Subject: Re: [PATCH v1] net: phy: Add driver for Motorcomm yt8521 gigabit ethernet phy

From: "Russell King (Oracle)" <[email-masked]>
Date: Mon, 20 Jun 2022 09:52:59 +0100

On Mon, Jun 20, 2022 at 10:36:21AM +0800, Frank wrote:
>  Add a driver for the motorcomm yt8521 gigabit ethernet phy. We have verified
>  the driver on StarFive VisionFive development board, which is developed by
>  Shanghai StarFive Technology Co., Ltd.. On the board, yt8521 gigabit ethernet
>  phy works in utp mode, RGMII interface, supports 1000M/100M/10M speeds, and
>  wol(magic package).
>  
> Signed-off-by: Frank <[email-masked]>
> ---
>  MAINTAINERS                 |   1 +
>  drivers/net/phy/Kconfig     |   2 +-
>  drivers/net/phy/motorcomm.c | 819 +++++++++++++++++++++++++++++++++++-
>  3 files changed, 817 insertions(+), 5 deletions(-)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a6d3bd9..59813c5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13437,6 +13437,7 @@ F:	include/uapi/linux/meye.h
>  
>  MOTORCOMM PHY DRIVER
>  M:	Peter Geis <[email-masked]>
> +M:	Frank <[email-masked]>
>  L:	[email-masked]
>  S:	Maintained
>  F:	drivers/net/phy/motorcomm.c
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index 9fee639..9061c76 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -253,7 +253,7 @@ config MOTORCOMM_PHY
>  	tristate "Motorcomm PHYs"
>  	help
>  	  Enables support for Motorcomm network PHYs.
> -	  Currently supports the YT8511 gigabit PHY.
> +	  Currently supports the YT8511, YT8521 Gigabit Ethernet PHYs.
>  
>  config NATIONAL_PHY
>  	tristate "National Semiconductor PHYs"
> diff --git a/drivers/net/phy/motorcomm.c b/drivers/net/phy/motorcomm.c
> index 7e6ac2c..2db2ef3 100644
> --- a/drivers/net/phy/motorcomm.c
> +++ b/drivers/net/phy/motorcomm.c
> @@ -1,15 +1,112 @@
>  // SPDX-License-Identifier: GPL-2.0+
>  /*
> - * Driver for Motorcomm PHYs
> + * motorcomm.c: Motorcomm 8511/8521 PHY driver.
>   *
> - * Author: Peter Geis <[email-masked]>
> + * Author: Frank <[email-masked]>
>   */
>  
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/phy.h>
> +#include <linux/netdevice.h>
> +#include <linux/etherdevice.h>
> +
> +// clang-format off
> +#define YTPHY_KERNEL_DRIVER_VERSION		"1.0.47"
> +#define YT8521_DRIVER_ENAME			"YT8521 Gigabit Ethernet"
> +
>  
>  #define PHY_ID_YT8511		0x0000010a
> +#define PHY_ID_YT8521				0x0000011A
> +#define YT_PHY_ID_MASK				0x00000FFF
> +
> +/* Specific Function Control Register */
> +#define YTPHY_SPECIFIC_FUNCTION_CONTROL_REG	0x10
> +
> +/* 2b00 Manual MDI configuration
> + * 2b01 Manual MDIX configuration
> + * 2b10 Reserved
> + * 2b11 Enable automatic crossover for all modes  *default*
> + */
> +#define YTPHY_SFCR_MDI_CROSSOVER_MODE_MASK	(BIT(6) | BIT(5))
> +#define YTPHY_SFCR_CROSSOVER_EN			BIT(3)
> +#define YTPHY_SFCR_SQE_TEST_EN			BIT(2)
> +#define YTPHY_SFCR_POLARITY_REVERSAL_EN		BIT(1)
> +#define YTPHY_SFCR_JABBER_DIS			BIT(0)
> +
> +/* Specific Status Register */
> +#define YTPHY_SPECIFIC_STATUS_REG		0x11
> +#define YTPHY_SSR_SPEED_MODE_BIT		14
> +
> +/* 2b00 10 Mbps
> + * 2b01 100 Mbps
> + * 2b10 1000 Mbps
> + * 2b11 Reserved
> + */
> +#define YTPHY_SSR_SPEED_MODE_MASK		(BIT(15) | BIT(14))
> +#define YTPHY_SSR_SPEED_10M			0x0
> +#define YTPHY_SSR_SPEED_100M			0x1
> +#define YTPHY_SSR_SPEED_1000M			0x2
> +#define YTPHY_SSR_DUPLEX_BIT			13
> +#define YTPHY_SSR_DUPLEX			BIT(13)
