linux-kernel - Re: [PATCH v2 1/6] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate

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Message-ID: <2172947.irdbgypaU6@jernej-laptop>
Date: Tue, 06 Feb 2024 18:44:33 +0100
From: Jernej Škrabec <jernej.skrabec@...il.com>
To: Frank Oltmanns <frank@...manns.dev>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
 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>,
 Maxime Ripard <mripard@...nel.org>, 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
Subject:
 Re: [PATCH v2 1/6] clk: sunxi-ng: nkm: Support constraints on m/n ratio and
 parent rate

Dne ponedeljek, 05. februar 2024 ob 18:50:27 CET je Frank Oltmanns napisal(a):
> Hi Jernej,
> 
> On 2024-02-05 at 18:45:27 +0100, Jernej Škrabec <jernej.skrabec@...il.com> wrote:
> > Dne ponedeljek, 05. februar 2024 ob 16:22:24 CET je Frank Oltmanns napisal(a):
> >> The Allwinner A64 manual lists the following constraints for the
> >> PLL-MIPI clock:
> >>  - M/N <= 3
> >>  - (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@...manns.dev>
> >
> > Haven't we discussed that this patch is unnecessary because same effect can
> > 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.

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

Best regards,
Jernej

> 
> 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_nkm.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 long parent,
> >> +				  unsigned long n, unsigned long m)
> >> +{
> >> +	struct ccu_nkm *nkm = 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_common *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_adj(struct ccu_common *common
> >>  				unsigned long tmp_rate, tmp_parent;
> >>
> >>  				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) ||
> >> @@ -64,6 +82,9 @@ 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 (!ccu_nkm_is_valid_rate(common, parent, _n, _m))
> >> +					continue;
> >> +
> >>  				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..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;
> >>  };
> >>
> >>
>