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From: Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To: Frank Oltmanns <frank@oltmanns.dev>
Cc: 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>,
 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
Subject:
 Re: [PATCH 1/5] clk: sunxi-ng: nkm: Support constraints on m/n ratio and
 parent rate
Date: Wed, 20 Dec 2023 16:09:55 +0100
Message-ID: <23332183.6Emhk5qWAg@jernej-laptop>
In-Reply-To: <87msu59wrc.fsf@oltmanns.dev>
References:
 <20231218-pinephone-pll-fixes-v1-0-e238b6ed6dc1@oltmanns.dev>
 <5736273.DvuYhMxLoT@jernej-laptop> <87msu59wrc.fsf@oltmanns.dev>
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Dne sreda, 20. december 2023 ob 07:58:07 CET je Frank Oltmanns napisal(a):
> Hi Jernej!
>=20
> On 2023-12-19 at 17:46:08 +0100, Jernej =C5=A0krabec <jernej.skrabec@gmai=
l.com> wrote:
> > Hi Frank!
> >
> > Dne ponedeljek, 18. december 2023 ob 14:35:19 CET je Frank Oltmanns nap=
isal(a):
> >> The Allwinner A64 manual lists the following constraints for the
> >> PLL-MIPI clock:
> >>  - M/N >=3D 3
> >
> > This should be "<=3D"
>=20
> Yes, good catch! I will fix it in V2.
>=20
> >
> >>  - (PLL_VIDEO0)/M >=3D 24MHz
> >>
> >> The PLL-MIPI clock is implemented as ccu_nkm. Therefore, add support f=
or
> >> 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 =3D 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_com=
mon *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_a=
dj(struct ccu_common *common
> >>
> >>  				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) ||
> >> @@ -65,6 +82,12 @@ static unsigned long ccu_nkm_find_best(unsigned lon=
g parent, 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 ((common->reg =3D=3D 0x040) && (_m > 3 * _n))
> >> +					break;
> >> +
> >> +				if ((common->reg =3D=3D 0x040) && (parent < 24000000 * _m))
> >> +					continue;
> >> +
> >
> > You already figured this part.
> >
> >>  				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=
_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 appl=
ying the divisor,
> >> + *			but without applying the multipliers, i.e. the contstraint
> >> + *			   (parent rate)/M >=3D 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.
>=20
> Jernej, thank you so much! This is brilliant! I was racking my brain for
> a good name but failed. Now, that I see your proposal, I don't know why
> I hadn't come up with it. It's the obvious choice.
>=20
> I'd say with the new names we should be able to get rid of the comments
> describing the new struct members (also in ccu_nm.h). What are your
> thoughts on that?

Ah, I missed that only new ones are documented. Yeah, you can skip it.

Best regards,
Jernej

>=20
> Best regards,
>   Frank
>=20
> >
> > Best regards,
> > Jernej
> >
> >>
> >>  	struct ccu_common	common;
> >>  };
> >>
> >>
>=20