linux-kernel - Re: [PATCH v5 05/11] clk: sunxi-ng: Add helper function to find closest rate

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Message-ID: <8292789.NyiUUSuA9g@jernej-laptop>
Date:   Sun, 06 Aug 2023 15:41:48 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Maxime Ripard <mripard@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Andre Przywara <andre.przywara@....com>,
        Roman Beranek <me@...y.cz>, Frank Oltmanns <frank@...manns.dev>
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Frank Oltmanns <frank@...manns.dev>
Subject: Re: [PATCH v5 05/11] clk: sunxi-ng: Add helper function to find closest rate

Dne nedelja, 06. avgust 2023 ob 15:06:50 CEST je Frank Oltmanns napisal(a):
> The default behaviour of clocks in the sunxi-ng driver is to select a
> clock rate that is closest to but less than the requested rate.
> 
> Add the ccu_is_better_rate() helper function that - depending on the
> fact if thc CCU_FEATURE_CLOSEST_RATE flag is set - decides if a rate is
> closer than another rate.
> 
> Acked-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>

Reviewed-by: Jernej Skrabec <jernej.skrabec@...il.com>

Best regards,
Jernej

> ---
>  drivers/clk/sunxi-ng/ccu_common.c | 12 ++++++++++++
>  drivers/clk/sunxi-ng/ccu_common.h |  5 +++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_common.c
> b/drivers/clk/sunxi-ng/ccu_common.c index 8d28a7a079d0..8babce55302f 100644
> --- a/drivers/clk/sunxi-ng/ccu_common.c
> +++ b/drivers/clk/sunxi-ng/ccu_common.c
> @@ -39,6 +39,18 @@ void ccu_helper_wait_for_lock(struct ccu_common *common,
> u32 lock) }
>  EXPORT_SYMBOL_NS_GPL(ccu_helper_wait_for_lock, SUNXI_CCU);
> 
> +bool ccu_is_better_rate(struct ccu_common *common,
> +			unsigned long target_rate,
> +			unsigned long current_rate,
> +			unsigned long best_rate)
> +{
> +	if (common->features & CCU_FEATURE_CLOSEST_RATE)
> +		return abs(current_rate - target_rate) < abs(best_rate - 
target_rate);
> +
> +	return current_rate <= target_rate && current_rate > best_rate;
> +}
> +EXPORT_SYMBOL_NS_GPL(ccu_is_better_rate, SUNXI_CCU);
> +
>  /*
>   * This clock notifier is called when the frequency of a PLL clock is
>   * changed. In common PLL designs, changes to the dividers take effect
> diff --git a/drivers/clk/sunxi-ng/ccu_common.h
> b/drivers/clk/sunxi-ng/ccu_common.h index 5ad219f041d5..942a72c09437 100644
> --- a/drivers/clk/sunxi-ng/ccu_common.h
> +++ b/drivers/clk/sunxi-ng/ccu_common.h
> @@ -53,6 +53,11 @@ struct sunxi_ccu_desc {
> 
>  void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock);
> 
> +bool ccu_is_better_rate(struct ccu_common *common,
> +			unsigned long target_rate,
> +			unsigned long current_rate,
> +			unsigned long best_rate);
> +
>  struct ccu_pll_nb {
>  	struct notifier_block	clk_nb;
>  	struct ccu_common	*common;