> +#define YTPHY_SSR_PAGE_RECEIVED			BIT(12)
> +#define YTPHY_SSR_SPEED_DUPLEX_RESOLVED		BIT(11)
> +#define YTPHY_SSR_LINK				BIT(10)
> +#define YTPHY_SSR_MDIX_CROSSOVER		BIT(6)
> +#define YTPHY_SSR_DOWNGRADE			BIT(5)
> +#define YTPHY_SSR_TRANSMIT_PAUSE		BIT(3)
> +#define YTPHY_SSR_RECEIVE_PAUSE			BIT(2)
> +#define YTPHY_SSR_POLARITY			BIT(1)
> +#define YTPHY_SSR_JABBER			BIT(0)
> +
> +/* Interrupt enable Register */
> +#define YTPHY_INTERRUPT_ENABLE_REG		0x12
> +#define YTPHY_IER_AUTONEG_ERR			BIT(15)
> +#define YTPHY_IER_SPEED_CHANGED			BIT(14)
> +#define YTPHY_IER_DUPLEX_CHANGED		BIT(13)
> +#define YTPHY_IER_PAGE_RECEIVED			BIT(12)
> +#define YTPHY_IER_LINK_FAILED			BIT(11)
> +#define YTPHY_IER_LINK_SUCCESSED		BIT(10)
> +#define YTPHY_IER_WOL				BIT(6)
> +#define YTPHY_IER_WIRESPEED_DOWNGRADE		BIT(5)
> +#define YTPHY_IER_SERDES_LINK_FAILED		BIT(3)
> +#define YTPHY_IER_SERDES_LINK_SUCCESSED		BIT(2)
> +#define YTPHY_IER_POLARITY_CHANGED		BIT(1)
> +#define YTPHY_IER_JABBER_HAPPENED		BIT(0)
> +
> +/* Interrupt Status Register */
> +#define YTPHY_INTERRUPT_STATUS_REG		0x13
> +#define YTPHY_ISR_AUTONEG_ERR			BIT(15)
> +#define YTPHY_ISR_SPEED_CHANGED			BIT(14)
> +#define YTPHY_ISR_DUPLEX_CHANGED		BIT(13)
> +#define YTPHY_ISR_PAGE_RECEIVED			BIT(12)
> +#define YTPHY_ISR_LINK_FAILED			BIT(11)
> +#define YTPHY_ISR_LINK_SUCCESSED		BIT(10)
> +#define YTPHY_ISR_WOL				BIT(6)
> +#define YTPHY_ISR_WIRESPEED_DOWNGRADE		BIT(5)
> +#define YTPHY_ISR_SERDES_LINK_FAILED		BIT(3)
> +#define YTPHY_ISR_SERDES_LINK_SUCCESSED		BIT(2)
> +#define YTPHY_ISR_POLARITY_CHANGED		BIT(1)
> +#define YTPHY_ISR_JABBER_HAPPENED		BIT(0)
> +
> +/* Speed Auto Downgrade Control Register */
> +#define YTPHY_SPEED_AUTO_DOWNGRADE_CONTROL_REG	0x14
> +#define YTPHY_SADCR_SPEED_DOWNGRADE_EN		BIT(5)
> +
> +/* If these bits are set to 3, the PHY attempts five times ( 3(set value) +
> + * additional 2) before downgrading, default 0x3
> + */
> +#define YTPHY_SADCR_SPEED_RETRY_LIMIT		(0x3 << 2)
> +
> +/* Rx Error Counter Register */
> +#define YTPHY_RX_ERROR_COUNTER_REG		0x15
> +
> +/* Extended Register's Address Offset Register */
> +#define YTPHY_PAGE_SELECT			0x1E
> +
> +/* Extended Register's Data Register */
> +#define YTPHY_PAGE_DATA				0x1F
> +
>  
>  #define YT8511_PAGE_SELECT	0x1e
>  #define YT8511_PAGE		0x1f
> @@ -38,6 +135,301 @@
>  #define YT8511_DELAY_FE_TX_EN	(0xf << 12)
>  #define YT8511_DELAY_FE_TX_DIS	(0x2 << 12)
>  
> +
> +/* Extended register is different from MMD Register and MII Register.
> + * We can use ytphy_read_ext/ytphy_write_ext/ytphy_modify_ext function to
> + * operate extended register.
> + * Extended Register  start
> + */
> +
> +#define YT8521_EXTREG_SLEEP_CONTROL1_REG	0x27
> +#define YT8521_ESC1R_SLEEP_SW			BIT(15)
> +#define YT8521_ESC1R_PLLON_SLP			BIT(14)
> +
> +#define YT8521_REG_SPACE_SELECT_REG		0xA000
> +#define YT8521_RSSR_FIBER_SPACE			BIT(1)
> +#define YT8521_RSSR_UTP_SPACE			0x0
> +
> +#define YT8521_CHIP_CONFIG_REG			0xA001
> +#define YT8521_CCR_SW_RST			BIT(15)
> +
> +/* 8 working modes:
> + * 3b000 UTP_TO_RGMII  *default*
> + * 3b001 FIBER_TO_RGMII
> + * 3b010 UTP_FIBER_TO_RGMII
> + * 3b011 UTP_TO_SGMII
> + * 3b100 SGPHY_TO_RGMAC
> + * 3b101 SGMAC_TO_RGPHY
> + * 3b110 UTP_TO_FIBER_AUTO
> + * 3b111 UTP_TO_FIBER_FORCE
> + */
> +#define YT8521_CCR_MODE_SEL_MASK		(BIT(2) | BIT(1) | BIT(0))
> +
> +/* 3 Phy register space pooling modes */
> +#define YT8521_MODE_FIBER			0x1
