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Date:   Mon, 18 Feb 2019 10:20:44 +0000
From:   Pankaj Bansal <pankaj.bansal@....com>
To:     Peter Rosin <peda@...ntia.se>, 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 Peter,

> -----Original Message-----
> From: Peter Rosin [mailto:peda@...ntia.se]
> Sent: Monday, 18 February, 2019 03:17 PM
> To: Pankaj Bansal <pankaj.bansal@....com>; Leo Li <leoyang.li@....com>;
> 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.

My Apologies. I will fix it as I send V2.

> 
> 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.

This can be done. The name mmio.c however suggests that mux is controlled by a Memory mapped device.
IMO, if the generic regmap API is to be added to it, the name needs to changed. Any suggestions ?

> 
> Philipp, you don't object to extending the mmio driver, right?
> 
> Or are there more differences that I failed to notice?

Nope, it's the only difference.

> 
> Cheers,
> Peter
> 
> >
> > Signed-off-by: Pankaj Bansal <pankaj.bansal@....com>
> > ---
> >
> > Notes:
> >     Dependencies:
> >     -
> > https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpat
> >
> chwork.ozlabs.org%2Fpatch%2F1043790%2F&amp;data=02%7C01%7Cpankaj.b
> ansa
> >
> l%40nxp.com%7C3b8a1e8520ce4345105108d695861210%7C686ea1d3bc2b4c6f
> a92cd
> >
> 99c5c301635%7C0%7C0%7C636860800396857042&amp;sdata=5e%2BhyasYwf
> uc%2Fbr
> > 1u6WKlKybYipz5c4ndBeLZDflHqk%3D&amp;reserved=0
> >
> >  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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