linux/drivers/net/phy/dp83tg720.c

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// SPDX-License-Identifier: GPL-2.0
/* Driver for the Texas Instruments DP83TG720 PHY
* Copyright (c) 2023 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
*/
#include <linux/bitfield.h>
#include <linux/ethtool_netlink.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/phy.h>
#include <linux/random.h>
#include "open_alliance_helpers.h"
/*
* DP83TG720 PHY Limitations and Workarounds
*
* The DP83TG720 1000BASE-T1 PHY has several limitations that require
* software-side mitigations. These workarounds are implemented throughout
* this driver. This section documents the known issues and their corresponding
* mitigation strategies.
*
* 1. Unreliable Link Detection and Synchronized Reset Deadlock
* ------------------------------------------------------------
* After a link loss or during link establishment, the DP83TG720 PHY may fail
* to detect or report link status correctly. As of June 2025, no public
* errata sheet for the DP83TG720 PHY documents this behavior.
* The "DP83TC81x, DP83TG72x Software Implementation Guide" application note
* (SNLA404, available at https://www.ti.com/lit/an/snla404/snla404.pdf)
* recommends performing a soft restart if polling for a link fails to establish
* a connection after 100ms. This procedure is adopted as the workaround for the
* observed link detection issue.
*
* However, in point-to-point setups where both link partners use the same
* driver (e.g. Linux on both sides), a synchronized reset pattern may emerge.
* This leads to a deadlock, where both PHYs reset at the same time and
* continuously miss each other during auto-negotiation.
*
* To address this, the reset procedure includes two components:
*
* - A **fixed minimum delay of 1ms** after a hardware reset. The datasheet
* "DP83TG720S-Q1 1000BASE-T1 Automotive Ethernet PHY with SGMII and RGMII"
* specifies this as the "Post reset stabilization-time prior to MDC preamble
* for register access" (T6.2), ensuring the PHY is ready for MDIO
* operations.
*
* - An **additional asymmetric delay**, empirically chosen based on
* master/slave role. This reduces the risk of synchronized resets on both
* link partners. Values are selected to avoid periodic overlap and ensure
* the link is re-established within a few cycles.
*
* The functions that implement this logic are:
* - dp83tg720_soft_reset()
* - dp83tg720_get_next_update_time()
*
* 2. Polling-Based Link Detection and IRQ Support
* -----------------------------------------------
* Due to the PHY-specific limitation described in section 1, link-up events
* cannot be reliably detected via interrupts on the DP83TG720. Therefore,
* polling is required to detect transitions from link-down to link-up.
*
* While link-down events *can* be detected via IRQs on this PHY, this driver
* currently does **not** implement interrupt support. As a result, all link
* state changes must be detected using polling.
*
* Polling behavior:
* - When the link is up: slow polling (e.g. 1s).
* - When the link just went down: fast polling for a short time.
* - When the link stays down: fallback to slow polling.
*
* This design balances responsiveness and CPU usage. It sacrifices fast link-up
* times in cases where the link is expected to remain down for extended periods,
* assuming that such systems do not require immediate reactivity.
*/
/*
* DP83TG720S_POLL_ACTIVE_LINK - Polling interval in milliseconds when the link
* is active.
* DP83TG720S_POLL_NO_LINK - Polling interval in milliseconds when the
* link is down.
* DP83TG720S_FAST_POLL_DURATION_MS - Timeout in milliseconds for no-link
* polling after which polling interval is
* increased.
* DP83TG720S_POLL_SLOW - Slow polling interval when there is no
* link for a prolongued period.
* DP83TG720S_RESET_DELAY_MS_MASTER - Delay after a reset before attempting
* to establish a link again for master phy.
* DP83TG720S_RESET_DELAY_MS_SLAVE - Delay after a reset before attempting
* to establish a link again for slave phy.
*
* These values are not documented or officially recommended by the vendor but
* were determined through empirical testing. They achieve a good balance in
* minimizing the number of reset retries while ensuring reliable link recovery
* within a reasonable timeframe.
