From: Girish K S <ks.giri@xxxxxxxxxxx> Added support for the EEE(Energy Efficient Ethernet) in 10G ethernet driver. Signed-off-by: Girish K S <ks.giri@xxxxxxxxxxx> Neatening-by: Joe Perches <joe@xxxxxxxxxxx> Signed-off-by: Byungho An <bh74.an@xxxxxxxxxxx> --- drivers/net/ethernet/samsung/sxgbe/sxgbe_common.h | 53 +++++++ drivers/net/ethernet/samsung/sxgbe/sxgbe_core.c | 86 +++++++++- drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c | 47 ++++++ drivers/net/ethernet/samsung/sxgbe/sxgbe_main.c | 165 +++++++++++++++++++- .../net/ethernet/samsung/sxgbe/sxgbe_platform.c | 4 + drivers/net/ethernet/samsung/sxgbe/sxgbe_reg.h | 5 + 6 files changed, 358 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_common.h b/drivers/net/ethernet/samsung/sxgbe/sxgbe_common.h index 587b691..937969c 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_common.h +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_common.h @@ -115,6 +115,33 @@ struct sxgbe_mtl_ops; #define RX_PTP_SIGNAL 0x0A #define RX_PTP_RESV_MSG 0x0F +/* EEE-LPI mode flags*/ +#define TX_ENTRY_LPI_MODE 0x10 +#define TX_EXIT_LPI_MODE 0x20 +#define RX_ENTRY_LPI_MODE 0x40 +#define RX_EXIT_LPI_MODE 0x80 + +/* EEE-LPI Interrupt status flag */ +#define LPI_INT_STATUS BIT(5) + +/* EEE-LPI Default timer values */ +#define LPI_LINK_STATUS_TIMER 0x3E8 +#define LPI_MAC_WAIT_TIMER 0x00 + +/* EEE-LPI Control and status definitions */ +#define LPI_CTRL_STATUS_TXA BIT(19) +#define LPI_CTRL_STATUS_PLSDIS BIT(18) +#define LPI_CTRL_STATUS_PLS BIT(17) +#define LPI_CTRL_STATUS_LPIEN BIT(16) +#define LPI_CTRL_STATUS_TXRSTP BIT(11) +#define LPI_CTRL_STATUS_RXRSTP BIT(10) +#define LPI_CTRL_STATUS_RLPIST BIT(9) +#define LPI_CTRL_STATUS_TLPIST BIT(8) +#define LPI_CTRL_STATUS_RLPIEX BIT(3) +#define LPI_CTRL_STATUS_RLPIEN BIT(2) +#define LPI_CTRL_STATUS_TLPIEX BIT(1) +#define LPI_CTRL_STATUS_TLPIEN BIT(0) + enum dma_irq_status { tx_hard_error = BIT(0), tx_bump_tc = BIT(1), @@ -199,6 +226,13 @@ struct sxgbe_extra_stats { unsigned long rx_buffer_access_err; unsigned long rx_data_transfer_err; + /* EEE-LPI stats */ + unsigned long tx_lpi_entry_n; + unsigned long tx_lpi_exit_n; + unsigned long rx_lpi_entry_n; + unsigned long rx_lpi_exit_n; + unsigned long eee_wakeup_error_n; + /* RX specific */ /* L2 error */ unsigned long rx_code_gmii_err; @@ -296,6 +330,13 @@ struct sxgbe_core_ops { unsigned char feature_index); /* adjust SXGBE speed */ void (*set_speed)(void __iomem *ioaddr, unsigned char speed); + + /* EEE-LPI specific operations */ + void (*set_eee_mode)(void __iomem *ioaddr); + void (*reset_eee_mode)(void __iomem *ioaddr); + void (*set_eee_timer)(void __iomem *ioaddr, const int ls, + const int tw); + void (*set_eee_pls)(void __iomem *ioaddr, const int link); }; const struct sxgbe_core_ops *sxgbe_get_core_ops(void); @@ -351,6 +392,8 @@ struct sxgbe_hw_features { /* IEEE 1588-2008 */ unsigned int atime_stamp; + unsigned int eee; + unsigned int tx_csum_offload; unsigned int rx_csum_offload; unsigned int multi_macaddr; @@ -434,6 +477,13 @@ struct sxgbe_priv_data { /* tc control */ int tx_tc; int rx_tc; + /* EEE-LPI specific members */ + struct timer_list eee_ctrl_timer; + bool tx_path_in_lpi_mode; + int lpi_irq; + int eee_enabled; + int eee_active; + int tx_lpi_timer; }; /* Function prototypes */ @@ -456,4 +506,7 @@ int sxgbe_restore(struct net_device *ndev); const struct sxgbe_mtl_ops *sxgbe_get_mtl_ops(void); +void sxgbe_disable_eee_mode(struct sxgbe_priv_data * const priv); +bool sxgbe_eee_init(struct sxgbe_priv_data * const priv); + #endif /* __SXGBE_COMMON_H__ */ diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_core.c b/drivers/net/ethernet/samsung/sxgbe/sxgbe_core.c index 17eea58..bf93b16 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_core.c +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_core.c @@ -47,11 +47,38 @@ static void sxgbe_core_dump_regs(void __iomem *ioaddr) { } +static int sxgbe_get_lpi_status(void __iomem *ioaddr, const u32 irq_status) +{ + int status = 0; + int lpi_status; + + /* Reading this register shall clear all the LPI status bits */ + lpi_status = readl(ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); + + if (lpi_status & LPI_CTRL_STATUS_TLPIEN) + status |= TX_ENTRY_LPI_MODE; + if (lpi_status & LPI_CTRL_STATUS_TLPIEX) + status |= TX_EXIT_LPI_MODE; + if (lpi_status & LPI_CTRL_STATUS_RLPIEN) + status |= RX_ENTRY_LPI_MODE; + if (lpi_status & LPI_CTRL_STATUS_RLPIEX) + status |= RX_EXIT_LPI_MODE; + + return status; +} + /* Handle extra events on specific interrupts hw dependent */ static int sxgbe_core_host_irq_status(void __iomem *ioaddr, struct sxgbe_extra_stats *x) { - return 0; + int irq_status, status = 0; + + irq_status = readl(ioaddr + SXGBE_CORE_INT_STATUS_REG); + + if (unlikely(irq_status & LPI_INT_STATUS)) + status |= sxgbe_get_lpi_status(ioaddr, irq_status); + + return status; } /* Set power management mode (e.g. magic frame) */ @@ -137,6 +164,59 @@ static void sxgbe_core_set_speed(void __iomem *ioaddr, unsigned char speed) writel(tx_cfg, ioaddr + SXGBE_CORE_TX_CONFIG_REG); } +static void sxgbe_set_eee_mode(void __iomem *ioaddr) +{ + u32 ctrl; + + /* Enable the LPI mode for transmit path with Tx automate bit set. + * When Tx Automate bit is set, MAC internally handles the entry + * to LPI mode after all outstanding and pending packets are + * transmitted. + */ + ctrl = readl(ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); + ctrl |= LPI_CTRL_STATUS_LPIEN | LPI_CTRL_STATUS_TXA; + writel(ctrl, ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); +} + +static void sxgbe_reset_eee_mode(void __iomem *ioaddr) +{ + u32 ctrl; + + ctrl = readl(ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); + ctrl &= ~(LPI_CTRL_STATUS_LPIEN | LPI_CTRL_STATUS_TXA); + writel(ctrl, ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); +} + +static void sxgbe_set_eee_pls(void __iomem *ioaddr, const int link) +{ + u32 ctrl; + + ctrl = readl(ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); + + /* If the PHY link status is UP then set PLS */ + if (link) + ctrl |= LPI_CTRL_STATUS_PLS; + else + ctrl &= ~LPI_CTRL_STATUS_PLS; + + writel(ctrl, ioaddr + SXGBE_CORE_LPI_CTRL_STATUS); +} + +static void sxgbe_set_eee_timer(void __iomem *ioaddr, + const int ls, const int tw) +{ + int value = ((tw & 0xffff)) | ((ls & 0x7ff) << 16); + + /* Program the timers in the LPI timer control register: + * LS: minimum time (ms) for which the link + * status from PHY should be ok before transmitting + * the LPI pattern. + * TW: minimum time (us) for which the core waits + * after it has stopped transmitting the LPI pattern. + */ + writel(value, ioaddr + SXGBE_CORE_LPI_TIMER_CTRL); +} + const struct sxgbe_core_ops core_ops = { .core_init = sxgbe_core_init, .dump_regs = sxgbe_core_dump_regs, @@ -149,6 +229,10 @@ const struct sxgbe_core_ops core_ops = { .get_controller_version = sxgbe_get_controller_version, .get_hw_feature = sxgbe_get_hw_feature, .set_speed = sxgbe_core_set_speed, + .set_eee_mode = sxgbe_set_eee_mode, + .reset_eee_mode = sxgbe_reset_eee_mode, + .set_eee_timer = sxgbe_set_eee_timer, + .set_eee_pls = sxgbe_set_eee_pls, }; const struct sxgbe_core_ops *sxgbe_get_core_ops(void) diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c b/drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c index 1dce2b2..9083300 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c @@ -32,10 +32,57 @@ struct sxgbe_stats { } static const struct sxgbe_stats sxgbe_gstrings_stats[] = { + SXGBE_STAT(tx_lpi_entry_n), + SXGBE_STAT(tx_lpi_exit_n), + SXGBE_STAT(rx_lpi_entry_n), + SXGBE_STAT(rx_lpi_exit_n), + SXGBE_STAT(eee_wakeup_error_n), }; #define SXGBE_STATS_LEN ARRAY_SIZE(sxgbe_gstrings_stats) +static int sxgbe_ethtool_get_eee(struct net_device *dev, + struct ethtool_eee *edata) +{ + struct sxgbe_priv_data *priv = netdev_priv(dev); + + if (!priv->hw_cap.eee) + return -EOPNOTSUPP; + + edata->eee_enabled = priv->eee_enabled; + edata->eee_active = priv->eee_active; + edata->tx_lpi_timer = priv->tx_lpi_timer; + + return phy_ethtool_get_eee(priv->phydev, edata); +} + +static int sxgbe_ethtool_set_eee(struct net_device *dev, + struct ethtool_eee *edata) +{ + struct sxgbe_priv_data *priv = netdev_priv(dev); + + priv->eee_enabled = edata->eee_enabled; + + if (!priv->eee_enabled) { + sxgbe_disable_eee_mode(priv); + } else { + /* We are asking for enabling the EEE but it is safe + * to verify all by invoking the eee_init function. + * In case of failure it will return an error. + */ + priv->eee_enabled = sxgbe_eee_init(priv); + if (!priv->eee_enabled) + return -EOPNOTSUPP; + + /* Do not change tx_lpi_timer in case of failure */ + priv->tx_lpi_timer = edata->tx_lpi_timer; + } + + return phy_ethtool_set_eee(priv->phydev, edata); +} + static const struct ethtool_ops sxgbe_ethtool_ops = { + .get_eee = sxgbe_ethtool_get_eee, + .set_eee = sxgbe_ethtool_set_eee, }; void sxgbe_set_ethtool_ops(struct net_device *netdev) diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_main.c b/drivers/net/ethernet/samsung/sxgbe/sxgbe_main.c index a8ba1a5..5490cf4 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_main.c +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_main.c @@ -55,6 +55,9 @@ #define SXGBE_DEFAULT_LPI_TIMER 1000 static int debug = -1; +static int eee_timer = SXGBE_DEFAULT_LPI_TIMER; + +module_param(eee_timer, int, S_IRUGO | S_IWUSR); module_param(debug, int, S_IRUGO | S_IWUSR); static const u32 default_msg_level = (NETIF_MSG_DRV | NETIF_MSG_PROBE | @@ -67,6 +70,97 @@ static irqreturn_t sxgbe_rx_interrupt(int irq, void *dev_id); #define SXGBE_COAL_TIMER(x) (jiffies + usecs_to_jiffies(x)) +#define SXGBE_LPI_TIMER(x) (jiffies + msecs_to_jiffies(x)) + +/** + * sxgbe_verify_args - verify the driver parameters. + * Description: it verifies if some wrong parameter is passed to the driver. + * Note that wrong parameters are replaced with the default values. + */ +static void sxgbe_verify_args(void) +{ + if (unlikely(eee_timer < 0)) + eee_timer = SXGBE_DEFAULT_LPI_TIMER; +} + +static void sxgbe_enable_eee_mode(const struct sxgbe_priv_data *priv) +{ + /* Check and enter in LPI mode */ + if (!priv->tx_path_in_lpi_mode) + priv->hw->mac->set_eee_mode(priv->ioaddr); +} + +void sxgbe_disable_eee_mode(struct sxgbe_priv_data * const priv) +{ + /* Exit and disable EEE in case of we are are in LPI state. */ + priv->hw->mac->reset_eee_mode(priv->ioaddr); + del_timer_sync(&priv->eee_ctrl_timer); + priv->tx_path_in_lpi_mode = false; +} + +/** + * sxgbe_eee_ctrl_timer + * @arg : data hook + * Description: + * If there is no data transfer and if we are not in LPI state, + * then MAC Transmitter can be moved to LPI state. + */ +static void sxgbe_eee_ctrl_timer(unsigned long arg) +{ + struct sxgbe_priv_data *priv = (struct sxgbe_priv_data *)arg; + + sxgbe_enable_eee_mode(priv); + mod_timer(&priv->eee_ctrl_timer, SXGBE_LPI_TIMER(eee_timer)); +} + +/** + * sxgbe_eee_init + * @priv: private device pointer + * Description: + * If the EEE support has been enabled while configuring the driver, + * if the GMAC actually supports the EEE (from the HW cap reg) and the + * phy can also manage EEE, so enable the LPI state and start the timer + * to verify if the tx path can enter in LPI state. + */ +bool sxgbe_eee_init(struct sxgbe_priv_data * const priv) +{ + bool ret = false; + + /* MAC core supports the EEE feature. */ + if (priv->hw_cap.eee) { + /* Check if the PHY supports EEE */ + if (phy_init_eee(priv->phydev, 1)) + return false; + + priv->eee_active = 1; + init_timer(&priv->eee_ctrl_timer); + priv->eee_ctrl_timer.function = sxgbe_eee_ctrl_timer; + priv->eee_ctrl_timer.data = (unsigned long)priv; + priv->eee_ctrl_timer.expires = SXGBE_LPI_TIMER(eee_timer); + add_timer(&priv->eee_ctrl_timer); + + priv->hw->mac->set_eee_timer(priv->ioaddr, + SXGBE_DEFAULT_LPI_TIMER, + priv->tx_lpi_timer); + + pr_info("Energy-Efficient Ethernet initialized\n"); + + ret = true; + } + + return ret; +} + +static void sxgbe_eee_adjust(const struct sxgbe_priv_data *priv) +{ + /* When the EEE has been already initialised we have to + * modify the PLS bit in the LPI ctrl & status reg according + * to the PHY link status. For this reason. + */ + if (priv->eee_enabled) + priv->hw->mac->set_eee_pls(priv->ioaddr, priv->phydev->link); +} + /** * sxgbe_clk_csr_set - dynamically set the MDC clock * @priv: driver private structure @@ -156,6 +250,9 @@ static void sxgbe_adjust_link(struct net_device *dev) if (new_state & netif_msg_link(priv)) phy_print_status(phydev); + + /* Alter the MAC settings for EEE */ + sxgbe_eee_adjust(priv); } /** @@ -678,7 +775,7 @@ static void sxgbe_tx_queue_clean(struct sxgbe_tx_queue *tqueue) * @priv: driver private structure * Description: it reclaims resources after transmission completes. */ -static void sxgbe_tx_all_clean(struct sxgbe_priv_data *priv) +static void sxgbe_tx_all_clean(struct sxgbe_priv_data * const priv) { u8 queue_num; @@ -686,6 +783,11 @@ static void sxgbe_tx_all_clean(struct sxgbe_priv_data *priv) struct sxgbe_tx_queue *tqueue = priv->txq[queue_num]; sxgbe_tx_queue_clean(tqueue); } + + if ((priv->eee_enabled) && (!priv->tx_path_in_lpi_mode)) { + sxgbe_enable_eee_mode(priv); + mod_timer(&priv->eee_ctrl_timer, SXGBE_LPI_TIMER(eee_timer)); + } } /** @@ -767,6 +869,7 @@ static int sxgbe_get_hw_features(struct sxgbe_priv_data * const priv) features->multi_macaddr = SXGBE_HW_FEAT_MACADDR_COUNT(rval); features->tstamp_srcselect = SXGBE_HW_FEAT_TSTMAP_SRC(rval); features->sa_vlan_insert = SXGBE_HW_FEAT_SRCADDR_VLAN(rval); + features->eee = SXGBE_HW_FEAT_EEE(rval); } /* Read First Capability Register CAP[1] */ rval = priv->hw->mac->get_hw_feature(priv->ioaddr, 1); @@ -986,6 +1089,20 @@ static int sxgbe_open(struct net_device *dev) goto init_error; } + /* If the LPI irq is different from the mac irq + * register a dedicated handler + */ + if (priv->lpi_irq != dev->irq) { + ret = devm_request_irq(priv->device, priv->lpi_irq, + sxgbe_common_interrupt, + IRQF_SHARED, dev->name, dev); + if (unlikely(ret < 0)) { + netdev_err(dev, "%s: ERROR: allocating the LPI IRQ %d (%d)\n", + __func__, priv->lpi_irq, ret); + goto init_error; + } + } + /* Request TX DMA irq lines */ SXGBE_FOR_EACH_QUEUE(SXGBE_TX_QUEUES, queue_num) { ret = devm_request_irq(priv->device, @@ -1041,6 +1158,9 @@ static int sxgbe_open(struct net_device *dev) priv->hw->dma->rx_watchdog(priv->ioaddr, SXGBE_MAX_DMA_RIWT); } + priv->tx_lpi_timer = SXGBE_DEFAULT_LPI_TIMER; + priv->eee_enabled = sxgbe_eee_init(priv); + napi_enable(&priv->napi); netif_start_queue(dev); @@ -1066,6 +1186,9 @@ static int sxgbe_release(struct net_device *dev) { struct sxgbe_priv_data *priv = netdev_priv(dev); + if (priv->eee_enabled) + del_timer_sync(&priv->eee_ctrl_timer); + /* Stop and disconnect the PHY */ if (priv->phydev) { phy_stop(priv->phydev); @@ -1159,6 +1282,9 @@ static netdev_tx_t sxgbe_xmit(struct sk_buff *skb, struct net_device *dev) /* get the spinlock */ spin_lock(&tqueue->tx_lock); + if (priv->tx_path_in_lpi_mode) + sxgbe_disable_eee_mode(priv); + if (unlikely(sxgbe_tx_avail(tqueue, tx_rsize) < nr_frags + 1)) { if (!netif_tx_queue_stopped(dev_txq)) { netif_tx_stop_queue(dev_txq); @@ -1433,6 +1559,25 @@ static void sxgbe_tx_timeout(struct net_device *dev) */ static