Date:   Mon, 18 Feb 2019 09:47:12 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Pankaj Bansal <pankaj.bansal@....com>, Leo Li <leoyang.li@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>
Subject: Re: [PATCH] drivers: mux: Generic register bitfield-based multiplexer
 driver

Hi!

On 2019-02-18 06:40, Pankaj Bansal wrote:
> Generic register bitfield-based multiplexer driver that controls the
> multiplexer producer defined under a parent node.
> The driver corresponding to parent node provides register read/write
> capabilities.

This driver is just a rename of drivers/mux/mmio.c with a one-liner on
top. And there's a license change too. That's obnoxious. Please keep
this as GPL v2. Not that I /think/ Philipp nor Pengutronix cares deeply,
but what do I know? Changing the license as you copy the code is simply
not all right.

Anyway, I would prefer if you could extend drivers/mux/mmio.c to support
both compatibles, and using the compatible to select if

	regmap = syscon_node_to_regmap(np->parent);

or

	regmap = dev_get_regmap(dev->parent, NULL);
	
is called to get to the desired regmap.

Philipp, you don't object to extending the mmio driver, right?

Or are there more differences that I failed to notice?

Cheers,
Peter

> 
> Signed-off-by: Pankaj Bansal <pankaj.bansal@....com>
> ---
> 
> Notes:
>     Dependencies:
>     - https://patchwork.ozlabs.org/patch/1043790/
> 
>  drivers/mux/Kconfig  |  13 ++++
>  drivers/mux/Makefile |   2 +
>  drivers/mux/regmap.c | 139 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 154 insertions(+)
> 
> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> index 7659d6c5f718..a412d0955258 100644
> --- a/drivers/mux/Kconfig
> +++ b/drivers/mux/Kconfig
> @@ -58,4 +58,17 @@ config MUX_MMIO
>  	  To compile the driver as a module, choose M here: the module will
>  	  be called mux-mmio.
>  
> +config MUX_REGMAP
> +	tristate "Regmap register bitfield-controlled Multiplexer"
> +	depends on (OF && REGMAP) || COMPILE_TEST
> +	help
> +	  Regmap register bitfield-controlled Multiplexer controller.
> +
> +	  The driver builds multiplexer controllers for bitfields in a regmap
> +	  device 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 regmap-mmio.
> +
>  endmenu
> diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
> index 6e9fa47daf56..ae1bafac0cbd 100644
> --- a/drivers/mux/Makefile
> +++ b/drivers/mux/Makefile
> @@ -8,9 +8,11 @@ mux-adg792a-objs		:= adg792a.o
>  mux-adgs1408-objs		:= adgs1408.o
>  mux-gpio-objs			:= gpio.o
>  mux-mmio-objs			:= mmio.o
> +mux-regmap-objs			:= regmap.o
>  
>  obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
>  obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
>  obj-$(CONFIG_MUX_ADGS1408)	+= mux-adgs1408.o
>  obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
>  obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o
> +obj-$(CONFIG_MUX_REGMAP)	+= mux-regmap.o
> diff --git a/drivers/mux/regmap.c b/drivers/mux/regmap.c
> new file mode 100644
> index 000000000000..c2156302929a
> --- /dev/null
> +++ b/drivers/mux/regmap.c
> @@ -0,0 +1,139 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Regmap register bitfield-controlled multiplexer driver
> + *
> + * Based on drivers/mux/mmio.c
> + *
> + * Copyright 2019 NXP
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/mux/driver.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +static int mux_regmap_set(struct mux_control *mux, int state)
> +{
> +	struct regmap_field **fields = mux_chip_priv(mux->chip);
> +
> +	return regmap_field_write(fields[mux_control_get_index(mux)], state);
> +}
> +
> +static const struct mux_control_ops mux_regmap_ops = {
> +	.set = mux_regmap_set,
> +};
> +
> +static const struct of_device_id mux_regmap_dt_ids[] = {
> +	{ .compatible = "reg-mux", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mux_regmap_dt_ids);
> +
> +static int mux_regmap_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct regmap_field **fields;
> +	struct mux_chip *mux_chip;
> +	struct regmap *regmap;
> +	int num_fields;
> +	int ret;
> +	int i;
> +
> +	regmap = dev_get_regmap(dev->parent, NULL);
> +	if (IS_ERR(regmap)) {
> +		ret = PTR_ERR(regmap);
> +		dev_err(dev, "failed to get regmap: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = of_property_count_u32_elems(np, "mux-reg-masks");
> +	if (ret == 0 || ret % 2)
> +		ret = -EINVAL;
> +	if (ret < 0) {
> +		dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
> +			ret);
> +		return ret;
> +	}
> +	num_fields = ret / 2;
> +
> +	mux_chip = devm_mux_chip_alloc(dev, num_fields, num_fields *
> +				       sizeof(*fields));
> +	if (IS_ERR(mux_chip))
> +		return PTR_ERR(mux_chip);
> +
> +	fields = mux_chip_priv(mux_chip);
> +
> +	for (i = 0; i < num_fields; i++) {
> +		struct mux_control *mux = &mux_chip->mux[i];
> +		struct reg_field field;
> +		s32 idle_state = MUX_IDLE_AS_IS;
> +		u32 reg, mask;
> +		int bits;
> +
> +		ret = of_property_read_u32_index(np, "mux-reg-masks",
> +						 2 * i, &reg);
> +		if (!ret)
> +			ret = of_property_read_u32_index(np, "mux-reg-masks",
> +							 2 * i + 1, &mask);
> +		if (ret < 0) {
> +			dev_err(dev, "bitfield %d: failed to read mux-reg-masks property: %d\n",
> +				i, ret);
> +			return ret;
> +		}
> +
> +		field.reg = reg;
> +		field.msb = fls(mask) - 1;
> +		field.lsb = ffs(mask) - 1;
> +
> +		if (mask != GENMASK(field.msb, field.lsb)) {
> +			dev_err(dev, "bitfield %d: invalid mask 0x%x\n",
> +				i, mask);
> +			return -EINVAL;
> +		}
> +
> +		fields[i] = devm_regmap_field_alloc(dev, regmap, field);
> +		if (IS_ERR(fields[i])) {
> +			ret = PTR_ERR(fields[i]);
> +			dev_err(dev, "bitfield %d: failed allocate: %d\n",
> +				i, ret);
> +			return ret;
> +		}
> +
> +		bits = 1 + field.msb - field.lsb;
> +		mux->states = 1 << bits;
> +
> +		of_property_read_u32_index(np, "idle-states", i,
> +					   (u32 *)&idle_state);
> +		if (idle_state != MUX_IDLE_AS_IS) {
> +			if (idle_state < 0 || idle_state >= mux->states) {
> +				dev_err(dev, "bitfield: %d: out of range idle state %d\n",
> +					i, idle_state);
> +				return -EINVAL;
> +			}
> +
> +			mux->idle_state = idle_state;
> +		}
> +	}
> +
> +	mux_chip->ops = &mux_regmap_ops;
> +
> +	return devm_mux_chip_register(dev, mux_chip);
> +}
> +
> +static struct platform_driver mux_regmap_driver = {
> +	.driver = {
> +		.name = "regmap-mux",
> +		.of_match_table	= of_match_ptr(mux_regmap_dt_ids),
> +	},
> +	.probe = mux_regmap_probe,
> +};
> +module_platform_driver(mux_regmap_driver);
> +
> +MODULE_DESCRIPTION("Regmap register bitfield-controlled multiplexer driver");
> +MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@....com>");
> +MODULE_LICENSE("GPL");
> 

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