Re: [PATCH v8 8/9] mfd: smpro-mfd: Adds Ampere's Altra SMpro MFD driver

[Quan Nguyen <quan@os.amperecomputing.com>]

Dear Lee Jones,

Thank you for the comment as on the link: 
https://lore.kernel.org/lkml/202204230554.4528TqPu-lkp@intel.com/T/#m476dce286d806bb3713f689663fa631f5a1f0909

I'm not sure what happen (maybe due to my bad junk filter) but I could 
only see your email when checking the link mentioned above.

I will try to response on each of your comment inline.

Thank you very much for the comment.
- Quan

On 22/04/2022 09:46, Quan Nguyen wrote:
> Adds Multi-function devices driver for SMpro co-processor found on the
[Lee] Please drop the term MFD and describe the device instead.

[Quan] Will replace MFD with "core" as your suggestion.

> Mt.Jade hardware reference platform with Ampere's Altra processor family.
> 
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> ---
> Changes in v8:
>    + None
> 
> Changes in v7:
>    + Smpro-mfd now significant changes in compare with simple-mfd-i2c
>      driver, remove the copyright note about simple-mfd-i2c    [Quan]
>    + Install bus->read/write()  to handle multiple types of bus
>      access.                                                   [Quan]
>    + Update license to MODULE_LICENSE("GPL")                   [Quan]
>    + Add others minor refactor the code                        [Quan]
> 
> Changes in v6:
>    + Update license part to reflect that this driver is clone from
>    simple-mfd-i2c driver [Quan]
> 
> Changes in v5:
>    + Dropped the use of simple-mfd-i2c driver [Quan]
>    + Introduced drivers/mfd/smpro-mfd.c driver to instantiate
>    sub-devices. This is to avoid DT nodes without resource issue [Quan]
>    + Revised commit message [Quan]
> 
> Changes in v4:
>    + Add "depends on I2C" to fix build issue found by kernel test
>    robot [Guenter]
> 
> Changes in v3:
>    + None
> 
> Changes in v2:
>    + Used 'struct of_device_id's .data attribute [Lee Jones]
> 
>   drivers/mfd/Kconfig     |  12 ++++
>   drivers/mfd/Makefile    |   1 +
>   drivers/mfd/smpro-mfd.c | 134 ++++++++++++++++++++++++++++++++++++++++
[Lee] Please drop the 'mfd' part.  Does 'core' work instead?

[Quan] Will drop the MFD thoroughly in next version.

>   3 files changed, 147 insertions(+)
>   create mode 100644 drivers/mfd/smpro-mfd.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 3b59456f5545..383d0e6cfb91 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -77,6 +77,18 @@ config MFD_AS3711
>   	help
>   	  Support for the AS3711 PMIC from AMS
>   
> +config MFD_SMPRO
> +	tristate "Ampere Computing MFD SMpro core driver"
> +	depends on I2C
> +	select MFD_CORE
> +	select REGMAP_I2C
> +	help
> +	  Say yes here to enable SMpro driver support for Ampere's Altra
> +	  processor family.
> +
> +	  Ampere's Altra SMpro exposes an I2C regmap interface that can
> +	  be accessed by child devices.
> +
>   config MFD_AS3722
>   	tristate "ams AS3722 Power Management IC"
>   	select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 858cacf659d6..36f8981cc4fd 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -266,6 +266,7 @@ obj-$(CONFIG_MFD_QCOM_PM8008)	+= qcom-pm8008.o
>   
>   obj-$(CONFIG_SGI_MFD_IOC3)	+= ioc3.o
>   obj-$(CONFIG_MFD_SIMPLE_MFD_I2C)	+= simple-mfd-i2c.o
> +obj-$(CONFIG_MFD_SMPRO)		+= smpro-mfd.o
>   obj-$(CONFIG_MFD_INTEL_M10_BMC)   += intel-m10-bmc.o
>   
>   obj-$(CONFIG_MFD_ATC260X)	+= atc260x-core.o
> diff --git a/drivers/mfd/smpro-mfd.c b/drivers/mfd/smpro-mfd.c
> new file mode 100644
> index 000000000000..485c4f89ebd9
> --- /dev/null
> +++ b/drivers/mfd/smpro-mfd.c
> @@ -0,0 +1,134 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Ampere Altra Family SMPro MFD - I2C
> + *
> + * Copyright (c) 2022, Ampere Computing LLC
> + * Author: Quan Nguyen <quan@os.amperecomputing..com>
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/mfd/core.h>
> +#include <linux/regmap.h>
> +
[Lee] Alphabetical.

[Quan] Will sort the included files follow alphbetical order in next 
version.

