Re: [PATCH v3] clk/axs10x: Add I2S PLL clock driver

[Vineet Gupta <Vineet.Gupta1@synopsys.com>]

On Thursday 31 March 2016 10:38 PM, Jose Abreu wrote:
> The ARC SDP I2S clock can be programmed using a
> specific PLL.
> 
> This patch has the goal of adding a clock driver
> that programs this PLL.
> 
> At this moment the rate values are hardcoded in
> a table but in the future it would be ideal to
> use a function which determines the PLL values
> given the desired rate.
> 
> Signed-off-by: Jose Abreu <joabreu@synopsys.com>
> ---
> 
> Changes v2 -> v3:
> * Implemented recalc_rate
> 
> Changes v1 -> v2:
> * Renamed folder to axs10x (as suggested by Alexey Brodkin)
> * Added more supported rates
> 
>  arch/arc/boot/dts/axs10x_mb.dtsi   |   5 ++
>  drivers/clk/Makefile               |   1 +
>  drivers/clk/axs10x/Makefile        |   1 +
>  drivers/clk/axs10x/i2s_pll_clock.c | 163 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 170 insertions(+)
>  create mode 100644 drivers/clk/axs10x/Makefile
>  create mode 100644 drivers/clk/axs10x/i2s_pll_clock.c
> 
> diff --git a/arch/arc/boot/dts/axs10x_mb.dtsi b/arch/arc/boot/dts/axs10x_mb.dtsi
> index ab5d570..9c68226 100644
> --- a/arch/arc/boot/dts/axs10x_mb.dtsi
> +++ b/arch/arc/boot/dts/axs10x_mb.dtsi
> @@ -23,6 +23,11 @@
>  				#clock-cells = <0>;
>  			};
>  
> +			i2sclk: i2sclk {
> +				compatible = "snps,i2s-pll-clock";
> +				#clock-cells = <0>;
> +			};
> +
>  			apbclk: apbclk {
>  				compatible = "fixed-clock";
>  				clock-frequency = <50000000>;
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index 46869d6..2ca62dc6 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -84,3 +84,4 @@ obj-$(CONFIG_X86)			+= x86/
>  obj-$(CONFIG_ARCH_ZX)			+= zte/
>  obj-$(CONFIG_ARCH_ZYNQ)			+= zynq/
>  obj-$(CONFIG_H8300)		+= h8300/
> +obj-$(CONFIG_ARC_PLAT_AXS10X)		+= axs10x/
> diff --git a/drivers/clk/axs10x/Makefile b/drivers/clk/axs10x/Makefile
> new file mode 100644
> index 0000000..01996b8
> --- /dev/null
> +++ b/drivers/clk/axs10x/Makefile
> @@ -0,0 +1 @@
> +obj-y += i2s_pll_clock.o
> diff --git a/drivers/clk/axs10x/i2s_pll_clock.c b/drivers/clk/axs10x/i2s_pll_clock.c
> new file mode 100644
> index 0000000..f050e70
> --- /dev/null
> +++ b/drivers/clk/axs10x/i2s_pll_clock.c
> @@ -0,0 +1,163 @@
> +/*
> + * Synopsys AXS10X SDP I2S PLL clock driver
> + *
> + * Copyright (C) 2016 Synopsys
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +#include <linux/clk-provider.h>
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +
> +/* FPGA Version Info */
> +#define FPGA_VER_INFO	0xE0011230
> +#define FPGA_VER_27M	0x000FBED9
> +
> +/* PLL registers addresses */
> +#define PLL_IDIV_ADDR	0xE00100A0
> +#define PLL_FBDIV_ADDR	0xE00100A4
> +#define PLL_ODIV0_ADDR	0xE00100A8
> +#define PLL_ODIV1_ADDR	0xE00100AC
> +
> +struct i2s_pll_cfg {
> +	unsigned int rate;
> +	unsigned int idiv;
> +	unsigned int fbdiv;
> +	unsigned int odiv0;
> +	unsigned int odiv1;
> +};
> +
> +static struct i2s_pll_cfg i2s_pll_cfg_27m[] = {
> +	/* 27 Mhz */
> +	{ 1024000, 0x104, 0x451, 0x10E38, 0x2000 },
> +	{ 1411200, 0x104, 0x596, 0x10D35, 0x2000 },
> +	{ 1536000, 0x208, 0xA28, 0x10B2C, 0x2000 },
> +	{ 2048000, 0x82, 0x451, 0x10E38, 0x2000 },
> +	{ 2822400, 0x82, 0x596, 0x10D35, 0x2000 },
> +	{ 3072000, 0x104, 0xA28, 0x10B2C, 0x2000 },
> +	{ 2116800, 0x82, 0x3CF, 0x10C30, 0x2000 },
> +	{ 2304000, 0x104, 0x79E, 0x10B2C, 0x2000 },
> +	{ 0, 0, 0, 0, 0 },
> +};
> +
> +static struct i2s_pll_cfg i2s_pll_cfg_28m[] = {
> +	/* 28.224 Mhz */
> +	{ 1024000, 0x82, 0x105, 0x107DF, 0x2000 },
> +	{ 1411200, 0x28A, 0x1, 0x10001, 0x2000 },
> +	{ 1536000, 0xA28, 0x187, 0x10042, 0x2000 },
> +	{ 2048000, 0x41, 0x105, 0x107DF, 0x2000 },
> +	{ 2822400, 0x145, 0x1, 0x10001, 0x2000 },
> +	{ 3072000, 0x514, 0x187, 0x10042, 0x2000 },
> +	{ 2116800, 0x514, 0x42, 0x10001, 0x2000 },
> +	{ 2304000, 0x619, 0x82, 0x10001, 0x2000 },
> +	{ 0, 0, 0, 0, 0 },
> +};
> +
> +struct i2s_pll_clk {
> +	struct clk_hw hw;
> +	unsigned long ref_clk;
> +	struct i2s_pll_cfg *pll_cfg;
> +};
> +
> +static inline struct i2s_pll_clk *to_i2s_pll_clk(struct clk_hw *hw)
> +{
> +	return container_of(hw, struct i2s_pll_clk, hw);
> +}

