From 0f62a794b41ad14a962c70445844d61a8097805e Mon Sep 17 00:00:00 2001
From: Alex Marginean <alexandru.marginean@nxp.com>
Date: Tue, 20 Aug 2019 12:34:22 +0300
Subject: [PATCH] enetc: WA for MDIO register access issue

Due to a hardware issue access to MDIO registers concurrent with other
ENETC register access may lead to the MDIO access being dropped or
corrupted.  The workaround introduces locking for all register access in
ENETC space.  To reduce performance impact, code except MDIO uses per-cpu
locks, MDIO code having to acquire all per-CPU locks to perform an access.
To further reduce the performance impact, datapath functions acquire the
per-cpu lock fewer times and use _hot accessors.  All the rest of the code
uses the _wa accessors which lock every time a register is accessed.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
---
 drivers/net/ethernet/freescale/enetc/enetc.c      |  85 ++++++++++++++----
 drivers/net/ethernet/freescale/enetc/enetc_hw.h   | 105 +++++++++++++++++++++-
 drivers/net/ethernet/freescale/enetc/enetc_mdio.c |   4 +-
 drivers/net/ethernet/freescale/enetc/enetc_pf.c   |   3 +
 4 files changed, 176 insertions(+), 21 deletions(-)

--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -20,8 +20,13 @@ netdev_tx_t enetc_xmit(struct sk_buff *s
 {
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
 	struct enetc_bdr *tx_ring;
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
 	int count;
 
+	lock = this_cpu_ptr(&enetc_gregs);
+
 	tx_ring = priv->tx_ring[skb->queue_mapping];
 
 	if (unlikely(skb_shinfo(skb)->nr_frags > ENETC_MAX_SKB_FRAGS))
@@ -34,7 +39,12 @@ netdev_tx_t enetc_xmit(struct sk_buff *s
 		return NETDEV_TX_BUSY;
 	}
 
+	spin_lock_irqsave(lock, flags);
+
 	count = enetc_map_tx_buffs(tx_ring, skb, priv->active_offloads);
+
+	spin_unlock_irqrestore(lock, flags);
+
 	if (unlikely(!count))
 		goto drop_packet_err;
 
@@ -228,7 +238,7 @@ static int enetc_map_tx_buffs(struct ene
 	tx_ring->next_to_use = i;
 
 	/* let H/W know BD ring has been updated */
-	enetc_wr_reg(tx_ring->tpir, i); /* includes wmb() */
+	enetc_wr_reg_hot(tx_ring->tpir, i); /* includes wmb() */
 
 	return count;
 
@@ -249,13 +259,21 @@ dma_err:
 static irqreturn_t enetc_msix(int irq, void *data)
 {
 	struct enetc_int_vector	*v = data;
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
 	int i;
 
+	lock = this_cpu_ptr(&enetc_gregs);
+	spin_lock_irqsave(lock, flags);
+
 	/* disable interrupts */
-	enetc_wr_reg(v->rbier, 0);
+	enetc_wr_reg_hot(v->rbier, 0);
 
 	for_each_set_bit(i, &v->tx_rings_map, ENETC_MAX_NUM_TXQS)
-		enetc_wr_reg(v->tbier_base + ENETC_BDR_OFF(i), 0);
+		enetc_wr_reg_hot(v->tbier_base + ENETC_BDR_OFF(i), 0);
+
+	spin_unlock_irqrestore(lock, flags);
 
 	napi_schedule_irqoff(&v->napi);
 
@@ -271,6 +289,9 @@ static int enetc_poll(struct napi_struct
 	struct enetc_int_vector
 		*v = container_of(napi, struct enetc_int_vector, napi);
 	bool complete = true;
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
 	int work_done;
 	int i;
 
@@ -287,19 +308,24 @@ static int enetc_poll(struct napi_struct
 
 	napi_complete_done(napi, work_done);
 
