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From: Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To: Michael Turquette <mturquette@baylibre.com>,
 Stephen Boyd <sboyd@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
 Samuel Holland <samuel@sholland.org>,
 Guido =?ISO-8859-1?Q?G=FCnther?= <agx@sigxcpu.org>,
 Purism Kernel Team <kernel@puri.sm>, Ondrej Jirman <megi@xff.cz>,
 Neil Armstrong <neil.armstrong@linaro.org>,
 Jessica Zhang <quic_jesszhan@quicinc.com>, Sam Ravnborg <sam@ravnborg.org>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 Frank Oltmanns <frank@oltmanns.dev>
Cc: linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
 dri-devel@lists.freedesktop.org, Frank Oltmanns <frank@oltmanns.dev>
Subject:
 Re: [PATCH 1/5] clk: sunxi-ng: nkm: Support constraints on m/n ratio and
 parent rate
Date: Tue, 19 Dec 2023 17:46:08 +0100
Message-ID: <5736273.DvuYhMxLoT@jernej-laptop>
In-Reply-To: <20231218-pinephone-pll-fixes-v1-1-e238b6ed6dc1@oltmanns.dev>
References:
 <20231218-pinephone-pll-fixes-v1-0-e238b6ed6dc1@oltmanns.dev>
 <20231218-pinephone-pll-fixes-v1-1-e238b6ed6dc1@oltmanns.dev>
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Hi Frank!

Dne ponedeljek, 18. december 2023 ob 14:35:19 CET je Frank Oltmanns napisal(a):
> The Allwinner A64 manual lists the following constraints for the
> PLL-MIPI clock:
>  - M/N >= 3

This should be "<="

>  - (PLL_VIDEO0)/M >= 24MHz
> 
> The PLL-MIPI clock is implemented as ccu_nkm. Therefore, add support for
> these constraints.
> 
> Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
> ---
>  drivers/clk/sunxi-ng/ccu_nkm.c | 23 +++++++++++++++++++++++
>  drivers/clk/sunxi-ng/ccu_nkm.h |  8 ++++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> index eed64547ad42..2af5c1ebd527 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> @@ -16,6 +16,20 @@ struct _ccu_nkm {
>  	unsigned long	m, min_m, max_m;
>  };
>  
> +static bool ccu_nkm_is_valid_rate(struct ccu_common *common, unsigned long parent,
> +				  unsigned long n, unsigned long m)
> +{
> +	struct ccu_nkm *nkm = container_of(common, struct ccu_nkm, common);
> +
> +	if (nkm->max_mn_ratio && (m > nkm->max_mn_ratio * n))
> +		return false;
> +
> +	if (nkm->parent_wo_nk && (parent < nkm->parent_wo_nk * m))
> +		return false;
> +
> +	return true;
> +}
> +
>  static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common,
>  						       struct clk_hw *parent_hw,
>  						       unsigned long *parent, unsigned long rate,
> @@ -32,6 +46,9 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common
>  
>  				tmp_parent = clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));
>  
> +				if (!ccu_nkm_is_valid_rate(common, tmp_parent, _n, _m))
> +					continue;
> +
>  				tmp_rate = tmp_parent * _n * _k / _m;
>  
>  				if (ccu_is_better_rate(common, rate, tmp_rate, best_rate) ||
> @@ -65,6 +82,12 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
>  	for (_k = nkm->min_k; _k <= nkm->max_k; _k++) {
>  		for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
>  			for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
> +				if ((common->reg == 0x040) && (_m > 3 * _n))
> +					break;
> +
> +				if ((common->reg == 0x040) && (parent < 24000000 * _m))
> +					continue;
> +

You already figured this part.

>  				unsigned long tmp_rate;
>  
>  				tmp_rate = parent * _n * _k / _m;
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
> index 6601defb3f38..d3d3eaf55faf 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.h
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.h
> @@ -16,6 +16,12 @@
>   * struct ccu_nkm - Definition of an N-K-M clock
>   *
>   * Clocks based on the formula parent * N * K / M
> + *
> + * @max_mn_ratio:	Maximum value for M / N.
> + * @parent_wo_nk:	The minimum rate the parent must provide after applying the divisor,
> + *			but without applying the multipliers, i.e. the contstraint
> + *			   (parent rate)/M >= parent_wo_nk
> + *			must be fulfilled.
>   */
>  struct ccu_nkm {
>  	u32			enable;
> @@ -27,6 +33,8 @@ struct ccu_nkm {
>  	struct ccu_mux_internal	mux;
>  
>  	unsigned int		fixed_post_div;
> +	unsigned long		max_mn_ratio;
> +	unsigned long           parent_wo_nk;

What about max_m_n_ratio and max_parent_m_ratio, to be consistent? This
should also allow to simplify description.

Best regards,
Jernej

>  
>  	struct ccu_common	common;
>  };
> 
>