Re: [PATCH] drivers: mux: Generic register bitfield-based multiplexer driver

From: Peter Rosin
Date: Mon Feb 18 2019 - 09:27:51 EST

On 2019-02-18 11:20, Pankaj Bansal wrote:
> Hi Peter,
>
>> -----Original Message-----
>> From: Peter Rosin [mailto:peda@xxxxxxxxxx]
>> Sent: Monday, 18 February, 2019 03:17 PM
>> To: Pankaj Bansal <pankaj.bansal@xxxxxxx>; Leo Li <leoyang.li@xxxxxxx>;
>> linux-kernel@xxxxxxxxxxxxxxx; Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
>> 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@xxxxxxx>
>>> ---
>>>
>>> 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@xxxxxxx>");
>>> +MODULE_LICENSE("GPL");
>>>
>