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Date:   Mon, 18 Feb 2019 21:07:15 +0000
From:   Leo Li <leoyang.li@....com>
To:     Peter Rosin <peda@...ntia.se>,
        Pankaj Bansal <pankaj.bansal@....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



> -----Original Message-----
> From: Peter Rosin <peda@...ntia.se>
> Sent: Monday, February 18, 2019 8:28 AM
> 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
> 
> On 2019-02-18 11:20, Pankaj Bansal wrote:
> > 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 ?
> 
> Just keep the driver name as is, there is no shortage of drivers supporting
> more than one thing...

You are right that a lot of drivers support multiple functions.  But the problem here is that the current name mmio is only a subset of what the updated driver will handle, which can create confusion.

Regards,
Leo
> 
> Cheers,
> Peter
> 
> >>
> >> 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%2Fp
> >>> at
> >>>
> >>
> chwork.ozlabs.org%2Fpatch%2F1043790%2F&amp;data=02%7C01%7Cpankaj.
> b
> >> ansa
> >>>
> >>
> l%40nxp.com%7C3b8a1e8520ce4345105108d695861210%7C686ea1d3bc2b4c6
> f
> >> 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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