> +#define YT8521_MODE_UTP				0x2
> +#define YT8521_MODE_POLL			0x3
> +
> +#define YT8521_RGMII_CONFIG1_REG		0xA003
> +
> +/* TX Gig-E Delay is bits 3:0, default 0x1
> + * TX Fast-E Delay is bits 7:4, default 0xf
> + * RX Delay is bits 13:10, default 0x0
> + * Delay = 150ps * N
> + * On = 2250ps, off = 0ps
> + */
> +#define YT8521_RC1R_RX_DELAY_MASK		(0xF << 10)
> +#define YT8521_RC1R_RX_DELAY_EN			(0xF << 10)
> +#define YT8521_RC1R_RX_DELAY_DIS		(0x0 << 10)
> +#define YT8521_RC1R_FE_TX_DELAY_MASK		(0xF << 4)
> +#define YT8521_RC1R_FE_TX_DELAY_EN		(0xF << 4)
> +#define YT8521_RC1R_FE_TX_DELAY_DIS		(0x0 << 4)
> +#define YT8521_RC1R_GE_TX_DELAY_MASK		(0xF << 0)
> +#define YT8521_RC1R_GE_TX_DELAY_EN		(0xF << 0)
> +#define YT8521_RC1R_GE_TX_DELAY_DIS		(0x0 << 0)
> +
> +#define YTPHY_WOL_MACADDR2_REG			0xA007
> +#define YTPHY_WOL_MACADDR1_REG			0xA008
> +#define YTPHY_WOL_MACADDR0_REG			0xA009
> +
> +#define YTPHY_WOL_CONFIG_REG			0xA00A
> +#define YTPHY_WCR_INTR_SEL			BIT(6)
> +#define YTPHY_WCR_ENABLE			BIT(3)
> +
> +/* 2b00 84ms
> + * 2b01 168ms  *default*
> + * 2b10 336ms
> + * 2b11 672ms
> + */
> +#define YTPHY_WCR_PUSEL_WIDTH_MASK		(BIT(2) | BIT(1))
> +#define YTPHY_WCR_PUSEL_WIDTH_672MS		(BIT(2) | BIT(1))
> +
> +/* 1b0 Interrupt and WOL events is level triggerd and active LOW  *default*
> + * 1b1 Interrupt and WOL events is pulse triggered and active LOW
> + */
> +#define YTPHY_WCR_TYPE_PULSE			BIT(0)
> +
> +#define YTPHY_SYNC_CLK_CONFIG_REG		0xA012
> +
> +/* 1b1 output 125m clock  *default*
> + * 1b0 output 25m clock
> + */
> +#define YTPHY_SCCR_Clk_125M			BIT(3)
> +/* Extended Register  end */
> +
> +// clang-format on
> +
> +/**
> + * ytphy_read_ext() - read a PHY's extended register
> + * @phydev: a pointer to a &struct phy_device
> + * @regnum: register number to read
> + *
> + * returns the value of regnum reg or negative error code
> + */
> +static int ytphy_read_ext(struct phy_device *phydev, u16 regnum)
> +{
> +	int ret;
> +
> +	ret = phy_write(phydev, YTPHY_PAGE_SELECT, regnum);
> +	if (ret < 0)
> +		return ret;
> +
> +	return phy_read(phydev, YTPHY_PAGE_DATA);
> +}
> +
> +/**
> + * ytphy_write_ext() - write a PHY's extended register
> + * @phydev: a pointer to a &struct phy_device
> + * @regnum: register number to write
> + * @val: value to write to @regnum
> + *
> + * returns 0 or negative error code
> + */
> +static int ytphy_write_ext(struct phy_device *phydev, u16 regnum, u16 val)
> +{
> +	int ret;
> +
> +	ret = phy_write(phydev, YTPHY_PAGE_SELECT, regnum);
> +	if (ret < 0)
> +		return ret;
> +
> +	return phy_write(phydev, YTPHY_PAGE_DATA, val);
> +}
> +
> +/**
> + * ytphy_modify_ext() - bits modify a PHY's extended register
> + * @phydev: a pointer to a &struct phy_device
> + * @regnum: register number to write
> + * @mask: bit mask of bits to clear
> + * @set: bit mask of bits to set
> + *
> + * NOTE: Convenience function which allows a PHY‘s extended register to be
> + * modified as new register value = (old register value & ~mask) | set
> + *
> + * returns 0 or negative error code
> + */
> +static int ytphy_modify_ext(struct phy_device *phydev, u16 regnum, u16 mask,
> +			    u16 set)
> +{
> +	u16 val;
> +	int ret;
> +
> +	ret = ytphy_read_ext(phydev, regnum);
> +	if (ret < 0)
> +		return ret;
> +
> +	val = ret & 0xffff;
> +	val &= ~mask;
> +	val |= set;
> +
> +	return ytphy_write_ext(phydev, regnum, val);
> +}