> +/* Identification Registers */
> +#define MANUFACTURER_ID_REG     0x02
> +#define AMPERE_MANUFACTURER_ID  0xCD3A
> +
> +static int smpro_mfd_write(void *context, const void *data, size_t count)
> +{
> +	struct device *dev = context;
> +	struct i2c_client *i2c = to_i2c_client(dev);
> +	int ret;
> +
> +	ret = i2c_master_send(i2c, data, count);
> +	if (ret == count)
> +		return 0;
> +	else if (ret < 0)
> +		return ret;
> +	else
> +		return -EIO;
> +}
> +
> +static int smpro_mfd_read(void *context, const void *reg, size_t reg_size,
> +			  void *val, size_t val_size)
> +{
> +	struct device *dev = context;
> +	struct i2c_client *i2c = to_i2c_client(dev);
> +	struct i2c_msg xfer[2];
> +	unsigned char buf[2];
> +	int ret;
> +
> +	xfer[0].addr = i2c->addr;
> +	xfer[0].flags = 0;
> +
> +	buf[0] = *(u8 *)reg;
> +	buf[1] = val_size;
> +	xfer[0].len = 2;
> +	xfer[0].buf = buf;
> +
> +	xfer[1].addr = i2c->addr;
> +	xfer[1].flags = I2C_M_RD;
> +	xfer[1].len = val_size;
> +	xfer[1].buf = val;
> +
> +	ret = i2c_transfer(i2c->adapter, xfer, 2);
> +	if (ret == 2)
> +		return 0;
> +	else if (ret < 0)
> +		return ret;
> +	else
> +		return -EIO;
> +}
> +
[Lee] This looks all too familiar.

I wonder how generic these i2c call-backs actually are.

[Quan] yes, this is similar with regmap_i2c_read() but with reg_size is 
force to 2.
We can reuse regmap_i2c_read() but it needs to be exported from 
drivers/base/regmap/regmap-i2c.c

> +static const struct regmap_bus smpro_regmap_bus = {
> +	.read = smpro_mfd_read,
> +	.write = smpro_mfd_write,
> +	.val_format_endian_default = REGMAP_ENDIAN_BIG,
> +};
> +
> +static bool smpro_mfd_readable_noinc_reg(struct device *dev, unsigned int reg)
> +{
> +	return  (reg == 0x82 || reg == 0x85 || reg == 0x92 || reg == 0x95 ||
> +		 reg == 0xC2 || reg == 0xC5 || reg == 0xD2 || reg == 0xDA);
> +}
[Lee] No magic numbers.  Please define these registers.

[Quan] Will fix this in next version.

> +
> +static const struct regmap_config smpro_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.readable_noinc_reg = smpro_mfd_readable_noinc_reg,
> +};
> +
> +static const struct mfd_cell smpro_devs[] = {
> +	MFD_CELL_NAME("smpro-hwmon"),
> +	MFD_CELL_NAME("smpro-errmon"),
> +	MFD_CELL_NAME("smpro-misc"),
> +};
> +
> +static int smpro_mfd_probe(struct i2c_client *i2c)
> +{
> +	const struct regmap_config *config;
> +	struct regmap *regmap;
> +	unsigned int val;
> +	int ret;
> +
> +	config = device_get_match_data(&i2c->dev);
> +	if (!config)
> +		config = &smpro_regmap_config;
> +
[Lee] This use-case is not currently supported.

Please return an error instead.

[Quan] Will update in next version.

> +	regmap = devm_regmap_init(&i2c->dev, &smpro_regmap_bus, &i2c->dev, config);
> +	if (IS_ERR(regmap))
> +		return PTR_ERR(regmap);
> +
> +	/* Check for valid ID */
[Lee] Decent #define nomenclature should render this comment superfluous.

[Quan] Thanks, will remove in next version.

> +	ret = regmap_read(regmap, MANUFACTURER_ID_REG, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != AMPERE_MANUFACTURER_ID)
> +		return -ENODEV;
> +
> +	return devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO,
> +				    smpro_devs, ARRAY_SIZE(smpro_devs), NULL, 0, NULL);
> +}
> +
> +static const struct of_device_id smpro_mfd_of_match[] = {
> +	{ .compatible = "ampere,smpro", .data = &smpro_regmap_config },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, smpro_mfd_of_match);
> +
> +static struct i2c_driver smpro_mfd_driver = {
> +	.probe_new = smpro_mfd_probe,
> +	.driver = {
> +		.name = "smpro-mfd-i2c",
[Lee] "smpro-core"

[Quan] Will change mfd to "core" thoroughly.
Thanks for the review.

> +		.of_match_table = smpro_mfd_of_match,
> +	},
> +};
> +module_i2c_driver(smpro_mfd_driver);
> +
> +MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
> +MODULE_DESCRIPTION("SMPRO MFD - I2C driver");
> +MODULE_LICENSE("GPL");