*/
#define DP83TG720S_POLL_ACTIVE_LINK 421
#define DP83TG720S_POLL_NO_LINK 149
#define DP83TG720S_FAST_POLL_DURATION_MS 6000
#define DP83TG720S_POLL_SLOW 1117
#define DP83TG720S_RESET_DELAY_MS_MASTER 97
#define DP83TG720S_RESET_DELAY_MS_SLAVE 149
#define DP83TG720S_PHY_ID 0x2000a284
/* MDIO_MMD_VEND2 registers */
#define DP83TG720S_MII_REG_10 0x10
#define DP83TG720S_STS_MII_INT BIT(7)
#define DP83TG720S_LINK_STATUS BIT(0)
/* TDR Configuration Register (0x1E) */
#define DP83TG720S_TDR_CFG 0x1e
/* 1b = TDR start, 0b = No TDR */
#define DP83TG720S_TDR_START BIT(15)
/* 1b = TDR auto on link down, 0b = Manual TDR start */
#define DP83TG720S_CFG_TDR_AUTO_RUN BIT(14)
/* 1b = TDR done, 0b = TDR in progress */
#define DP83TG720S_TDR_DONE BIT(1)
/* 1b = TDR fail, 0b = TDR success */
#define DP83TG720S_TDR_FAIL BIT(0)
#define DP83TG720S_PHY_RESET 0x1f
#define DP83TG720S_HW_RESET BIT(15)
#define DP83TG720S_LPS_CFG3 0x18c
/* Power modes are documented as bit fields but used as values */
/* Power Mode 0 is Normal mode */
#define DP83TG720S_LPS_CFG3_PWR_MODE_0 BIT(0)
/* Open Aliance 1000BaseT1 compatible HDD.TDR Fault Status Register */
#define DP83TG720S_TDR_FAULT_STATUS 0x30f
/* Register 0x0301: TDR Configuration 2 */
#define DP83TG720S_TDR_CFG2 0x301
/* Register 0x0303: TDR Configuration 3 */
#define DP83TG720S_TDR_CFG3 0x303
/* Register 0x0304: TDR Configuration 4 */
#define DP83TG720S_TDR_CFG4 0x304
/* Register 0x0405: Unknown Register */
#define DP83TG720S_UNKNOWN_0405 0x405
#define DP83TG720S_LINK_QUAL_3 0x547
#define DP83TG720S_LINK_LOSS_CNT_MASK GENMASK(15, 10)
/* Register 0x0576: TDR Master Link Down Control */
#define DP83TG720S_TDR_MASTER_LINK_DOWN 0x576
#define DP83TG720S_RGMII_DELAY_CTRL 0x602
/* In RGMII mode, Enable or disable the internal delay for RXD */
#define DP83TG720S_RGMII_RX_CLK_SEL BIT(1)
/* In RGMII mode, Enable or disable the internal delay for TXD */
#define DP83TG720S_RGMII_TX_CLK_SEL BIT(0)
/*
* DP83TG720S_PKT_STAT_x registers correspond to similarly named registers
* in the datasheet (PKT_STAT_1 through PKT_STAT_6). These registers store
* 32-bit or 16-bit counters for TX and RX statistics and must be read in
* sequence to ensure the counters are cleared correctly.
*
* - DP83TG720S_PKT_STAT_1: Contains TX packet count bits [15:0].
* - DP83TG720S_PKT_STAT_2: Contains TX packet count bits [31:16].
* - DP83TG720S_PKT_STAT_3: Contains TX error packet count.
* - DP83TG720S_PKT_STAT_4: Contains RX packet count bits [15:0].
* - DP83TG720S_PKT_STAT_5: Contains RX packet count bits [31:16].
* - DP83TG720S_PKT_STAT_6: Contains RX error packet count.
*
* Keeping the register names as defined in the datasheet helps maintain
* clarity and alignment with the documentation.
*/
#define DP83TG720S_PKT_STAT_1 0x639
#define DP83TG720S_PKT_STAT_2 0x63a
#define DP83TG720S_PKT_STAT_3 0x63b
#define DP83TG720S_PKT_STAT_4 0x63c
#define DP83TG720S_PKT_STAT_5 0x63d
#define DP83TG720S_PKT_STAT_6 0x63e
/* Register 0x083F: Unknown Register */
#define DP83TG720S_UNKNOWN_083F 0x83f
#define DP83TG720S_SQI_REG_1 0x871
#define DP83TG720S_SQI_OUT_WORST GENMASK(7, 5)
#define DP83TG720S_SQI_OUT GENMASK(3, 1)
#define DP83TG720_SQI_MAX 7
struct dp83tg720_stats {
u64 link_loss_cnt;
u64 tx_pkt_cnt;
u64 tx_err_pkt_cnt;
u64 rx_pkt_cnt;
u64 rx_err_pkt_cnt;
};
struct dp83tg720_priv {
struct dp83tg720_stats stats;
unsigned long last_link_down_jiffies;
};
/**
* dp83tg720_update_stats - Update the PHY statistics for the DP83TD510 PHY.
* @phydev: Pointer to the phy_device structure.
*
* The function reads the PHY statistics registers and updates the statistics
* structure.
*
* Returns: 0 on success or a negative error code on failure.