The above functions don't look safe from userspace interference with the
YTPHY_PAGE_SELECT register to me, because they are taking the lock
around each individual PHY access.

> +
> +/**
> + * ytphy_read_page() - read reg page
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns current reg space of yt8521 (YT8521_RSSR_FIBER_SPACE /
> + * YT8521_RSSR_UTP_SPACE) or negative errno code
> + */
> +static int ytphy_read_page(struct phy_device *phydev)
> +{
> +	int ret;
> +
> +	ret = ytphy_read_ext(phydev, YT8521_REG_SPACE_SELECT_REG);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (ret & YT8521_RSSR_FIBER_SPACE)
> +		return YT8521_RSSR_FIBER_SPACE;
> +
> +	return YT8521_RSSR_UTP_SPACE;
> +};
> +
> +/**
> + * ytphy_write_page() - write reg page
> + * @phydev: a pointer to a &struct phy_device
> + * @page: The reg page(YT8521_RSSR_FIBER_SPACE/YT8521_RSSR_UTP_SPACE) to write.
> + *
> + * returns 0 or negative errno code
> + */
> +static int ytphy_write_page(struct phy_device *phydev, int page)
> +{
> +	int mask = YT8521_RSSR_FIBER_SPACE;
> +	int set = YT8521_RSSR_UTP_SPACE;
> +
> +	if (page == YT8521_RSSR_FIBER_SPACE)
> +		set = YT8521_RSSR_FIBER_SPACE;
> +
> +	return ytphy_modify_ext(phydev, YT8521_REG_SPACE_SELECT_REG, mask, set);
> +};

You fill these in as the .read_page and .write_page methods, but you
never use any of the paged accessors in this driver - so there's no
point filling in these methods.

You do call these directly, but again, it's all in a way that is unsafe
from userspace interference.

> +
> +/**
> + * ytphy_get_wol() - report whether wake-on-lan is enabled
> + * @phydev: a pointer to a &struct phy_device
> + * @wol: a pointer to a &struct ethtool_wolinfo
> + *
> + */
> +static void ytphy_get_wol(struct phy_device *phydev,
> +			  struct ethtool_wolinfo *wol)
> +{
> +	int val = 0;
> +
> +	wol->supported = WAKE_MAGIC;
> +	wol->wolopts = 0;
> +
> +	val = ytphy_read_ext(phydev, YTPHY_WOL_CONFIG_REG);
> +	if (val < 0)
> +		return;
> +
> +	if (val & YTPHY_WCR_ENABLE)
> +		wol->wolopts |= WAKE_MAGIC;
> +}
> +
> +/**
> + * ytphy_set_wol() - turn wake-on-lan on or off
> + * @phydev: a pointer to a &struct phy_device
> + * @wol: a pointer to a &struct ethtool_wolinfo
> + *
> + * returns 0 or negative errno code
> + */
> +static int ytphy_set_wol(struct phy_device *phydev, struct ethtool_wolinfo *wol)
> +{
> +	int ret;
> +	u16 mask;
> +	u16 val;
> +	u8 i;
> +	int curr_reg_space;
> +	const u8 *mac_addr;
> +	struct net_device *p_attached_dev;
> +	static const u16 mac_addr_reg[] = {
> +		YTPHY_WOL_MACADDR2_REG,
> +		YTPHY_WOL_MACADDR1_REG,
> +		YTPHY_WOL_MACADDR0_REG,
> +	};

Networking code likes variable declarations to be formatted as reverse
christmas tree.

