Subject: Re: [net-next PATCH v12 09/13] mfd: an8855: Add support for Airoha AN8855 Switch MFD

From: Lee Jones <[email-masked]>
Date: Fri, 14 Mar 2025 11:35:51 +0000

On Sun, 09 Mar 2025, Christian Marangi wrote:

> Add support for Airoha AN8855 Switch MFD that provide support for a DSA

Drop all references to MFD.

It doesn't exist.  It is a figment of your (and my) imagination.

> switch and a NVMEM provider. Also provide support for a virtual MDIO
> passthrough as the PHYs address for the switch are shared with the switch
> address.
> 
> Signed-off-by: Christian Marangi <[email-masked]>
> ---
>  MAINTAINERS                 |   1 +
>  drivers/mfd/Kconfig         |  10 +
>  drivers/mfd/Makefile        |   1 +
>  drivers/mfd/airoha-an8855.c | 445 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 457 insertions(+)
>  create mode 100644 drivers/mfd/airoha-an8855.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b7075425c94e..5844addbda2b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -730,6 +730,7 @@ F:	Documentation/devicetree/bindings/net/airoha,an8855-mdio.yaml
>  F:	Documentation/devicetree/bindings/net/airoha,an8855-phy.yaml
>  F:	Documentation/devicetree/bindings/net/dsa/airoha,an8855-switch.yaml
>  F:	Documentation/devicetree/bindings/nvmem/airoha,an8855-efuse.yaml
> +F:	drivers/mfd/airoha-an8855.c
>  
>  AIROHA ETHERNET DRIVER
>  M:	Lorenzo Bianconi <[email-masked]>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 6b0682af6e32..1b5abe5e2694 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -53,6 +53,16 @@ config MFD_ALTERA_SYSMGR
>  	  using regmap_mmio accesses for ARM32 parts and SMC calls to
>  	  EL3 for ARM64 parts.
>  
> +config MFD_AIROHA_AN8855

Should this be EN?

> +	tristate "Airoha AN8855 Switch MFD"
> +	select MFD_CORE
> +	select MDIO_DEVICE
> +	depends on NETDEVICES && OF
> +	help
> +	  Support for the Airoha AN8855 Switch MFD. This is a SoC Switch

Nit: "an SoC".

What kind of switch?

> +	  that provides various peripherals. Currently it provides a

Which other peripherals?

> +	  DSA switch and a NVMEM provider.
> +
>  config MFD_ACT8945A
>  	tristate "Active-semi ACT8945A"
>  	select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 9220eaf7cf12..37677f65a981 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_MFD_88PM860X)	+= 88pm860x.o
>  obj-$(CONFIG_MFD_88PM800)	+= 88pm800.o 88pm80x.o
>  obj-$(CONFIG_MFD_88PM805)	+= 88pm805.o 88pm80x.o
>  obj-$(CONFIG_MFD_88PM886_PMIC)	+= 88pm886.o
> +obj-$(CONFIG_MFD_AIROHA_AN8855)	+= airoha-an8855.o
>  obj-$(CONFIG_MFD_ACT8945A)	+= act8945a.o
>  obj-$(CONFIG_MFD_SM501)		+= sm501.o
>  obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835-pm.o
> diff --git a/drivers/mfd/airoha-an8855.c b/drivers/mfd/airoha-an8855.c
> new file mode 100644
> index 000000000000..0a6440bd4118
> --- /dev/null
> +++ b/drivers/mfd/airoha-an8855.c
> @@ -0,0 +1,445 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * MFD driver for Airoha AN8855 Switch

No such thing as an MFD driver.

Core is sometimes used in place of a better name.

> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mdio.h>
> +#include <linux/mdio/mdio-regmap.h>
> +#include <linux/module.h>
> +#include <linux/phy.h>
> +#include <linux/regmap.h>
> +
> +/* Register for hw trap status */

Ironically, this is probably the most readable name, yet it is the only
one graced with a comment.  Also 'hw' is an abbreviation, so it should be
HW or H/W or better yet hardware.

> +#define AN8855_HWTRAP			0x1000009c
> +
> +#define AN8855_CREV			0x10005000

Chip?

> +#define   AN8855_ID			0x8855

What kid of ID?  Chip, revision, model, serial?

> +#define AN8855_RG_GPHY_AFE_PWD		0x1028c840

No idea!