*/
static int dp83tg720_update_stats(struct phy_device *phydev)
{
struct dp83tg720_priv *priv = phydev->priv;
u32 count;
int ret;
/* Read the link loss count */
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_LINK_QUAL_3);
if (ret < 0)
return ret;
/* link_loss_cnt */
count = FIELD_GET(DP83TG720S_LINK_LOSS_CNT_MASK, ret);
priv->stats.link_loss_cnt += count;
/* The DP83TG720S_PKT_STAT registers are divided into two groups:
* - Group 1 (TX stats): DP83TG720S_PKT_STAT_1 to DP83TG720S_PKT_STAT_3
* - Group 2 (RX stats): DP83TG720S_PKT_STAT_4 to DP83TG720S_PKT_STAT_6
*
* Registers in each group are cleared only after reading them in a
* plain sequence (e.g., 1, 2, 3 for Group 1 or 4, 5, 6 for Group 2).
* Any deviation from the sequence, such as reading 1, 2, 1, 2, 3, will
* prevent the group from being cleared. Additionally, the counters
* for a group are frozen as soon as the first register in that group
* is accessed.
*/
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_1);
if (ret < 0)
return ret;
/* tx_pkt_cnt_15_0 */
count = ret;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_2);
if (ret < 0)
return ret;
/* tx_pkt_cnt_31_16 */
count |= ret << 16;
priv->stats.tx_pkt_cnt += count;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_3);
if (ret < 0)
return ret;
/* tx_err_pkt_cnt */
priv->stats.tx_err_pkt_cnt += ret;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_4);
if (ret < 0)
return ret;
/* rx_pkt_cnt_15_0 */
count = ret;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_5);
if (ret < 0)
return ret;
/* rx_pkt_cnt_31_16 */
count |= ret << 16;
priv->stats.rx_pkt_cnt += count;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_PKT_STAT_6);
if (ret < 0)
return ret;
/* rx_err_pkt_cnt */
priv->stats.rx_err_pkt_cnt += ret;
return 0;
}
static int dp83tg720_soft_reset(struct phy_device *phydev)
{
int ret;
ret = phy_write(phydev, DP83TG720S_PHY_RESET, DP83TG720S_HW_RESET);
if (ret)
return ret;
/* Include mandatory MDC-access delay (1ms) + extra asymmetric delay to
* avoid synchronized reset deadlock. See section 1 in the top-of-file
* comment block.
*/
if (phydev->master_slave_state == MASTER_SLAVE_STATE_SLAVE)
msleep(DP83TG720S_RESET_DELAY_MS_SLAVE);
else
msleep(DP83TG720S_RESET_DELAY_MS_MASTER);
return ret;
}
static void dp83tg720_get_link_stats(struct phy_device *phydev,
struct ethtool_link_ext_stats *link_stats)
{
struct dp83tg720_priv *priv = phydev->priv;
link_stats->link_down_events = priv->stats.link_loss_cnt;
}
static void dp83tg720_get_phy_stats(struct phy_device *phydev,
struct ethtool_eth_phy_stats *eth_stats,
struct ethtool_phy_stats *stats)
{
struct dp83tg720_priv *priv = phydev->priv;
stats->tx_packets = priv->stats.tx_pkt_cnt;
stats->tx_errors = priv->stats.tx_err_pkt_cnt;
stats->rx_packets = priv->stats.rx_pkt_cnt;
stats->rx_errors = priv->stats.rx_err_pkt_cnt;
}
/**
* dp83tg720_cable_test_start - Start the cable test for the DP83TG720 PHY.
* @phydev: Pointer to the phy_device structure.
*
* This sequence is based on the documented procedure for the DP83TG720 PHY.
*
* Returns: 0 on success, a negative error code on failure.
*/
static int dp83tg720_cable_test_start(struct phy_device *phydev)
{
int ret;
/* Initialize the PHY to run the TDR test as described in the
* "DP83TG720S-Q1: Configuring for Open Alliance Specification
* Compliance (Rev. B)" application note.
* Most of the registers are not documented. Some of register names
* are guessed by comparing the register offsets with the DP83TD510E.
*/
/* Force master link down */
ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2,
DP83TG720S_TDR_MASTER_LINK_DOWN, 0x0400);
if (ret)
return ret;
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG2,
0xa008);
if (ret)
return ret;
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG3,
0x0928);
if (ret)
return ret;
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG4,
0x0004);
if (ret)
return ret;
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_UNKNOWN_0405,
0x6400);
if (ret)
return ret;
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_UNKNOWN_083F,
0x3003);
if (ret)
return ret;
/* Start the TDR */
ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG,
DP83TG720S_TDR_START);
if (ret)
return ret;
return 0;
}
/**
* dp83tg720_cable_test_get_status - Get the status of the cable test for the
* DP83TG720 PHY.