> +
> +	curr_reg_space = ytphy_read_page(phydev);
> +	if (curr_reg_space < 0)
> +		return curr_reg_space;
> +
> +	if (wol->wolopts & WAKE_MAGIC) {
> +		p_attached_dev = phydev->attached_dev;
> +		if (!p_attached_dev)
> +			return -ENODEV;
> +
> +		mac_addr = (const u8 *)p_attached_dev->dev_addr;
> +		if (!is_valid_ether_addr(mac_addr))
> +			return -EINVAL;
> +
> +		/* switch to UTP reg space */
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +		if (ret < 0)
> +			goto err_restore_page;
> +
> +		/* Store the device address for the magic packet */
> +		for (i = 0; i < 3; i++) {
> +			ret = ytphy_write_ext(phydev, mac_addr_reg[i],
> +					      ((mac_addr[i * 2] << 8)) |
> +						      (mac_addr[i * 2 + 1]));
> +			if (ret < 0)
> +				goto err_restore_page;
> +		}
> +
> +		/* Enable the WOL feature */
> +		val = 0;
> +		mask = YTPHY_WCR_PUSEL_WIDTH_MASK | YTPHY_WCR_INTR_SEL;
> +		val |= YTPHY_WCR_ENABLE | YTPHY_WCR_INTR_SEL;
> +		val |= YTPHY_WCR_TYPE_PULSE | YTPHY_WCR_PUSEL_WIDTH_672MS;
> +		ret = ytphy_modify_ext(phydev, YTPHY_WOL_CONFIG_REG, mask, val);
> +		if (ret < 0)
> +			goto err_restore_page;
> +
> +		/* Enable the WOL feature interrupt */
> +		ret = phy_set_bits(phydev, YTPHY_INTERRUPT_ENABLE_REG,
> +				   YTPHY_IER_WOL);
> +		if (ret < 0)
> +			goto err_restore_page;
> +
> +	} else {
> +		/* switch to UTP reg space */
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +		if (ret < 0)
> +			goto err_restore_page;
> +
> +		/* Disable the WOL feature */
> +		val = 0;
> +		mask = YTPHY_WCR_ENABLE | YTPHY_WCR_INTR_SEL;
> +		ret = ytphy_modify_ext(phydev, YTPHY_WOL_CONFIG_REG, mask, val);
> +		if (ret < 0)
> +			goto err_restore_page;
> +	}
> +
> +err_restore_page:
> +	/* Recover to previous register space page */
> +	return ytphy_write_page(phydev, curr_reg_space);
> +}
> +
> +// clang-format off
>  static int yt8511_read_page(struct phy_device *phydev)
>  {
>  	return __phy_read(phydev, YT8511_PAGE_SELECT);
> @@ -111,6 +503,406 @@ err_restore_page:
>  	return phy_restore_page(phydev, oldpage, ret);
>  }
>  
> +// clang-format on
> +
> +/**
> + * yt8521_get_mode() - get the mode of yt8521(pooling mode)
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns current mode of yt8521 (YT8521_MODE_FIBER / YT8521_MODE_UTP /
> + * YT8521_MODE_POLL) or negative errno code
> + */
> +static int yt8521_get_mode(struct phy_device *phydev)
> +{
> +	int val = 0;

No need to initialise.