> +/* MII Registers */
> +#define AN8855_PHY_SELECT_PAGE		0x1f
> +#define   AN8855_PHY_PAGE		GENMASK(2, 0)
> +#define   AN8855_PHY_PAGE_STANDARD	FIELD_PREP_CONST(AN8855_PHY_PAGE, 0x0)
> +#define   AN8855_PHY_PAGE_EXTENDED_1	FIELD_PREP_CONST(AN8855_PHY_PAGE, 0x1)
> +#define   AN8855_PHY_PAGE_EXTENDED_4	FIELD_PREP_CONST(AN8855_PHY_PAGE, 0x4)
> +
> +/* MII Registers Page 4 */
> +#define AN8855_PBUS_MODE		0x10
> +#define   AN8855_PBUS_MODE_ADDR_FIXED	0x0
> +#define AN8855_PBUS_MODE_ADDR_INCR	BIT(15)
> +#define AN8855_PBUS_WR_ADDR_HIGH	0x11
> +#define AN8855_PBUS_WR_ADDR_LOW		0x12
> +#define AN8855_PBUS_WR_DATA_HIGH	0x13
> +#define AN8855_PBUS_WR_DATA_LOW		0x14
> +#define AN8855_PBUS_RD_ADDR_HIGH	0x15
> +#define AN8855_PBUS_RD_ADDR_LOW		0x16
> +#define AN8855_PBUS_RD_DATA_HIGH	0x17
> +#define AN8855_PBUS_RD_DATA_LOW		0x18
> +
> +struct an8855_mfd_priv {

It's not an "mfd".

> +	struct mii_bus *bus;
> +
> +	unsigned int switch_addr;
> +	u16 current_page;
> +};
> +
> +static const struct mfd_cell an8855_mfd_devs[] = {

"_child_" or "_sub_" or drop it entirely.

> +	{
> +		.name = "an8855-efuse",
> +		.of_compatible = "airoha,an8855-efuse",
> +	}, {
> +		.name = "an8855-switch",
> +		.of_compatible = "airoha,an8855-switch",
> +	}, {
> +		.name = "an8855-mdio",
> +		.of_compatible = "airoha,an8855-mdio",
> +	}
> +};
> +
> +static int an8855_mii_set_page(struct an8855_mfd_priv *priv, u8 phy_id,
> +			       u8 page) __must_hold(&priv->bus->mdio_lock)
> +{
> +	struct mii_bus *bus = priv->bus;
> +	int ret;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PHY_SELECT_PAGE, page);

Calling functions with '__' is a red flag.

> +	if (ret < 0)
> +		dev_err_ratelimited(&bus->dev,
> +				    "failed to set an8855 mii page\n");

Use 100-chars if it avoids these kind of line breaks.

> +	/* Cache current page if next mii read/write is for switch */

MII here?

"this switch"?

I don't see any checks here - how do we know if it is for switch or not?

> +	priv->current_page = page;
> +	return ret < 0 ? ret : 0;

You already check for 'ret < 0' at the call sites, so this little dance
is superfluous.

> +}
> +
> +static int an8855_mii_read32(struct mii_bus *bus, u8 phy_id, u32 reg,
> +			     u32 *val) __must_hold(&bus->mdio_lock)
> +{
> +	int lo, hi, ret;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_MODE,
> +			      AN8855_PBUS_MODE_ADDR_FIXED);

100-chars.

> +	if (ret < 0)
> +		goto err;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_RD_ADDR_HIGH,
> +			      upper_16_bits(reg));
> +	if (ret < 0)
> +		goto err;

'\n'

> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_RD_ADDR_LOW,
> +			      lower_16_bits(reg));
> +	if (ret < 0)
> +		goto err;
> +
> +	hi = __mdiobus_read(bus, phy_id, AN8855_PBUS_RD_DATA_HIGH);
> +	if (hi < 0) {
> +		ret = hi;
> +		goto err;
> +	}

'\n'

> +	lo = __mdiobus_read(bus, phy_id, AN8855_PBUS_RD_DATA_LOW);
> +	if (lo < 0) {
> +		ret = lo;
> +		goto err;
> +	}
> +
> +	*val = ((u16)hi << 16) | ((u16)lo & 0xffff);
> +
> +	return 0;
> +err:
> +	dev_err_ratelimited(&bus->dev,
> +			    "failed to read an8855 register\n");

dev_err() will already print out the an8855 part.