+	lock = this_cpu_ptr(&enetc_gregs);
+	spin_lock_irqsave(lock, flags);
+
 	/* enable interrupts */
-	enetc_wr_reg(v->rbier, ENETC_RBIER_RXTIE);
+	enetc_wr_reg_hot(v->rbier, ENETC_RBIER_RXTIE);
 
 	for_each_set_bit(i, &v->tx_rings_map, ENETC_MAX_NUM_TXQS)
-		enetc_wr_reg(v->tbier_base + ENETC_BDR_OFF(i),
-			     ENETC_TBIER_TXTIE);
+		enetc_wr_reg_hot(v->tbier_base + ENETC_BDR_OFF(i),
+				 ENETC_TBIER_TXTIE);
+
+	spin_unlock_irqrestore(lock, flags);
 
 	return work_done;
 }
 
 static int enetc_bd_ready_count(struct enetc_bdr *tx_ring, int ci)
 {
-	int pi = enetc_rd_reg(tx_ring->tcir) & ENETC_TBCIR_IDX_MASK;
+	int pi = enetc_rd_reg_hot(tx_ring->tcir) & ENETC_TBCIR_IDX_MASK;
 
 	return pi >= ci ? pi - ci : tx_ring->bd_count - ci + pi;
 }
@@ -337,9 +363,18 @@ static bool enetc_clean_tx_ring(struct e
 	bool do_tstamp;
 	u64 tstamp = 0;
 
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
+
+	lock = this_cpu_ptr(&enetc_gregs);
+
 	i = tx_ring->next_to_clean;
 	tx_swbd = &tx_ring->tx_swbd[i];
+
+	spin_lock_irqsave(lock, flags);
 	bds_to_clean = enetc_bd_ready_count(tx_ring, i);
+	spin_unlock_irqrestore(lock, flags);
 
 	do_tstamp = false;
 
@@ -382,16 +417,20 @@ static bool enetc_clean_tx_ring(struct e
 			tx_swbd = tx_ring->tx_swbd;
 		}
 
+		spin_lock_irqsave(lock, flags);
+
 		/* BD iteration loop end */
 		if (is_eof) {
 			tx_frm_cnt++;
 			/* re-arm interrupt source */
-			enetc_wr_reg(tx_ring->idr, BIT(tx_ring->index) |
-				     BIT(16 + tx_ring->index));
+			enetc_wr_reg_hot(tx_ring->idr, BIT(tx_ring->index) |
+					 BIT(16 + tx_ring->index));
 		}
 
 		if (unlikely(!bds_to_clean))
 			bds_to_clean = enetc_bd_ready_count(tx_ring, i);
+
+		spin_unlock_irqrestore(lock, flags);
 	}
 
 	tx_ring->next_to_clean = i;
@@ -470,13 +509,14 @@ static int enetc_refill_rx_ring(struct e
 		rx_ring->next_to_alloc = i; /* keep track from page reuse */
 		rx_ring->next_to_use = i;
 		/* update ENETC's consumer index */
-		enetc_wr_reg(rx_ring->rcir, i);
+		enetc_wr_reg_hot(rx_ring->rcir, i);
 	}
 
 	return j;
 }
 
 #ifdef CONFIG_FSL_ENETC_HW_TIMESTAMPING
+/* Must be called with &enetc_gregs spinlock held */
 static void enetc_get_rx_tstamp(struct net_device *ndev,
 				union enetc_rx_bd *rxbd,
 				struct sk_buff *skb)
@@ -488,8 +528,8 @@ static void enetc_get_rx_tstamp(struct n
 	u64 tstamp;
 
 	if (le16_to_cpu(rxbd->r.flags) & ENETC_RXBD_FLAG_TSTMP) {
-		lo = enetc_rd(hw, ENETC_SICTR0);
-		hi = enetc_rd(hw, ENETC_SICTR1);
+		lo = enetc_rd_reg_hot(hw->reg + ENETC_SICTR0);
+		hi = enetc_rd_reg_hot(hw->reg + ENETC_SICTR1);
 		tstamp_lo = le32_to_cpu(rxbd->r.tstamp);
 		if (lo <= tstamp_lo)
 			hi -= 1;
@@ -627,6 +667,12 @@ static int enetc_clean_rx_ring(struct en
 	int rx_frm_cnt = 0, rx_byte_cnt = 0;
 	int cleaned_cnt, i;
 