> +
> +	val = ytphy_read_ext(phydev, YT8521_CHIP_CONFIG_REG);
> +	if (val < 0)
> +		return val;
> +
> +	switch (val & YT8521_CCR_MODE_SEL_MASK) {
> +	case 1:
> +	case 4:
> +	case 5:
> +		return YT8521_MODE_FIBER;
> +	case 2:
> +	case 6:
> +	case 7:
> +		return YT8521_MODE_POLL;
> +	case 3:
> +	case 0:
> +		return YT8521_MODE_UTP;
> +	default: /* do not support other modes */
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +/**
> + * yt8521_adjust_status() - adjust speed and duplex according to is_utp, then
> + * update speed and duplex to phydev
> + *
> + * @phydev: a pointer to a &struct phy_device
> + * @status: yt8521 status read from YTPHY_SPECIFIC_STATUS_REG
> + * @is_utp: false(yt8521 work in fiber mode) or true(yt8521 work in utp mode)
> + *
> + * NOTE: there is no 10M speed mode in fiber mode, so need adjust.
> + *
> + * returns 0
> + */
> +static int yt8521_adjust_status(struct phy_device *phydev, int status,
> +				bool is_utp)
> +{
> +	int speed_mode, duplex;
> +	int speed = SPEED_UNKNOWN;

You always set "speed" so no need to initialise.

> +
> +	if (is_utp)
> +		duplex = (status & YTPHY_SSR_DUPLEX) >> YTPHY_SSR_DUPLEX_BIT;
> +	else
> +		duplex = 1;
> +
> +	speed_mode = (status & YTPHY_SSR_SPEED_MODE_MASK) >>
> +		     YTPHY_SSR_SPEED_MODE_BIT;
> +	switch (speed_mode) {
> +	case YTPHY_SSR_SPEED_10M:
> +		if (is_utp)
> +			speed = SPEED_10;
> +		break;
> +	case YTPHY_SSR_SPEED_100M:
> +		speed = SPEED_100;
> +		break;
> +	case YTPHY_SSR_SPEED_1000M:
> +		speed = SPEED_1000;
> +		break;
> +	default:
> +		speed = SPEED_UNKNOWN;
> +		break;
> +	}
> +
> +	phydev->speed = speed;
> +	phydev->duplex = duplex;
> +	phydev->port = is_utp ? PORT_TP : PORT_FIBRE;
> +
> +	return 0;
> +}
> +/**
> + * yt8521_read_status() -  determines the negotiated speed and duplex
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns 0 or negative errno code
> + */
> +static int yt8521_read_status(struct phy_device *phydev)
> +{
> +	int ret;
> +	int val;
> +	int yt8521_fiber_latch_val;
> +	int yt8521_fiber_curr_val;
> +	int link;
> +	int link_utp = 0, link_fiber = 0;
> +	int yt8521_mode;

Reverse christmas tree please.

> +
> +	yt8521_mode = yt8521_get_mode(phydev);
> +	if (yt8521_mode < 0)
> +		return yt8521_mode;
> +
> +	/* YT8521 has two reg space (utp/fiber) and three work mode (utp/fiber/poll),
> +	 * each reg space has YTPHY_SPECIFIC_STATUS_REG. The mode must be set
> +	 * before we can read the state (YTPHY_SPECIFIC_STATUS_REG). Pool mode
> +	 * combines utp and faber mode ,so we need do both.
> +	 */
> +
> +	if ((yt8521_mode == YT8521_MODE_UTP) ||
> +	    (yt8521_mode == YT8521_MODE_POLL)) {
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = genphy_read_status(phydev);
> +		if (ret)
> +			return ret;
> +
> +		val = phy_read(phydev, YTPHY_SPECIFIC_STATUS_REG);
> +		if (val < 0)
> +			return val;
> +
> +		link = val & YTPHY_SSR_LINK;
> +		if (link) {
> +			link_utp = 1;
> +			ret = yt8521_adjust_status(phydev, val, true);
> +			if (ret < 0)
> +				return ret;
> +		} else {
> +			link_utp = 0;
> +		}
> +	}
> +
> +	if ((yt8521_mode == YT8521_MODE_FIBER) ||
> +	    (yt8521_mode == YT8521_MODE_POLL)) {
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_FIBER_SPACE);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = genphy_read_status(phydev);
> +		if (ret)
> +			return ret;

As this is fibre, you probably don't want to be using this - it will
read the link partner advertisement from the PHY and interpret it as
if it were a copper advertisement, which it won't be.

> +
> +		val = phy_read(phydev, YTPHY_SPECIFIC_STATUS_REG);
> +		if (val < 0)
> +			return val;
> +
> +		/* When PHY is in fiber mode, speed transferred
> +		 * from 1000Mbps to 100Mbps, there is not link down
> +		 * from 0x11, so we need check reg 1 to identify such case.
> +		 */

This comment doesn't seem to convey much meaning unless one knows what
"0x11" is referring to - is it a register? Is it
YTPHY_SPECIFIC_STATUS_REG ?

It is quite normal for these registers to only provide only the
"current" status, and it is required to look at the BMSR to see whether
the link dropped since the last time BMSR was looked at.