> +	return ret;
> +}
> +
> +static int an8855_regmap_read(void *ctx, uint32_t reg, uint32_t *val)
> +{
> +	struct an8855_mfd_priv *priv = ctx;
> +	struct mii_bus *bus = priv->bus;
> +	u16 addr = priv->switch_addr;
> +	int ret;
> +
> +	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);

guard()?

> +	ret = an8855_mii_set_page(priv, addr, AN8855_PHY_PAGE_EXTENDED_4);
> +	if (ret < 0)
> +		goto exit;
> +
> +	ret = an8855_mii_read32(bus, addr, reg, val);
> +
> +exit:
> +	mutex_unlock(&bus->mdio_lock);
> +
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static int an8855_mii_write32(struct mii_bus *bus, u8 phy_id, u32 reg,
> +			      u32 val) __must_hold(&bus->mdio_lock)
> +{
> +	int ret;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_MODE,
> +			      AN8855_PBUS_MODE_ADDR_FIXED);
> +	if (ret < 0)
> +		goto err;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_WR_ADDR_HIGH,
> +			      upper_16_bits(reg));
> +	if (ret < 0)
> +		goto err;
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_WR_ADDR_LOW,
> +			      lower_16_bits(reg));
> +	if (ret < 0)
> +		goto err;
> +
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_WR_DATA_HIGH,
> +			      upper_16_bits(val));
> +	if (ret < 0)
> +		goto err;
> +	ret = __mdiobus_write(bus, phy_id, AN8855_PBUS_WR_DATA_LOW,
> +			      lower_16_bits(val));
> +	if (ret < 0)
> +		goto err;
> +
> +	return 0;
> +err:
> +	dev_err_ratelimited(&bus->dev,
> +			    "failed to write an8855 register\n");
> +	return ret;
> +}
> +
> +static int an8855_regmap_write(void *ctx, uint32_t reg, uint32_t val)
> +{
> +	struct an8855_mfd_priv *priv = ctx;
> +	struct mii_bus *bus = priv->bus;
> +	u16 addr = priv->switch_addr;
> +	int ret;
> +
> +	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
> +	ret = an8855_mii_set_page(priv, addr, AN8855_PHY_PAGE_EXTENDED_4);
> +	if (ret < 0)
> +		goto exit;
> +
> +	ret = an8855_mii_write32(bus, addr, reg, val);
> +
> +exit:
> +	mutex_unlock(&bus->mdio_lock);
> +
> +	return ret < 0 ? ret : 0;

Doesn't the caller already expect possible >0 results?