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
+
+	lock = this_cpu_ptr(&enetc_gregs);
+
 	cleaned_cnt = enetc_bd_unused(rx_ring);
 	/* next descriptor to process */
 	i = rx_ring->next_to_clean;
@@ -637,6 +683,8 @@ static int enetc_clean_rx_ring(struct en
 		u32 bd_status;
 		u16 size;
 
+		spin_lock_irqsave(lock, flags);
+
 		if (cleaned_cnt >= ENETC_RXBD_BUNDLE) {
 			int count = enetc_refill_rx_ring(rx_ring, cleaned_cnt);
 
@@ -645,15 +693,19 @@ static int enetc_clean_rx_ring(struct en
 
 		rxbd = ENETC_RXBD(*rx_ring, i);
 		bd_status = le32_to_cpu(rxbd->r.lstatus);
-		if (!bd_status)
+		if (!bd_status) {
+			spin_unlock_irqrestore(lock, flags);
 			break;
+		}
 
-		enetc_wr_reg(rx_ring->idr, BIT(rx_ring->index));
+		enetc_wr_reg_hot(rx_ring->idr, BIT(rx_ring->index));
 		dma_rmb(); /* for reading other rxbd fields */
 		size = le16_to_cpu(rxbd->r.buf_len);
 		skb = enetc_map_rx_buff_to_skb(rx_ring, i, size);
-		if (!skb)
+		if (!skb) {
+			spin_unlock_irqrestore(lock, flags);
 			break;
+		}
 
 		enetc_get_offloads(rx_ring, rxbd, skb);
 
@@ -667,6 +719,7 @@ static int enetc_clean_rx_ring(struct en
 
 		if (unlikely(bd_status &
 			     ENETC_RXBD_LSTATUS(ENETC_RXBD_ERR_MASK))) {
+			spin_unlock_irqrestore(lock, flags);
 			dev_kfree_skb(skb);
 			while (!(bd_status & ENETC_RXBD_LSTATUS_F)) {
 				dma_rmb();
@@ -710,6 +763,8 @@ static int enetc_clean_rx_ring(struct en
 
 		enetc_process_skb(rx_ring, skb);
 
+		spin_unlock_irqrestore(lock, flags);
+
 		napi_gro_receive(napi, skb);
 
 		rx_frm_cnt++;
--- a/drivers/net/ethernet/freescale/enetc/enetc_hw.h
+++ b/drivers/net/ethernet/freescale/enetc/enetc_hw.h
@@ -327,8 +327,15 @@ struct enetc_hw {
 };
 
 /* general register accessors */
-#define enetc_rd_reg(reg)	ioread32((reg))
-#define enetc_wr_reg(reg, val)	iowrite32((val), (reg))
+#define enetc_rd_reg(reg)	enetc_rd_reg_wa((reg))
+#define enetc_wr_reg(reg, val)	enetc_wr_reg_wa((reg), (val))
+
+/* accessors for data-path, due to MDIO issue on LS1028 these should be called
+ * only under enetc_gregs per-cpu lock
+ */
+#define enetc_rd_reg_hot(reg)	ioread32((reg))
+#define enetc_wr_reg_hot(reg, val)	iowrite32((val), (reg))
+
 #ifdef ioread64
 #define enetc_rd_reg64(reg)	ioread64((reg))
 #else
@@ -347,12 +354,102 @@ static inline u64 enetc_rd_reg64(void __
 }
 #endif
 