irqreturn_t sxgbe_common_interrupt(int irq, void *dev_id) { + struct net_device *netdev = (struct net_device *)dev_id; + struct sxgbe_priv_data *priv = netdev_priv(netdev); + int status; + + status = priv->hw->mac->host_irq_status(priv->ioaddr, &priv->xstats); + /* For LPI we need to save the tx status */ + if (status & TX_ENTRY_LPI_MODE) { + priv->xstats.tx_lpi_entry_n++; + priv->tx_path_in_lpi_mode = true; + } + if (status & TX_EXIT_LPI_MODE) { + priv->xstats.tx_lpi_exit_n++; + priv->tx_path_in_lpi_mode = false; + } + if (status & RX_ENTRY_LPI_MODE) + priv->xstats.rx_lpi_entry_n++; + if (status & RX_EXIT_LPI_MODE) + priv->xstats.rx_lpi_exit_n++; + return IRQ_HANDLED; } @@ -1929,6 +2074,9 @@ struct sxgbe_priv_data *sxgbe_dvr_probe(struct device *device, priv->plat = plat_dat; priv->ioaddr = addr; + /* Verify driver arguments */ + sxgbe_verify_args(); + /* Init MAC and get the capabilities */ ret = sxgbe_hw_init(priv); if (ret) @@ -2102,7 +2250,21 @@ module_exit(sxgbe_exit); #ifndef MODULE static int __init sxgbe_cmdline_opt(char *str) { + char *opt; + + if (!str || !*str) + return -EINVAL; + while ((opt = strsep(&str, ",")) != NULL) { + if (!strncmp(opt, "eee_timer:", 6)) { + if (kstrtoint(opt + 10, 0, &eee_timer)) + goto err; + } + } return 0; + +err: + pr_err("%s: ERROR broken module parameter conversion\n", __func__); + return -EINVAL; } __setup("sxgbeeth=", sxgbe_cmdline_opt); @@ -2113,6 +2275,7 @@ __setup("sxgbeeth=", sxgbe_cmdline_opt); MODULE_DESCRIPTION("SAMSUNG 10G/2.5G/1G Ethernet PLATFORM driver"); MODULE_PARM_DESC(debug, "Message Level (-1: default, 0: no output, 16: all)"); +MODULE_PARM_DESC(eee_timer, "EEE-LPI Default LS timer value"); MODULE_AUTHOR("Siva Reddy Kallam <siva.kallam@xxxxxxxxxxx>"); MODULE_AUTHOR("ByungHo An <bh74.an@xxxxxxxxxxx>"); diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_platform.c b/drivers/net/ethernet/samsung/sxgbe/sxgbe_platform.c index 7345d37..d2edb7a 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_platform.c +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_platform.c @@ -162,6 +162,10 @@ static int sxgbe_platform_probe(struct platform_device *pdev) } } + priv->lpi_irq = irq_of_parse_and_map(dev->of_node, loop++); + if (priv->lpi_irq == -ENXIO) + priv->lpi_irq = priv->dev->irq; + platform_set_drvdata(pdev, priv->dev); pr_debug("platform driver registration completed\n"); diff --git a/drivers/net/ethernet/samsung/sxgbe/sxgbe_reg.h b/drivers/net/ethernet/samsung/sxgbe/sxgbe_reg.h index d1cd9ac..85a7b31 100644 --- a/drivers/net/ethernet/samsung/sxgbe/sxgbe_reg.h +++ b/drivers/net/ethernet/samsung/sxgbe/sxgbe_reg.h @@ -25,6 +25,11 @@ #define SXGBE_CORE_HASH_TABLE_REG5 0x0024 #define SXGBE_CORE_HASH_TABLE_REG6 0x0028 #define SXGBE_CORE_HASH_TABLE_REG7 0x002C + +/* EEE-LPI Registers */ +#define SXGBE_CORE_LPI_CTRL_STATUS 0x00D0 +#define SXGBE_CORE_LPI_TIMER_CTRL 0x00D4 + /* VLAN Specific Registers */ #define SXGBE_CORE_VLAN_TAG_REG 0x0050 #define SXGBE_CORE_VLAN_HASHTAB_REG 0x0058 -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html