> +		yt8521_fiber_latch_val = phy_read(phydev, MII_BMSR);
> +		if (yt8521_fiber_latch_val < 0)
> +			return yt8521_fiber_latch_val;
> +
> +		yt8521_fiber_curr_val = phy_read(phydev, MII_BMSR);
> +		if (yt8521_fiber_curr_val < 0)
> +			return yt8521_fiber_curr_val;

In any case, hasn't genphy_read_status() already read the BMSR just
before this?

> +
> +		link = val & YTPHY_SSR_LINK;
> +		if (link && yt8521_fiber_latch_val != yt8521_fiber_curr_val) {
> +			link = 0;
> +
> +			netdev_info(
> +				phydev->attached_dev,
> +				"%s, phy addr: %d, fiber link down detect, latch = %04x, curr = %04x\n",
> +				__func__, phydev->mdio.addr,
> +				yt8521_fiber_latch_val, yt8521_fiber_curr_val);
> +		}
> +		if (link) {
> +			link_fiber = 1;
> +			ret = yt8521_adjust_status(phydev, val, false);
> +			if (ret < 0)
> +				return ret;
> +		} else {
> +			link_fiber = 0;
> +		}
> +	}
> +
> +	if (link_utp || link_fiber) {
> +		if (phydev->link == 0)
> +			phydev->link = 1;
> +	} else {
> +		phydev->link = 0;
> +	}
> +
> +	/* set utp reg space as default reg space */
> +	return ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +}
> +
> +/**
> + * yt8521_modify_BMCR - bits modify a PHY's BMCR register according to the
> + * current mode
> + * @phydev: the phy_device struct
> + * @mask: bit mask of bits to clear
> + * @set: bit mask of bits to set
> + *
> + * NOTE: Convenience function which allows a PHY‘s BMCR register to be
> + * modified as new register value = (old register value & ~mask) | set.
> + * YT8521 has two space (utp/fiber) and three mode (utp/fiber/poll), each space
> + * has MII_BMCR. pool mode combines utp and faber,so need do both.
> + *
> + * returns 0 or negative errno code
> + */
> +static int yt8521_modify_BMCR(struct phy_device *phydev, u16 mask, u16 set)
> +{
> +	int ret;
> +	int yt8521_mode;
> +
> +	yt8521_mode = yt8521_get_mode(phydev);
> +	if (yt8521_mode < 0)
> +		return yt8521_mode;
> +
> +	if ((yt8521_mode == YT8521_MODE_UTP) ||
> +	    (yt8521_mode == YT8521_MODE_POLL)) {
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = phy_modify(phydev, MII_BMCR, mask, set);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	if ((yt8521_mode == YT8521_MODE_FIBER) ||
> +	    (yt8521_mode == YT8521_MODE_POLL)) {
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_FIBER_SPACE);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = phy_modify(phydev, MII_BMCR, mask, set);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* set utp reg apace as default reg apace*/
> +		ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
> +/**
> + * yt8521_soft_reset() - called to issue a PHY software reset
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns 0 or negative errno code
> + */
> +int yt8521_soft_reset(struct phy_device *phydev)
> +{
> +	return yt8521_modify_BMCR(phydev, 0, BMCR_RESET);
> +}
> +
> +/**
> + * yt8521_suspend() - suspend the hardware
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns 0 or negative errno code
> + */
> +int yt8521_suspend(struct phy_device *phydev)
> +{
> +	int val;
> +	int wol_enabled;
> +
> +	val = ytphy_read_ext(phydev, YTPHY_WOL_CONFIG_REG);
> +	if (val < 0)
> +		return val;
> +
> +	wol_enabled = (val & YTPHY_WCR_ENABLE);
> +	if (wol_enabled)
> +		val = BMCR_ISOLATE;
> +	else
> +		val = BMCR_PDOWN;
> +
> +	return yt8521_modify_BMCR(phydev, 0, val);
> +}
> +
> +/**
> + * yt8521_resume() - resume the hardware
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns 0 or negative errno code
> + */
> +int yt8521_resume(struct phy_device *phydev)
> +{
> +	int ret;
> +	/* disable auto sleep */
> +	ret = ytphy_modify_ext(phydev, YT8521_EXTREG_SLEEP_CONTROL1_REG,
> +			       YT8521_ESC1R_SLEEP_SW, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	return yt8521_modify_BMCR(phydev, BMCR_ISOLATE | BMCR_PDOWN, 0);
> +}
> +
> +/**
> + * yt8521_config_init() - called to initialize the PHY
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * returns 0 or negative errno code
> + */
> +static int yt8521_config_init(struct phy_device *phydev)
> +{
> +	int ret;
> +	u16 val = 0;
> +	int hw_strap_mode;
> +
> +	/* Explicitly switch to UTP reg space, just to be sure */
> +	ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = phy_read(phydev, MII_PHYSID2);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
> +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID)
> +		val |= (YT8521_RC1R_RX_DELAY_EN);
> +
> +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
> +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)
> +		val |= (YT8521_RC1R_GE_TX_DELAY_EN |
> +			YT8521_RC1R_FE_TX_DELAY_EN);
> +
> +	ret = ytphy_modify_ext(phydev, YT8521_RGMII_CONFIG1_REG,
> +			       (YT8521_RC1R_RX_DELAY_MASK |
> +				YT8521_RC1R_FE_TX_DELAY_MASK |
> +				YT8521_RC1R_GE_TX_DELAY_MASK),
> +			       val);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* disable auto sleep */
> +	ret = ytphy_modify_ext(phydev, YT8521_EXTREG_SLEEP_CONTROL1_REG,
> +			       YT8521_ESC1R_SLEEP_SW, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* enable RXC clock when no wire plug */
> +	ret = ytphy_modify_ext(phydev, 0xc, BIT(12), 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	hw_strap_mode = ytphy_read_ext(phydev, YT8521_CHIP_CONFIG_REG);
> +	if (hw_strap_mode < 0)
> +		return hw_strap_mode;
> +
> +	netdev_info(
> +		phydev->attached_dev,
> +		"%s done, phy addr: %d, strap mode = %ld, polling mode = %d\n",
> +		__func__, phydev->mdio.addr,
> +		hw_strap_mode & YT8521_CCR_MODE_SEL_MASK,
> +		yt8521_get_mode(phydev));
> +
> +	return ret;
> +}
> +
> +/**
> + * yt8521_aneg_done() - determines the auto negotiation result
> + * @phydev: a pointer to a &struct phy_device
> + *
> + * NOTE: for fiber mode, when speed is 100M, there is no definition for
> + * autonegotiation, and this function handles this case and return
> + * 1 per linux kernel's polling.
> + *
> + * returns 0(no link)or 1( fiber or utp link) or negative errno code
> + */
> +int yt8521_aneg_done(struct phy_device *phydev)
> +{
> +	int link_fiber = 0, link_utp = 0;
> +	int ret;
> +
> +	/* Explicitly switch to FIBER reg space*/
> +	ret = ytphy_write_page(phydev, YT8521_RSSR_FIBER_SPACE);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ytphy_write_page(phydev, YTPHY_SPECIFIC_STATUS_REG);
> +	if (ret < 0)
> +		return ret;
> +
> +	link_fiber = !!(ret & YTPHY_SSR_LINK);
> +
> +	/* Explicitly switch to UTP reg space */
> +	ret = ytphy_write_page(phydev, YT8521_RSSR_UTP_SPACE);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!link_fiber) {
> +		ret = ytphy_write_page(phydev, YTPHY_SPECIFIC_STATUS_REG);
> +		if (ret < 0)
> +			return ret;
> +
> +		link_fiber = !!(ret & YTPHY_SSR_LINK);

