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Message-ID: <153980638471.5275.2935268205764106887@swboyd.mtv.corp.google.com>
Date: Wed, 17 Oct 2018 12:59:44 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Abel Vesa <abel.vesa@....com>,
Andrey Smirnov <andrew.smirnov@...il.com>,
Anson Huang <anson.huang@....com>,
Dong Aisheng <aisheng.dong@....com>,
Fabio Estevam <fabio.estevam@....com>,
Lucas Stach <l.stach@...gutronix.de>,
Rob Herring <robh@...nel.org>,
Sascha Hauer <kernel@...gutronix.de>
Cc: linux-imx@....com, Abel Vesa <abelvesa@...ux.com>,
Abel Vesa <abel.vesa@....com>, Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Michael Turquette <mturquette@...libre.com>,
open list <linux-kernel@...r.kernel.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>,
"open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v9 2/5] clk: imx: add fractional PLL output clock
Quoting Abel Vesa (2018-09-24 03:39:54)
> From: Lucas Stach <l.stach@...gutronix.de>
>
> This is a new clock type introduced on i.MX8.
Ok, what's the clock type? Add another sentence please.
>
> Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
> Signed-off-by: Abel Vesa <abel.vesa@....com>
[..]
> diff --git a/drivers/clk/imx/clk-frac-pll.c b/drivers/clk/imx/clk-frac-pll.c
> new file mode 100644
> index 0000000..030df76
> --- /dev/null
> +++ b/drivers/clk/imx/clk-frac-pll.c
> @@ -0,0 +1,215 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2018 NXP.
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/jiffies.h>
Is this used for something?
> +#include <linux/slab.h>
> +#include <linux/bitfield.h>
> +
> +#include "clk.h"
[...]
> +
> +static unsigned long clk_pll_recalc_rate(struct clk_hw *hw,
> + unsigned long parent_rate)
> +{
> + struct clk_frac_pll *pll = to_clk_frac_pll(hw);
> + u32 val, divff, divfi, divq;
> + u64 temp64;
> +
> + val = readl_relaxed(pll->base + PLL_CFG0);
> + divq = ((val & PLL_OUTPUT_DIV_MASK) + 1) * 2;
> + val = readl_relaxed(pll->base + PLL_CFG1);
> + divff = FIELD_GET(PLL_FRAC_DIV_MASK, val);
> + divfi = (val & PLL_INT_DIV_MASK);
Nitpick: Drop useless parenthesis please.
> +
> + temp64 = (u64)parent_rate * 8;
> + temp64 *= divff;
> + do_div(temp64, PLL_FRAC_DENOM);
> + temp64 /= divq;
> +
> + return parent_rate * 8 * (divfi + 1) / divq + (unsigned long)temp64;
> +}
> +
> +static long clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long *prate)
> +{
> + unsigned long parent_rate = *prate;
> + u32 divff, divfi;
> + u64 temp64;
> +
> + parent_rate *= 8;
And parent_rate can't overflow if it's a u32? Maybe it could be a u64 so
that we don't need casting later on in this function.
> + rate *= 2;
> + divfi = rate / parent_rate;
> + temp64 = (u64)(rate - divfi * parent_rate);
> + temp64 *= PLL_FRAC_DENOM;
> + do_div(temp64, parent_rate);
> + divff = temp64;
> +
> + temp64 = (u64)parent_rate;
> + temp64 *= divff;
> + do_div(temp64, PLL_FRAC_DENOM);
> +
> + return (parent_rate * divfi + (unsigned long)temp64) / 2;
> +}
> +
> +/*
> + * To simplify the clock calculation, we can keep the 'PLL_OUTPUT_VAL' at zero
> + * (means the PLL output will be divided by 2). So the PLL output can use
> + * the below formula:
> + * pllout = parent_rate * 8 / 2 * DIVF_VAL;
> + * where DIVF_VAL = 1 + DIVFI + DIVFF / 2^24.
> + */
> +static int clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + struct clk_frac_pll *pll = to_clk_frac_pll(hw);
> + u32 val, divfi, divff;
> + u64 temp64;
> + int ret;
> +
> + parent_rate *= 8;
> + rate *= 2;
> + divfi = rate / parent_rate;
> + temp64 = (u64) (rate - divfi * parent_rate);
> + temp64 *= PLL_FRAC_DENOM;
> + do_div(temp64, parent_rate);
> + divff = temp64;
> +
> + val = readl_relaxed(pll->base + PLL_CFG1);
> + val &= ~(PLL_FRAC_DIV_MASK | PLL_INT_DIV_MASK);
> + val |= ((divff << 7) | (divfi - 1));
Nitpick: Drop the extra parenthesis please.
> + writel_relaxed(val, pll->base + PLL_CFG1);
> +
> + val = readl_relaxed(pll->base + PLL_CFG0);
> + val &= ~0x1f;
> + writel_relaxed(val, pll->base + PLL_CFG0);
> +
> + /* Set the NEV_DIV_VAL to reload the DIVFI and DIVFF */
> + val = readl_relaxed(pll->base + PLL_CFG0);
> + val |= PLL_NEWDIV_VAL;
> + writel_relaxed(val, pll->base + PLL_CFG0);
> +
> + ret = clk_wait_ack(pll);
> +
> + /* clear the NEV_DIV_VAL */
> + val = readl_relaxed(pll->base + PLL_CFG0);
> + val &= ~PLL_NEWDIV_VAL;
> + writel_relaxed(val, pll->base + PLL_CFG0);
> +
> + return ret;
> +}
> +
> +static const struct clk_ops clk_frac_pll_ops = {
> + .prepare = clk_pll_prepare,
> + .unprepare = clk_pll_unprepare,
> + .is_prepared = clk_pll_is_prepared,
> + .recalc_rate = clk_pll_recalc_rate,
> + .round_rate = clk_pll_round_rate,
> + .set_rate = clk_pll_set_rate,
> +};
> +
> +struct clk *imx_clk_frac_pll(const char *name, const char *parent_name,
> + void __iomem *base)
> +{
> + struct clk_init_data init;
> + struct clk_frac_pll *pll;
> + struct clk *clk;
> +
> + pll = kzalloc(sizeof(*pll), GFP_KERNEL);
> + if (!pll)
> + return ERR_PTR(-ENOMEM);
> +
> + pll->base = base;
> + init.name = name;
> + init.ops = &clk_frac_pll_ops;
> + init.flags = 0;
> + init.parent_names = &parent_name;
> + init.num_parents = 1;
> +
> + pll->hw.init = &init;
> +
> + clk = clk_register(NULL, &pll->hw);
clk_hw based please.
> + if (IS_ERR(clk))
> + kfree(pll);
> +
> + return clk;
> +}
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