Abstraction is good, but do you really need this. I mean do you foresee future
changes where this implementation might change.

> +
> +static unsigned int i2s_pll_get_value(unsigned int val)
> +{
> +	return ((val & 0x3F) + ((val >> 6) & 0x3F));
> +}
> +
> +static unsigned long i2s_pll_recalc_rate(struct clk_hw *hw,
> +			unsigned long parent_rate)
> +{
> +	struct i2s_pll_clk *clk = to_i2s_pll_clk(hw);
> +	unsigned int idiv, fbdiv, odiv;
> +
> +	idiv = i2s_pll_get_value(readl((void *)PLL_IDIV_ADDR));
> +	fbdiv = i2s_pll_get_value(readl((void *)PLL_FBDIV_ADDR));
> +	odiv = i2s_pll_get_value(readl((void *)PLL_ODIV0_ADDR));

See comment below - you can probably use readl_relaxed()

> +
> +	return (((clk->ref_clk / idiv ) * fbdiv) / odiv);
> +}
> +
> +static long i2s_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> +			unsigned long *prate)
> +{
> +	/* TODO: Round rate to nearest valid rate */
> +	return rate;
> +}
> +
> +static int i2s_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> +			unsigned long parent_rate)
> +{
> +	struct i2s_pll_cfg *pll_cfg = to_i2s_pll_clk(hw)->pll_cfg;
> +	int i;
> +
> +	for (i = 0; pll_cfg[i].rate != 0; i++) {
> +		if (pll_cfg[i].rate == rate) {
> +			writel(pll_cfg[i].idiv, (void *)PLL_IDIV_ADDR);
> +			writel(pll_cfg[i].fbdiv, (void *)PLL_FBDIV_ADDR);
> +			writel(pll_cfg[i].odiv0, (void *)PLL_ODIV0_ADDR);
> +			writel(pll_cfg[i].odiv1, (void *)PLL_ODIV1_ADDR);

Note that there are writel_relaxed and readl_relaxed io accessors, which generate
better code, specially on ARC. If there is no strict ordering requirement for the
various PLL regs, you are safely use them.


> +			return 0;
> +		}
> +	}
> +
> +	pr_err("%s: invalid rate=%ld, parent_rate=%ld\n", __func__,
> +			rate, parent_rate);
> +	return -EINVAL;
> +}
> +
> +static const struct clk_ops i2s_pll_ops = {
> +	.recalc_rate = i2s_pll_recalc_rate,
> +	.round_rate = i2s_pll_round_rate,
> +	.set_rate = i2s_pll_set_rate,
> +};
> +
> +static void __init i2s_pll_clk_setup(struct device_node *node)
> +{
> +	const char *clk_name = node->name;
> +	struct clk *clk;
> +	struct i2s_pll_clk *pll_clk;
> +	struct clk_init_data init;
> +
> +	pll_clk = kzalloc(sizeof(*pll_clk), GFP_KERNEL);
> +	if (!pll_clk)
> +		return;
> +
> +	init.name = clk_name;
> +	init.ops = &i2s_pll_ops;
> +	init.flags = CLK_IS_BASIC;
> +	init.num_parents = 0;
> +	pll_clk->hw.init = &init;
> +
> +	clk = clk_register(NULL, &pll_clk->hw);
> +	if (IS_ERR(clk)) {
> +		pr_err("%s: failed to register %s div clock (%ld)\n",
> +				__func__, clk_name, PTR_ERR(clk));
> +		goto free_clock;
> +	}
> +
> +	if (readl((void *)FPGA_VER_INFO) <= FPGA_VER_27M) {

readl_relaxed ?


> +		pll_clk->ref_clk = 27000000;
> +		pll_clk->pll_cfg = i2s_pll_cfg_27m;
> +	} else {
> +		pll_clk->ref_clk = 28224000;
> +		pll_clk->pll_cfg = i2s_pll_cfg_28m;
> +	}
> +
> +	of_clk_add_provider(node, of_clk_src_simple_get, clk);
> +	return;
> +
> +free_clock:
> +	kfree(pll_clk);
> +}
> +
> +CLK_OF_DECLARE(i2s_pll_clk, "snps,i2s-pll-clock", i2s_pll_clk_setup);
> +
>