This doesn't look correct to me - why are you writing the page register
and then testing for bits in the return value (which is just the status
of the write operation) ?

> +	}
> +
> +	return !!(link_fiber | link_utp);
> +}
> +
> +// clang-format off
>  static struct phy_driver motorcomm_phy_drvs[] = {
>  	{
>  		PHY_ID_MATCH_EXACT(PHY_ID_YT8511),
> @@ -121,16 +913,35 @@ static struct phy_driver motorcomm_phy_drvs[] = {
>  		.read_page	= yt8511_read_page,
>  		.write_page	= yt8511_write_page,
>  	},
> +	{
> +		.phy_id		= PHY_ID_YT8521,
> +		.name		= YT8521_DRIVER_ENAME,
> +		.phy_id_mask	= YT_PHY_ID_MASK,
> +		.read_page	= ytphy_read_page,
> +		.write_page	= ytphy_write_page,
> +		.get_wol	= ytphy_get_wol,
> +		.set_wol	= ytphy_set_wol,
> +		.config_aneg	= genphy_config_aneg,

Does genphy_config_aneg do the right thing if you've left the PHY set to
the fibre page - as you can do after a call to yt8521_modify_BMCR() ?

I'm sure there will be more review comments to come, but I think at
least the above comments need to be considered before further review is
done.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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