* @phydev: Pointer to the phy_device structure.
* @finished: Pointer to a boolean that indicates whether the test is finished.
*
* The function sets the @finished flag to true if the test is complete.
*
* Returns: 0 on success or a negative error code on failure.
*/
static int dp83tg720_cable_test_get_status(struct phy_device *phydev,
bool *finished)
{
int ret, stat;
*finished = false;
/* Read the TDR status */
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG);
if (ret < 0)
return ret;
/* Check if the TDR test is done */
if (!(ret & DP83TG720S_TDR_DONE))
return 0;
/* Check for TDR test failure */
if (!(ret & DP83TG720S_TDR_FAIL)) {
int location;
/* Read fault status */
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2,
DP83TG720S_TDR_FAULT_STATUS);
if (ret < 0)
return ret;
/* Get fault type */
stat = oa_1000bt1_get_ethtool_cable_result_code(ret);
/* Determine fault location */
location = oa_1000bt1_get_tdr_distance(ret);
if (location > 0)
ethnl_cable_test_fault_length(phydev,
ETHTOOL_A_CABLE_PAIR_A,
location);
} else {
/* Active link partner or other issues */
stat = ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
}
*finished = true;
ethnl_cable_test_result(phydev, ETHTOOL_A_CABLE_PAIR_A, stat);
/* save the current stats before resetting the PHY */
ret = dp83tg720_update_stats(phydev);
if (ret)
return ret;
return phy_init_hw(phydev);
}
static int dp83tg720_config_aneg(struct phy_device *phydev)
{
int ret;
/* Autoneg is not supported and this PHY supports only one speed.
* We need to care only about master/slave configuration if it was
* changed by user.
*/
ret = genphy_c45_pma_baset1_setup_master_slave(phydev);
if (ret)
return ret;
/* Re-read role configuration to make changes visible even if
* the link is in administrative down state.
*/
return genphy_c45_pma_baset1_read_master_slave(phydev);
}
static int dp83tg720_read_status(struct phy_device *phydev)
{
u16 phy_sts;
int ret;
phydev->pause = 0;
phydev->asym_pause = 0;
/* Most of Clause 45 registers are not present, so we can't use
* genphy_c45_read_status() here.
*/
phy_sts = phy_read(phydev, DP83TG720S_MII_REG_10);
phydev->link = !!(phy_sts & DP83TG720S_LINK_STATUS);
if (!phydev->link) {
/* save the current stats before resetting the PHY */
ret = dp83tg720_update_stats(phydev);
if (ret)
return ret;
/* According to the "DP83TC81x, DP83TG72x Software
* Implementation Guide", the PHY needs to be reset after a
* link loss or if no link is created after at least 100ms.
*/
ret = phy_init_hw(phydev);
if (ret)
return ret;
/* After HW reset we need to restore master/slave configuration.
* genphy_c45_pma_baset1_read_master_slave() call will be done
* by the dp83tg720_config_aneg() function.
*/
ret = dp83tg720_config_aneg(phydev);
if (ret)
return ret;
phydev->speed = SPEED_UNKNOWN;
phydev->duplex = DUPLEX_UNKNOWN;
} else {
/* PMA/PMD control 1 register (Register 1.0) is present, but it
* doesn't contain the link speed information.
* So genphy_c45_read_pma() can't be used here.
*/
ret = genphy_c45_pma_baset1_read_master_slave(phydev);
if (ret)
return ret;
phydev->duplex = DUPLEX_FULL;
phydev->speed = SPEED_1000;
}
return 0;
}
static int dp83tg720_get_sqi(struct phy_device *phydev)
{
int ret;
if (!phydev->link)
return 0;
ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_SQI_REG_1);
if (ret < 0)
return ret;
return FIELD_GET(DP83TG720S_SQI_OUT, ret);
}
static int dp83tg720_get_sqi_max(struct phy_device *phydev)
{
return DP83TG720_SQI_MAX;
}
static int dp83tg720_config_rgmii_delay(struct phy_device *phydev)
{
u16 rgmii_delay_mask;
u16 rgmii_delay = 0;
switch (phydev->interface) {
case PHY_INTERFACE_MODE_RGMII:
rgmii_delay = 0;
break;
case PHY_INTERFACE_MODE_RGMII_ID:
rgmii_delay = DP83TG720S_RGMII_RX_CLK_SEL |
DP83TG720S_RGMII_TX_CLK_SEL;
break;
case PHY_INTERFACE_MODE_RGMII_RXID:
rgmii_delay = DP83TG720S_RGMII_RX_CLK_SEL;
break;
case PHY_INTERFACE_MODE_RGMII_TXID:
rgmii_delay = DP83TG720S_RGMII_TX_CLK_SEL;
break;
default:
return 0;
}
rgmii_delay_mask = DP83TG720S_RGMII_RX_CLK_SEL |
DP83TG720S_RGMII_TX_CLK_SEL;
return phy_modify_mmd(phydev, MDIO_MMD_VEND2,
DP83TG720S_RGMII_DELAY_CTRL, rgmii_delay_mask,
rgmii_delay);
}
static int dp83tg720_config_init(struct phy_device *phydev)
{
int ret;
/* Reset the PHY to recover from a link failure */
ret = dp83tg720_soft_reset(phydev);
if (ret)
return ret;
if (phy_interface_is_rgmii(phydev)) {
ret = dp83tg720_config_rgmii_delay(phydev);
if (ret)
return ret;
}
/* In case the PHY is bootstrapped in managed mode, we need to
* wake it.
