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References: <20240205-pinephone-pll-fixes-v2-0-96a46a2d8c9b@oltmanns.dev>
 <20240205-pinephone-pll-fixes-v2-1-96a46a2d8c9b@oltmanns.dev>
 <2717565.mvXUDI8C0e@jernej-laptop>
From: Frank Oltmanns <frank@oltmanns.dev>
To: Jernej =?utf-8?Q?=C5=A0krabec?= <jernej.skrabec@gmail.com>
Cc: Michael Turquette <mturquette@baylibre.com>, Stephen Boyd
 <sboyd@kernel.org>, Chen-Yu Tsai <wens@csie.org>, Samuel Holland
 <samuel@sholland.org>, Guido =?utf-8?Q?G=C3=BCnther?= <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>, Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley
 <conor+dt@kernel.org>, 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,
 devicetree@vger.kernel.org
Subject: Re: [PATCH v2 1/6] clk: sunxi-ng: nkm: Support constraints on m/n
 ratio and parent rate
In-reply-to: <2717565.mvXUDI8C0e@jernej-laptop>
Date: Mon, 05 Feb 2024 18:50:27 +0100
Message-ID: <87il32ztp8.fsf@oltmanns.dev>
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Hi Jernej,

On 2024-02-05 at 18:45:27 +0100, Jernej =C5=A0krabec <jernej.skrabec@gmail.=
com> wrote:
> Dne ponedeljek, 05. februar 2024 ob 16:22:24 CET je Frank Oltmanns napisa=
l(a):
>> The Allwinner A64 manual lists the following constraints for the
>> PLL-MIPI clock:
>>  - M/N <=3D 3
>>  - (PLL_VIDEO0)/M >=3D 24MHz
>>
>> The PLL-MIPI clock is implemented as ccu_nkm. Therefore, add support for
>> these constraints.
>>
>> Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
>
> Haven't we discussed that this patch is unnecessary because same effect c=
an
> be reached by limiting minimum frequency?

The patch for ccu_nm was unnecessary:
https://lore.kernel.org/all/87jzoug2jz.fsf@oltmanns.dev/

Unfortunately, we still need this one.

Best regards,
  Frank

>
> Best regards,
> Jernej
>
>> ---
>>  drivers/clk/sunxi-ng/ccu_nkm.c | 21 +++++++++++++++++++++
>>  drivers/clk/sunxi-ng/ccu_nkm.h |  2 ++
>>  2 files changed, 23 insertions(+)
>>
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_n=
km.c
>> index 853f84398e2b..1168d894d636 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 l=
ong parent,
>> +				  unsigned long n, unsigned long m)
>> +{
>> +	struct ccu_nkm *nkm =3D container_of(common, struct ccu_nkm, common);
>> +
>> +	if (nkm->max_m_n_ratio && (m > nkm->max_m_n_ratio * n))
>> +		return false;
>> +
>> +	if (nkm->min_parent_m_ratio && (parent < nkm->min_parent_m_ratio * m))
>> +		return false;
>> +
>> +	return true;
>> +}
>> +
>>  static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_commo=
n *common,
>>  						       struct clk_hw *parent_hw,
>>  						       unsigned long *parent, unsigned long rate,
>> @@ -31,6 +45,10 @@ static unsigned long ccu_nkm_find_best_with_parent_ad=
j(struct ccu_common *common
>>  				unsigned long tmp_rate, tmp_parent;
>>
>>  				tmp_parent =3D clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));
>> +
>> +				if (!ccu_nkm_is_valid_rate(common, tmp_parent, _n, _m))
>> +					continue;
>> +
>>  				tmp_rate =3D tmp_parent * _n * _k / _m;
>>
>>  				if (ccu_is_better_rate(common, rate, tmp_rate, best_rate) ||
>> @@ -64,6 +82,9 @@ static unsigned long ccu_nkm_find_best(unsigned long p=
arent, unsigned long rate,
>>  	for (_k =3D nkm->min_k; _k <=3D nkm->max_k; _k++) {
>>  		for (_n =3D nkm->min_n; _n <=3D nkm->max_n; _n++) {
>>  			for (_m =3D nkm->min_m; _m <=3D nkm->max_m; _m++) {
>> +				if (!ccu_nkm_is_valid_rate(common, parent, _n, _m))
>> +					continue;
>> +
>>  				unsigned long tmp_rate;
>>
>>  				tmp_rate =3D parent * _n * _k / _m;
>> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_n=
km.h
>> index 6601defb3f38..c409212ee40e 100644
>> --- a/drivers/clk/sunxi-ng/ccu_nkm.h
>> +++ b/drivers/clk/sunxi-ng/ccu_nkm.h
>> @@ -27,6 +27,8 @@ struct ccu_nkm {
>>  	struct ccu_mux_internal	mux;
>>
>>  	unsigned int		fixed_post_div;
>> +	unsigned long		max_m_n_ratio;
>> +	unsigned long		min_parent_m_ratio;
>>
>>  	struct ccu_common	common;
>>  };
>>
>>