driver: net: ethernet: cpsw: implement interrupt pacing via ethtool

This patch implements support for interrupt pacing block of CPSW via ethtool
Inetrrupt pacing block is common of both the ethernet interface in
dual emac mode
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpsw.c

@@ -126,6 +126,13 @@ do {								\
 #define CPSW_FIFO_DUAL_MAC_MODE		(1 << 15)
 #define CPSW_FIFO_RATE_LIMIT_MODE	(2 << 15)
 
+#define CPSW_INTPACEEN		(0x3f << 16)
+#define CPSW_INTPRESCALE_MASK	(0x7FF << 0)
+#define CPSW_CMINTMAX_CNT	63
+#define CPSW_CMINTMIN_CNT	2
+#define CPSW_CMINTMAX_INTVL	(1000 / CPSW_CMINTMIN_CNT)
+#define CPSW_CMINTMIN_INTVL	((1000 / CPSW_CMINTMAX_CNT) + 1)
+
 #define cpsw_enable_irq(priv)	\
 	do {			\
 		u32 i;		\
@@ -164,6 +171,15 @@ struct cpsw_wr_regs {
 	u32	rx_en;
 	u32	tx_en;
 	u32	misc_en;
+	u32	mem_allign1[8];
+	u32	rx_thresh_stat;
+	u32	rx_stat;
+	u32	tx_stat;
+	u32	misc_stat;
+	u32	mem_allign2[8];
+	u32	rx_imax;
+	u32	tx_imax;
+
 };
 
 struct cpsw_ss_regs {
@@ -318,6 +334,8 @@ struct cpsw_priv {
 	struct cpsw_host_regs __iomem	*host_port_regs;
 	u32				msg_enable;
 	u32				version;
+	u32				coal_intvl;
+	u32				bus_freq_mhz;
 	struct net_device_stats		stats;
 	int				rx_packet_max;
 	int				host_port;
@@ -616,6 +634,77 @@ static void cpsw_adjust_link(struct net_device *ndev)
 	}
 }
 
+static int cpsw_get_coalesce(struct net_device *ndev,
+				struct ethtool_coalesce *coal)
+{
+	struct cpsw_priv *priv = netdev_priv(ndev);
+
+	coal->rx_coalesce_usecs = priv->coal_intvl;
+	return 0;
+}
+
+static int cpsw_set_coalesce(struct net_device *ndev,
+				struct ethtool_coalesce *coal)
+{
+	struct cpsw_priv *priv = netdev_priv(ndev);
+	u32 int_ctrl;
+	u32 num_interrupts = 0;
+	u32 prescale = 0;
+	u32 addnl_dvdr = 1;
+	u32 coal_intvl = 0;
+
+	if (!coal->rx_coalesce_usecs)
+		return -EINVAL;
+
+	coal_intvl = coal->rx_coalesce_usecs;
+
+	int_ctrl =  readl(&priv->wr_regs->int_control);
+	prescale = priv->bus_freq_mhz * 4;
+
+	if (coal_intvl < CPSW_CMINTMIN_INTVL)
+		coal_intvl = CPSW_CMINTMIN_INTVL;
+
+	if (coal_intvl > CPSW_CMINTMAX_INTVL) {
+		/* Interrupt pacer works with 4us Pulse, we can
+		 * throttle further by dilating the 4us pulse.
+		 */
+		addnl_dvdr = CPSW_INTPRESCALE_MASK / prescale;
+
+		if (addnl_dvdr > 1) {
+			prescale *= addnl_dvdr;
+			if (coal_intvl > (CPSW_CMINTMAX_INTVL * addnl_dvdr))
+				coal_intvl = (CPSW_CMINTMAX_INTVL
+						* addnl_dvdr);
+		} else {
+			addnl_dvdr = 1;
+			coal_intvl = CPSW_CMINTMAX_INTVL;
+		}
+	}
+
+	num_interrupts = (1000 * addnl_dvdr) / coal_intvl;
+	writel(num_interrupts, &priv->wr_regs->rx_imax);
+	writel(num_interrupts, &priv->wr_regs->tx_imax);
+
+	int_ctrl |= CPSW_INTPACEEN;
+	int_ctrl &= (~CPSW_INTPRESCALE_MASK);
+	int_ctrl |= (prescale & CPSW_INTPRESCALE_MASK);
+	writel(int_ctrl, &priv->wr_regs->int_control);
+
+	cpsw_notice(priv, timer, "Set coalesce to %d usecs.\n", coal_intvl);
+	if (priv->data.dual_emac) {
+		int i;
+
+		for (i = 0; i < priv->data.slaves; i++) {
+			priv = netdev_priv(priv->slaves[i].ndev);
+			priv->coal_intvl = coal_intvl;
+		}
+	} else {
+		priv->coal_intvl = coal_intvl;
+	}
+
+	return 0;
+}
+
 static inline int __show_stat(char *buf, int maxlen, const char *name, u32 val)
 {
 	static char *leader = "........................................";
@@ -838,6 +927,14 @@ static int cpsw_ndo_open(struct net_device *ndev)
 		cpsw_info(priv, ifup, "submitted %d rx descriptors\n", i);
 	}
 
+	/* Enable Interrupt pacing if configured */
+	if (priv->coal_intvl != 0) {
+		struct ethtool_coalesce coal;
+
+		coal.rx_coalesce_usecs = (priv->coal_intvl << 4);
+		cpsw_set_coalesce(ndev, &coal);
+	}
+
 	cpdma_ctlr_start(priv->dma);
 	cpsw_intr_enable(priv);
 	napi_enable(&priv->napi);
@@ -1279,6 +1376,8 @@ static const struct ethtool_ops cpsw_ethtool_ops = {
 	.get_ts_info	= cpsw_get_ts_info,
 	.get_settings	= cpsw_get_settings,
 	.set_settings	= cpsw_set_settings,
+	.get_coalesce	= cpsw_get_coalesce,
+	.set_coalesce	= cpsw_set_coalesce,
 };
 
 static void cpsw_slave_init(struct cpsw_slave *slave, struct cpsw_priv *priv,
@@ -1466,6 +1565,9 @@ static int cpsw_probe_dual_emac(struct platform_device *pdev,
 	priv_sl2->slaves = priv->slaves;
 	priv_sl2->clk = priv->clk;
 
+	priv_sl2->coal_intvl = 0;
+	priv_sl2->bus_freq_mhz = priv->bus_freq_mhz;
+
 	priv_sl2->cpsw_res = priv->cpsw_res;
 	priv_sl2->regs = priv->regs;
 	priv_sl2->host_port = priv->host_port;
@@ -1575,6 +1677,8 @@ static int cpsw_probe(struct platform_device *pdev)
 		ret = -ENODEV;
 		goto clean_slave_ret;
 	}
+	priv->coal_intvl = 0;
+	priv->bus_freq_mhz = clk_get_rate(priv->clk) / 1000000;
 
 	priv->cpsw_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!priv->cpsw_res) {