*/
ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_LPS_CFG3,
DP83TG720S_LPS_CFG3_PWR_MODE_0);
if (ret)
return ret;
/* Make role configuration visible for ethtool on init and after
* rest.
*/
return genphy_c45_pma_baset1_read_master_slave(phydev);
}
static int dp83tg720_probe(struct phy_device *phydev)
{
struct device *dev = &phydev->mdio.dev;
struct dp83tg720_priv *priv;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
phydev->priv = priv;
return 0;
}
/**
* dp83tg720_get_next_update_time - Return next polling interval for PHY state
* @phydev: Pointer to the phy_device structure
*
* Implements adaptive polling interval logic depending on link state and
* downtime duration. See the "2. Polling-Based Link Detection and IRQ Support"
* section at the top of this file for details.
*
* Return: Time (in jiffies) until the next poll
*/
static unsigned int dp83tg720_get_next_update_time(struct phy_device *phydev)
{
struct dp83tg720_priv *priv = phydev->priv;
unsigned int next_time_jiffies;
if (phydev->link) {
priv->last_link_down_jiffies = 0;
/* When the link is up, use a slower interval (in jiffies) */
next_time_jiffies =
msecs_to_jiffies(DP83TG720S_POLL_ACTIVE_LINK);
} else {
unsigned long now = jiffies;
if (!priv->last_link_down_jiffies)
priv->last_link_down_jiffies = now;
if (time_before(now, priv->last_link_down_jiffies +
msecs_to_jiffies(DP83TG720S_FAST_POLL_DURATION_MS))) {
/* Link recently went down: fast polling */
next_time_jiffies =
msecs_to_jiffies(DP83TG720S_POLL_NO_LINK);
} else {
/* Link has been down for a while: slow polling */
next_time_jiffies =
msecs_to_jiffies(DP83TG720S_POLL_SLOW);
}
}
/* Ensure the polling time is at least one jiffy */
return max(next_time_jiffies, 1U);
}
static struct phy_driver dp83tg720_driver[] = {
{
PHY_ID_MATCH_MODEL(DP83TG720S_PHY_ID),
.name = "TI DP83TG720S",
.flags = PHY_POLL_CABLE_TEST,
.probe = dp83tg720_probe,
.soft_reset = dp83tg720_soft_reset,
.config_aneg = dp83tg720_config_aneg,
.read_status = dp83tg720_read_status,
.get_features = genphy_c45_pma_read_ext_abilities,
.config_init = dp83tg720_config_init,
.get_sqi = dp83tg720_get_sqi,
.get_sqi_max = dp83tg720_get_sqi_max,
.cable_test_start = dp83tg720_cable_test_start,
.cable_test_get_status = dp83tg720_cable_test_get_status,
.get_link_stats = dp83tg720_get_link_stats,
.get_phy_stats = dp83tg720_get_phy_stats,
.update_stats = dp83tg720_update_stats,
.get_next_update_time = dp83tg720_get_next_update_time,
.suspend = genphy_suspend,
.resume = genphy_resume,
} };
module_phy_driver(dp83tg720_driver);
static const struct mdio_device_id __maybe_unused dp83tg720_tbl[] = {
{ PHY_ID_MATCH_MODEL(DP83TG720S_PHY_ID) },
{ }
};
MODULE_DEVICE_TABLE(mdio, dp83tg720_tbl);
MODULE_DESCRIPTION("Texas Instruments DP83TG720S PHY driver");
MODULE_AUTHOR("Oleksij Rempel <kernel@pengutronix.de>");
MODULE_LICENSE("GPL");