> +}
> +
> +static int an8855_regmap_update_bits(void *ctx, uint32_t reg, uint32_t mask,
> +				     uint32_t write_val)
> +{
> +	struct an8855_mfd_priv *priv = ctx;
> +	struct mii_bus *bus = priv->bus;
> +	u16 addr = priv->switch_addr;
> +	u32 val;
> +	int ret;
> +
> +	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
> +	ret = an8855_mii_set_page(priv, addr, AN8855_PHY_PAGE_EXTENDED_4);
> +	if (ret < 0)
> +		goto exit;
> +
> +	ret = an8855_mii_read32(bus, addr, reg, &val);
> +	if (ret < 0)
> +		goto exit;
> +
> +	val &= ~mask;
> +	val |= write_val;
> +	ret = an8855_mii_write32(bus, addr, reg, val);
> +
> +exit:
> +	mutex_unlock(&bus->mdio_lock);
> +
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static const struct regmap_range an8855_readable_ranges[] = {
> +	regmap_reg_range(0x10000000, 0x10000fff), /* SCU */
> +	regmap_reg_range(0x10001000, 0x10001fff), /* RBUS */
> +	regmap_reg_range(0x10002000, 0x10002fff), /* MCU */
> +	regmap_reg_range(0x10005000, 0x10005fff), /* SYS SCU */
> +	regmap_reg_range(0x10007000, 0x10007fff), /* I2C Slave */
> +	regmap_reg_range(0x10008000, 0x10008fff), /* I2C Master */
> +	regmap_reg_range(0x10009000, 0x10009fff), /* PDMA */
> +	regmap_reg_range(0x1000a100, 0x1000a2ff), /* General Purpose Timer */
> +	regmap_reg_range(0x1000a200, 0x1000a2ff), /* GPU timer */
> +	regmap_reg_range(0x1000a300, 0x1000a3ff), /* GPIO */
> +	regmap_reg_range(0x1000a400, 0x1000a5ff), /* EFUSE */
> +	regmap_reg_range(0x1000c000, 0x1000cfff), /* GDMP CSR */
> +	regmap_reg_range(0x10010000, 0x1001ffff), /* GDMP SRAM */
> +	regmap_reg_range(0x10200000, 0x10203fff), /* Switch - ARL Global */
> +	regmap_reg_range(0x10204000, 0x10207fff), /* Switch - BMU */
> +	regmap_reg_range(0x10208000, 0x1020bfff), /* Switch - ARL Port */
> +	regmap_reg_range(0x1020c000, 0x1020cfff), /* Switch - SCH */
> +	regmap_reg_range(0x10210000, 0x10213fff), /* Switch - MAC */
> +	regmap_reg_range(0x10214000, 0x10217fff), /* Switch - MIB */
> +	regmap_reg_range(0x10218000, 0x1021bfff), /* Switch - Port Control */
> +	regmap_reg_range(0x1021c000, 0x1021ffff), /* Switch - TOP */
> +	regmap_reg_range(0x10220000, 0x1022ffff), /* SerDes */
> +	regmap_reg_range(0x10286000, 0x10286fff), /* RG Batcher */
> +	regmap_reg_range(0x1028c000, 0x1028ffff), /* ETHER_SYS */
> +	regmap_reg_range(0x30000000, 0x37ffffff), /* I2C EEPROM */
> +	regmap_reg_range(0x38000000, 0x3fffffff), /* BOOT_ROM */
> +	regmap_reg_range(0xa0000000, 0xbfffffff), /* GPHY */
> +};
> +
> +static const struct regmap_access_table an8855_readable_table = {
> +	.yes_ranges = an8855_readable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(an8855_readable_ranges),
> +};
> +
> +static const struct regmap_config an8855_regmap_config = {
> +	.name = "switch",
> +	.reg_bits = 32,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +	.max_register = 0xbfffffff,
> +	.reg_read = an8855_regmap_read,
> +	.reg_write = an8855_regmap_write,
> +	.reg_update_bits = an8855_regmap_update_bits,
> +	.disable_locking = true,
> +	.rd_table = &an8855_readable_table,
> +};
> +
> +static int an855_regmap_phy_reset_page(struct an8855_mfd_priv *priv,
> +				       int phy) __must_hold(&priv->bus->mdio_lock)
> +{
> +	/* Check PHY page only for addr shared with switch */
> +	if (phy != priv->switch_addr)
> +		return 0;
> +
> +	/* Don't restore page if it's not set to switch page */
> +	if (priv->current_page != FIELD_GET(AN8855_PHY_PAGE,
> +					    AN8855_PHY_PAGE_EXTENDED_4))
> +		return 0;
> +
> +	/* Restore page to 0, PHY might change page right after but that
> +	 * will be ignored as it won't be a switch page.
> +	 */

Use proper multi-line comments please.

> +	return an8855_mii_set_page(priv, phy, AN8855_PHY_PAGE_STANDARD);
> +}
> +
> +static int an8855_regmap_phy_read(void *ctx, uint32_t reg, uint32_t *val)
> +{
> +	struct an8855_mfd_priv *priv = ctx;
> +	struct mii_bus *bus = priv->bus;
> +	u16 phy_id, addr;
> +	int ret;
> +
> +	phy_id = FIELD_GET(MDIO_REGMAP_PHY_ADDR, reg);
> +	addr = FIELD_GET(MDIO_REGMAP_PHY_REG, reg);
> +
> +	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
> +	ret = an855_regmap_phy_reset_page(priv, phy_id);
> +	if (ret)
> +		goto exit;
> +
> +	ret = __mdiobus_read(priv->bus, phy_id, addr);
> +
> +exit:
> +	mutex_unlock(&bus->mdio_lock);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = ret;
> +	return 0;
> +}
> +
> +static int an8855_regmap_phy_write(void *ctx, uint32_t reg, uint32_t val)
> +{
> +	struct an8855_mfd_priv *priv = ctx;
> +	struct mii_bus *bus = priv->bus;
> +	u16 phy_id, addr;
> +	int ret;
> +
> +	phy_id = FIELD_GET(MDIO_REGMAP_PHY_ADDR, reg);
> +	addr = FIELD_GET(MDIO_REGMAP_PHY_REG, reg);
> +
> +	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
> +	ret = an855_regmap_phy_reset_page(priv, phy_id);
> +	if (ret)
> +		goto exit;
> +
> +	ret = __mdiobus_write(priv->bus, phy_id, addr, val);
> +
> +exit:
> +	mutex_unlock(&bus->mdio_lock);
> +
> +	return ret;
> +}
> +
> +/* Regmap for MDIO Passtrough
> + * PHY Addr and PHY Reg are encoded in the regmap register.
> + */
> +static const struct regmap_config an8855_regmap_phy_config = {
> +	.name = "phy",
> +	.reg_bits = 20,
> +	.val_bits = 16,
> +	.reg_stride = 1,
> +	.max_register = MDIO_REGMAP_PHY_ADDR | MDIO_REGMAP_PHY_REG,
> +	.reg_read = an8855_regmap_phy_read,
> +	.reg_write = an8855_regmap_phy_write,
> +	.disable_locking = true,
> +};
> +
> +static int an8855_read_switch_id(struct device *dev, struct regmap *regmap)
> +{
> +	u32 id;
> +	int ret;
> +
> +	ret = regmap_read(regmap, AN8855_CREV, &id);
> +	if (ret)
> +		return ret;
> +
> +	if (id != AN8855_ID) {
> +		dev_err(dev, "Switch ID detected %x but expected %x\n",

