Re: [RFC 2/2] mux: mmio-based syscon mux controller

[Steve Longerbeam]

On 04/13/2017 08:48 AM, Philipp Zabel wrote:
> This adds a driver for mmio-based syscon multiplexers controlled by a
> single bitfield in a syscon register range.
>
> Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> ---
>   drivers/mux/Kconfig      |  13 +++++
>   drivers/mux/Makefile     |   1 +
>   drivers/mux/mux-syscon.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 144 insertions(+)
>   create mode 100644 drivers/mux/mux-syscon.c
>
> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> index 86668b4d2fc52..a5e6a3b01ac24 100644
> --- a/drivers/mux/Kconfig
> +++ b/drivers/mux/Kconfig
> @@ -43,4 +43,17 @@ config MUX_GPIO
>   	  To compile the driver as a module, choose M here: the module will
>   	  be called mux-gpio.
>   
> +config MUX_SYSCON

my preference would be CONFIG_MUX_MMIO.

> +	tristate "MMIO bitfield-controlled Multiplexer"

"MMIO register bitfield-controlled Multiplexer"

The rest looks good to me.

Steve

> +	depends on OF && MFD_SYSCON
> +	help
> +	  MMIO bitfield-controlled Multiplexer controller.
> +
> +	  The driver builds a single multiplexer controller using a bitfield
> +	  in a syscon register. For N bit wide bitfields, there will be 2^N
> +	  possible multiplexer states.
> +
> +	  To compile the driver as a module, choose M here: the module will
> +	  be called mux-syscon.
> +
>   endif
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index b00a7d37d2fbe..234309f6655f7 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -5,3 +5,4 @@
>   obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
>   obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
>   obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
> +obj-$(CONFIG_MUX_SYSCON)	+= mux-syscon.o
> diff --git a/drivers/mux/mux-syscon.c b/drivers/mux/mux-syscon.c
> new file mode 100644
> index 0000000000000..31cacc61f1439
> --- /dev/null
> +++ b/drivers/mux/mux-syscon.c
> @@ -0,0 +1,130 @@
> +/*
> + * syscon bitfield-controlled multiplexer driver
> + *
> + * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@xxxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/mux.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +struct mux_syscon {
> +	struct regmap_field *field;
> +};
> +
> +static int mux_syscon_set(struct mux_control *mux, int state)
> +{
> +	struct mux_syscon *mux_syscon = mux_chip_priv(mux->chip);
> +
> +	return regmap_field_write(mux_syscon->field, state);
> +}
> +
> +static const struct mux_control_ops mux_syscon_ops = {
> +	.set = mux_syscon_set,
> +};
> +
> +static const struct of_device_id mux_syscon_dt_ids[] = {
> +	{ .compatible = "mmio-mux", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mux_syscon_dt_ids);
> +
> +static int of_get_reg_field(struct device_node *node, struct reg_field *field)
> +{
> +	u32 bit_mask;
> +	int ret;
> +
> +	ret = of_property_read_u32(node, "reg", &field->reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = of_property_read_u32(node, "bit-mask", &bit_mask);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = of_property_read_u32(node, "bit-shift", &field->lsb);
> +	if (ret < 0)
> +		return ret;
> +
> +	field->msb = field->lsb + fls(bit_mask) - 1;
> +
> +	return 0;
> +}
> +
> +static int mux_syscon_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mux_chip *mux_chip;
> +	struct mux_syscon *mux_syscon;
> +	struct regmap *regmap;
> +	struct reg_field field;
> +	int bits;
> +	s32 idle_state;
> +	int ret;
> +
> +	ret = of_get_reg_field(pdev->dev.of_node, &field);
> +	if (ret) {
> +		dev_err(&pdev->dev, "missing bit-field properties: %d\n", ret);
> +		return ret;
> +	}
> +
> +	regmap = syscon_node_to_regmap(pdev->dev.of_node->parent);
> +	if (IS_ERR(regmap)) {
> +		ret = PTR_ERR(regmap);
> +		dev_err(&pdev->dev, "failed to get syscon regmap: %d\n", ret);
> +		return ret;
> +	}
> +
> +	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux_syscon));
> +	if (!mux_chip)
> +		return -ENOMEM;
> +
> +	mux_syscon = mux_chip_priv(mux_chip);
> +	mux_chip->ops = &mux_syscon_ops;
> +
> +	mux_syscon->field = devm_regmap_field_alloc(&pdev->dev, regmap, field);
> +	if (IS_ERR(mux_syscon->field)) {
> +		ret = PTR_ERR(mux_syscon->field);
> +		dev_err(&pdev->dev, "failed to regmap bit-field: %d\n", ret);
> +		return ret;
> +	}
> +	bits = 1 + field.msb - field.lsb;
> +
> +	mux_chip->mux->states = 1 << bits;
> +
> +	ret = device_property_read_u32(dev, "idle-state", (u32 *)&idle_state);
> +	if (ret >= 0 && idle_state != MUX_IDLE_AS_IS) {
> +		if (idle_state < 0 || idle_state >= mux_chip->mux->states) {
> +			dev_err(dev, "invalid idle-state %u\n", idle_state);
> +			return -EINVAL;
> +		}
> +
> +		mux_chip->mux->idle_state = idle_state;
> +	}
> +
> +	regmap_field_read(mux_syscon->field, &mux_chip->mux->cached_state);
> +
> +	return devm_mux_chip_register(dev, mux_chip);
> +}
> +
> +static struct platform_driver mux_syscon_driver = {
> +	.driver = {
> +		.name = "mmio-mux",
> +		.of_match_table	= of_match_ptr(mux_syscon_dt_ids),
> +	},
> +	.probe = mux_syscon_probe,
> +};
> +module_platform_driver(mux_syscon_driver);
> +
> +MODULE_DESCRIPTION("MMIO bitfield-controlled multiplexer driver");
> +MODULE_AUTHOR("Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");