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Message-ID: <58fd5844-f24a-37cc-be81-26a716251860@gmail.com>
Date: Thu, 13 Apr 2017 18:09:50 -0700
From: Steve Longerbeam <slongerbeam@...il.com>
To: Philipp Zabel <p.zabel@...gutronix.de>,
Peter Rosin <peda@...ntia.se>
Cc: Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Sakari Ailus <sakari.ailus@....fi>, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [RFC 2/2] mux: mmio-based syscon mux controller
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@...gutronix.de>
> ---
> 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@...gutronix.de>
> + *
> + * 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@...gutronix.de>");
> +MODULE_LICENSE("GPL v2");
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