Re: [PATCH v2 2/4] clk: imx: add fractional PLL output clock

[Shawn Guo <shawnguo@kernel.org>]

On Thu, Feb 01, 2018 at 06:54:10PM +0100, Lucas Stach wrote:
> This is a new clock type introduced on i.MX8.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/clk/imx/Makefile       |   1 +
>  drivers/clk/imx/clk-frac-pll.c | 229 +++++++++++++++++++++++++++++++++++++++++
>  drivers/clk/imx/clk.h          |   3 +
>  3 files changed, 233 insertions(+)
>  create mode 100644 drivers/clk/imx/clk-frac-pll.c
> 
> diff --git a/drivers/clk/imx/Makefile b/drivers/clk/imx/Makefile
> index f91f2b2e11cd..9892ae63539c 100644
> --- a/drivers/clk/imx/Makefile
> +++ b/drivers/clk/imx/Makefile
> @@ -6,6 +6,7 @@ obj-y += \
>  	clk-cpu.o \
>  	clk-fixup-div.o \
>  	clk-fixup-mux.o \
> +	clk-frac-pll.o \
>  	clk-gate-exclusive.o \
>  	clk-gate2.o \
>  	clk-pllv1.o \
> diff --git a/drivers/clk/imx/clk-frac-pll.c b/drivers/clk/imx/clk-frac-pll.c
> new file mode 100644
> index 000000000000..30736d53dfbe
> --- /dev/null
> +++ b/drivers/clk/imx/clk-frac-pll.c
> @@ -0,0 +1,229 @@
> +/*
> + * Copyright 2017 NXP.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html

The SPDX tag is being used for include/dt-bindings/clock/imx8mq-clock.h.
It may be good for all clock driver new files as well?

> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/slab.h>
> +#include <linux/jiffies.h>

Sort them alphabetically?

> +
> +#include "clk.h"
> +
> +#define PLL_CFG0 	0x0
> +#define PLL_CFG1	0x4
> +
> +#define PLL_LOCK_STATUS	(0x1 << 31)
> +#define PLL_CLKE	21

Unused define?

> +#define PLL_PD		19
> +#define PLL_BYPASS	14
> +#define PLL_NEWDIV_VAL		(1 << 12)
> +#define PLL_NEWDIV_ACK		(1 << 11)

0x1 in PLL_LOCK_STATUS and 1 here lack consistency.  Maybe BIT() even
better?

> +#define PLL_FRAC_DIV_MASK	0xffffff
> +#define PLL_INT_DIV_MASK	0x7f
> +#define PLL_FRAC_DENOM		0x1000000

Can we make the indentation of all these defines consistent?

> +
> +struct clk_frac_pll {
> +	struct clk_hw	hw;
> +	void __iomem	*base;
> +};
> +
> +#define to_clk_frac_pll(_hw) container_of(_hw, struct clk_frac_pll, hw)
> +
> +static int clk_wait_lock(struct clk_frac_pll *pll)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(10);
> +
> +	/* Wait for PLL to lock */
> +	do {
> +		if (readl_relaxed(pll->base) & PLL_LOCK_STATUS)
> +			break;
> +		if (time_after(jiffies, timeout))
> +			break;
> +	} while (1);
> +
> +	return readl_relaxed(pll->base) & PLL_LOCK_STATUS ? 0 : -ETIMEDOUT;
> +}
> +
> +static int clk_wait_ack(struct clk_frac_pll *pll)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(50);
> +
> +	/* return directly if the pll is in powerdown or in bypass */
> +	if (readl_relaxed(pll->base) & ((1 << PLL_PD) | (1 << PLL_BYPASS)))

Instead of bit shift, it seems that defining PLL_PD and PLL_BYPASS as
bit mask will make the code a bit simpler.

> +		return 0;
> +
> +	/* Wait for the pll's divfi and divff to be reloaded */
> +	do {
> +		if (readl_relaxed(pll->base) & PLL_NEWDIV_ACK)
> +			break;
> +		if (time_after(jiffies, timeout))
> +			break;
> +	} while (1);
> +
> +	return readl_relaxed(pll->base) & PLL_NEWDIV_ACK ? 0 : ETIMEDOUT;
> +}
> +
> +static int clk_pll_prepare(struct clk_hw *hw)
> +{
> +	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
> +	u32 val;
> +
> +	val = readl_relaxed(pll->base + PLL_CFG0);
> +	val &= ~(1 << PLL_PD);
> +	writel_relaxed(val, pll->base + PLL_CFG0);
> +
> +	return clk_wait_lock(pll);
> +}
> +
> +static void clk_pll_unprepare(struct clk_hw *hw)
> +{
> +	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
> +	u32 val;
> +
> +	val = readl_relaxed(pll->base + PLL_CFG0);
> +	val |= (1 << PLL_PD);
> +	writel_relaxed(val, pll->base + PLL_CFG0);
> +}
> +
> +static int clk_pll_is_prepared(struct clk_hw *hw)
> +{
> +	struct clk_frac_pll *pll = to_clk_frac_pll(hw);
> +	u32 val;
> +
> +	val = readl_relaxed(pll->base + PLL_CFG0);
> +	return (val & (1 << PLL_PD)) ? 0 : 1;
> +}
> +
> +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 & 0x1f) + 1) * 2;
> +	val = readl_relaxed(pll->base + PLL_CFG1);
> +	divff = (val >> 7) & PLL_FRAC_DIV_MASK;
> +	divfi = (val & PLL_INT_DIV_MASK);
> +
> +	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)
> +{
> +	u32 divff, divfi;
> +	u64 temp64;
> +	unsigned long parent_rate = *prate;
> +
> +	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;
> +
> +	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 << 7) | (PLL_INT_DIV_MASK));
> +	val |= ((divff << 7) | (divfi - 1));

	val |= (divff << 7) | (divfi - 1);

Shawn

> +	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_frac_pll *pll;
> +	struct clk *clk;
> +	struct clk_init_data init;
> +
> +	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);
> +	if (IS_ERR(clk))
> +		kfree(pll);
> +
> +	return clk;
> +}
> diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
> index d69c4bbf3597..287610902ea8 100644
> --- a/drivers/clk/imx/clk.h
> +++ b/drivers/clk/imx/clk.h
> @@ -27,6 +27,9 @@ struct clk *imx_clk_pllv1(enum imx_pllv1_type type, const char *name,
>  struct clk *imx_clk_pllv2(const char *name, const char *parent,
>  		void __iomem *base);
>  
> +struct clk *imx_clk_frac_pll(const char *name, const char *parent_name,
> +			     void __iomem *base);
> +
>  enum imx_pllv3_type {
>  	IMX_PLLV3_GENERIC,
>  	IMX_PLLV3_SYS,
> -- 
> 2.15.1
>