linux-kernel - Re: [PATCH v3 1/5] clk: sunxi-ng: common: Support minimum and maximum rate

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Date: Mon, 4 Mar 2024 11:06:38 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Frank Oltmanns <frank@...manns.dev>
Cc: Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Guido Günther <agx@...xcpu.org>, Purism Kernel Team <kernel@...i.sm>, Ondrej Jirman <megi@....cz>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sam Ravnborg <sam@...nborg.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, linux-clk@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v3 1/5] clk: sunxi-ng: common: Support minimum and
 maximum rate

On Mon, Mar 04, 2024 at 08:29:17AM +0100, Frank Oltmanns wrote:
> The Allwinner SoC's typically have an upper and lower limit for their
> clocks' rates. Up until now, support for that has been implemented
> separately for each clock type.
> 
> Implement that functionality in the sunxi-ng's common part making use of
> the CCF rate liming capabilities, so that it is available for all clock
> types.
> 
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> Cc: stable@...r.kernel.org
> ---
>  drivers/clk/sunxi-ng/ccu_common.c | 15 +++++++++++++++
>  drivers/clk/sunxi-ng/ccu_common.h |  3 +++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_common.c b/drivers/clk/sunxi-ng/ccu_common.c
> index 8babce55302f..2152063eee16 100644
> --- a/drivers/clk/sunxi-ng/ccu_common.c
> +++ b/drivers/clk/sunxi-ng/ccu_common.c
> @@ -44,6 +44,12 @@ bool ccu_is_better_rate(struct ccu_common *common,
>  			unsigned long current_rate,
>  			unsigned long best_rate)
>  {
> +	if (common->max_rate && current_rate > common->max_rate)
> +		return false;
> +
> +	if (common->min_rate && current_rate < common->min_rate)
> +		return false;
> +

We should use clk_hw_get_rate_range() here, there might be some
additional constraints to the rate range than the hardware ones (ie,
calls to clk_set_rate_range()).

>  	if (common->features & CCU_FEATURE_CLOSEST_RATE)
>  		return abs(current_rate - target_rate) < abs(best_rate - target_rate);
>  
> @@ -122,7 +128,10 @@ static int sunxi_ccu_probe(struct sunxi_ccu *ccu, struct device *dev,
>  
>  	for (i = 0; i < desc->hw_clks->num ; i++) {
>  		struct clk_hw *hw = desc->hw_clks->hws[i];
> +		struct ccu_common *common = hw_to_ccu_common(hw);
>  		const char *name;
> +		unsigned long min_rate = 0;
> +		unsigned long max_rate = ULONG_MAX;
>  
>  		if (!hw)
>  			continue;
> @@ -136,6 +145,12 @@ static int sunxi_ccu_probe(struct sunxi_ccu *ccu, struct device *dev,
>  			pr_err("Couldn't register clock %d - %s\n", i, name);
>  			goto err_clk_unreg;
>  		}
> +
> +		if (common->min_rate)
> +			min_rate = common->min_rate;
> +		if (common->max_rate)
> +			max_rate = common->max_rate;

max_rate should always be set to ULONG_MAX. I would drop the tests for
both here, and warn if max_rate is set to 0.

Maxime

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