linux-kernel - Re: [PATCH v2 3/6] clk: sunxi-ng: nkm: Support minimum and maximum rate

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Date: Mon, 05 Feb 2024 18:56:09 +0100
From: Jernej Škrabec <jernej.skrabec@...il.com>
To: 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>, Frank Oltmanns <frank@...manns.dev>
Cc: 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,
 Frank Oltmanns <frank@...manns.dev>
Subject:
 Re: [PATCH v2 3/6] clk: sunxi-ng: nkm: Support minimum and maximum rate

Dne ponedeljek, 05. februar 2024 ob 16:22:26 CET je Frank Oltmanns napisal(a):
> According to the Allwinner User Manual, the Allwinner A64 requires
> PLL-MIPI to run at 500MHz-1.4GHz. Add support for that to ccu_nkm.
> 
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> ---
>  drivers/clk/sunxi-ng/ccu_nkm.c | 13 +++++++++++++
>  drivers/clk/sunxi-ng/ccu_nkm.h |  2 ++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> index 1168d894d636..7d135908d6e0 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> @@ -181,6 +181,12 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
>  	if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
>  		rate *= nkm->fixed_post_div;
>  
> +	if (nkm->min_rate && rate < nkm->min_rate)
> +		rate = nkm->min_rate;
> +
> +	if (nkm->max_rate && rate > nkm->max_rate)
> +		rate = nkm->max_rate;

Please take a look at ccu_nm_round_rate() code. You need to consider postdiv
and you can return immediately.

> +
>  	if (!clk_hw_can_set_rate_parent(&nkm->common.hw))
>  		rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm, &nkm->common);
>  	else
> @@ -220,6 +226,13 @@ static int ccu_nkm_set_rate(struct clk_hw *hw, unsigned long rate,
>  	_nkm.min_m = 1;
>  	_nkm.max_m = nkm->m.max ?: 1 << nkm->m.width;
>  
> +
> +	if (nkm->min_rate && rate < nkm->min_rate)
> +		rate = nkm->min_rate;
> +
> +	if (nkm->max_rate && rate > nkm->max_rate)
> +		rate = nkm->max_rate;
> +

No need for this, clk subsystem calls round rate before setting actual clock
rate.

Best regards,
Jernej

>  	ccu_nkm_find_best(parent_rate, rate, &_nkm, &nkm->common);
>  
>  	spin_lock_irqsave(nkm->common.lock, flags);
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
> index c409212ee40e..358a9df6b6a0 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		min_rate;
> +	unsigned long		max_rate;
>  	unsigned long		max_m_n_ratio;
>  	unsigned long		min_parent_m_ratio;
>  
> 
>