"Detected Switch ID %x but %x was expected"

Or

"Expected Switch ID %x but %x was detected"

> +			id, AN8855_ID);
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int an8855_mfd_probe(struct mdio_device *mdiodev)
> +{
> +	struct regmap *regmap, *regmap_phy;
> +	struct device *dev = &mdiodev->dev;
> +	struct an8855_mfd_priv *priv;
> +	struct gpio_desc *reset_gpio;
> +	u32 val;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->bus = mdiodev->bus;
> +	priv->switch_addr = mdiodev->addr;
> +	/* no DMA for mdiobus, mute warning for DMA mask not set */

Nit: Please start sentences with uppercase chars.

> +	dev->dma_mask = &dev->coherent_dma_mask;
> +
> +	regmap = devm_regmap_init(dev, NULL, priv, &an8855_regmap_config);
> +	if (IS_ERR(regmap))
> +		return dev_err_probe(dev, PTR_ERR(regmap),
> +				     "regmap initialization failed\n");
> +
> +	regmap_phy = devm_regmap_init(dev, NULL, priv, &an8855_regmap_phy_config);
> +	if (IS_ERR(regmap_phy))
> +		return dev_err_probe(dev, PTR_ERR(regmap_phy),
> +				     "regmap phy initialization failed\n");
> +
> +	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(reset_gpio))
> +		return PTR_ERR(reset_gpio);
> +
> +	if (reset_gpio) {
> +		usleep_range(100000, 150000);
> +		gpiod_set_value_cansleep(reset_gpio, 0);
> +		usleep_range(100000, 150000);
> +		gpiod_set_value_cansleep(reset_gpio, 1);
> +
> +		/* Poll HWTRAP reg to wait for Switch to fully Init */
> +		ret = regmap_read_poll_timeout(regmap, AN8855_HWTRAP, val,
> +					       val, 20, 200000);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = an8855_read_switch_id(dev, regmap);
> +	if (ret)
> +		return ret;
> +
> +	/* Release global PHY power down */
> +	ret = regmap_write(regmap, AN8855_RG_GPHY_AFE_PWD, 0x0);
> +	if (ret)
> +		return ret;
> +
> +	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO, an8855_mfd_devs,
> +				    ARRAY_SIZE(an8855_mfd_devs), NULL, 0,
> +				    NULL);
> +}
> +
> +static const struct of_device_id an8855_mfd_of_match[] = {
> +	{ .compatible = "airoha,an8855" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, an8855_mfd_of_match);
> +
> +static struct mdio_driver an8855_mfd_driver = {
> +	.probe = an8855_mfd_probe,
> +	.mdiodrv.driver = {
> +		.name = "an8855",
> +		.of_match_table = an8855_mfd_of_match,
> +	},
> +};
> +mdio_module_driver(an8855_mfd_driver);
> +
> +MODULE_AUTHOR("Christian Marangi <[email-masked]>");
> +MODULE_DESCRIPTION("Driver for Airoha AN8855 MFD");
> +MODULE_LICENSE("GPL");
> -- 
> 2.48.1
> 

-- 
Lee Jones [李琼斯]