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Date:   Mon, 18 Feb 2019 14:27:40 +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

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...

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%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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