+extern DEFINE_PER_CPU(spinlock_t, enetc_gregs);
+
+static inline u32 enetc_rd_reg_wa(void *reg)
+{
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
+	u32 val;
+
+	lock = this_cpu_ptr(&enetc_gregs);
+	spin_lock_irqsave(lock, flags);
+	val = ioread32(reg);
+	spin_unlock_irqrestore(lock, flags);
+
+	return val;
+}
+
+static inline void enetc_wr_reg_wa(void *reg, u32 val)
+{
+	unsigned long flags;
+	/* pointer to per-cpu ENETC lock for register access issue WA */
+	spinlock_t *lock;
+
+	lock = this_cpu_ptr(&enetc_gregs);
+	spin_lock_irqsave(lock, flags);
+	iowrite32(val, reg);
+	spin_unlock_irqrestore(lock, flags);
+}
+
+/* NR_CPUS=256 in ARM64 defconfig and using it as array size triggers stack
+ * frame warnings for the functions below.  Use a custom define of 2 for now,
+ * LS1028 has just two cores.
+ */
+#define ENETC_NR_CPU_LOCKS	2
+
+static inline u32 enetc_rd_reg_wa_single(void *reg)
+{
+	u32 val;
+	int cpu;
+	/* per-cpu ENETC lock array for register access issue WA */
+	spinlock_t *lock[ENETC_NR_CPU_LOCKS];
+	unsigned long flags;
+
+	local_irq_save(flags);
+	preempt_disable();
+
+	for_each_online_cpu(cpu) {
+		lock[cpu] = per_cpu_ptr(&enetc_gregs, cpu);
+		spin_lock(lock[cpu]);
+	}
+
+	val = ioread32(reg);
+
+	for_each_online_cpu(cpu)
+		spin_unlock(lock[cpu]);
+	local_irq_restore(flags);
+
+	preempt_enable();
+
+	return val;
+}
+
+static inline void enetc_wr_reg_wa_single(void *reg, u32 val)
+{
+	int cpu;
+	/* per-cpu ENETC lock array for register access issue WA */
+	spinlock_t *lock[ENETC_NR_CPU_LOCKS];
+	unsigned long flags;
+
+	local_irq_save(flags);
+	preempt_disable();
+
+	for_each_online_cpu(cpu) {
+		lock[cpu] = per_cpu_ptr(&enetc_gregs, cpu);
+		spin_lock(lock[cpu]);
+	}
+
+	iowrite32(val, reg);
+
+	for_each_online_cpu(cpu)
+		spin_unlock(lock[cpu]);
+	local_irq_restore(flags);
+
+	preempt_enable();
+}
+
 #define enetc_rd(hw, off)		enetc_rd_reg((hw)->reg + (off))
 #define enetc_wr(hw, off, val)		enetc_wr_reg((hw)->reg + (off), val)
 #define enetc_rd64(hw, off)		enetc_rd_reg64((hw)->reg + (off))
 /* port register accessors - PF only */
-#define enetc_port_rd(hw, off)		enetc_rd_reg((hw)->port + (off))
-#define enetc_port_wr(hw, off, val)	enetc_wr_reg((hw)->port + (off), val)
+#define enetc_port_rd(hw, off)		enetc_rd_reg_wa((hw)->port + (off))
+#define enetc_port_wr(hw, off, val)	enetc_wr_reg_wa((hw)->port + (off), val)
+#define enetc_port_rd_single(hw, off)		enetc_rd_reg_wa_single(\
+							(hw)->port + (off))
+#define enetc_port_wr_single(hw, off, val)	enetc_wr_reg_wa_single(\
+							(hw)->port + (off), val)
 /* global register accessors - PF only */
 #define enetc_global_rd(hw, off)	enetc_rd_reg((hw)->global + (off))
 #define enetc_global_wr(hw, off, val)	enetc_wr_reg((hw)->global + (off), val)
--- a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
@@ -16,13 +16,13 @@
 
 static inline u32 _enetc_mdio_rd(struct enetc_mdio_priv *mdio_priv, int off)
 {
-	return enetc_port_rd(mdio_priv->hw, mdio_priv->mdio_base + off);
+	return enetc_port_rd_single(mdio_priv->hw, mdio_priv->mdio_base + off);
 }
 
 static inline void _enetc_mdio_wr(struct enetc_mdio_priv *mdio_priv, int off,
 				  u32 val)
 {
-	enetc_port_wr(mdio_priv->hw, mdio_priv->mdio_base + off, val);
+	enetc_port_wr_single(mdio_priv->hw, mdio_priv->mdio_base + off, val);
 }
 
 #define enetc_mdio_rd(mdio_priv, off) \
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
@@ -1076,6 +1076,9 @@ static void enetc_pf_remove(struct pci_d
 	enetc_pci_remove(pdev);
 }
 
+DEFINE_PER_CPU(spinlock_t, enetc_gregs);
+EXPORT_PER_CPU_SYMBOL(enetc_gregs);
+
 static const struct pci_device_id enetc_pf_id_table[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_FREESCALE, ENETC_DEV_ID_PF) },
 	{ 0, } /* End of table. */
