *desc)
> diff --git a/drivers/clk/sunxi-ng/ccu_common.h b/drivers/clk/sunxi-
> ng/ccu_common.h
> index fbf16c6b896d..6b0b05fae123 100644
> --- a/drivers/clk/sunxi-ng/ccu_common.h
> +++ b/drivers/clk/sunxi-ng/ccu_common.h
> @@ -69,4 +69,16 @@ int devm_sunxi_ccu_probe(struct device *dev, void
> __iomem *reg,
>  void of_sunxi_ccu_probe(struct device_node *node, void __iomem *reg,
>                         const struct sunxi_ccu_desc *desc);
>  
> +struct ccu_rate_reset_nb {
> +       struct notifier_block   clk_nb;
> +       struct ccu_common       *common;
> +
> +       struct clk              *target_clk;
> +       unsigned long           saved_rate;
> +};
> +
> +#define to_ccu_rate_reset_nb(_nb) container_of(_nb, struct
> ccu_rate_reset_nb, clk_nb)
> +
> +int ccu_rate_reset_notifier_register(struct ccu_rate_reset_nb
> *rate_reset_nb);
> +
>  #endif /* _COMMON_H_ */
>