commit 86c432ca5d6da90a26ac8d3e680f2268b502d9c5
author Ben Hutchings <bhutchings@solarflare.com> Thu Sep 01 12:09:29 2011 +0000
committer David S. Miller <davem@davemloft.net> Thu Sep 15 17:31:28 2011 -0400
tree 6db2e039f5cecfbc1643f46e2da5c18ae9aaabe5
parent 883cb075833e7e4356207569e0daefa2c2a3f700

Revert "sfc: Use write-combining to reduce TX latency" and follow-ups

This reverts commits 65f0b417dee94f779ce9b77102b7d73c93723b39,
d88d6b05fee3cc78e5b0273eb58c31201dcc6b76,
fcfa060468a4edcf776f0c1211d826d5de1668c1,
747df2258b1b9a2e25929ef496262c339c380009 and
867955f5682f7157fdafe8670804b9f8ea077bc7.

Depending on the processor model, write-combining may result in
reordering that the NIC will not tolerate.  This typically results
in a DMA error event and reset by the driver, logged as:

sfc 0000:0e:00.0: eth2: TX DMA Q reports TX_EV_PKT_ERR.
sfc 0000:0e:00.0: eth2: resetting (ALL)

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/mcdi.c

diff --git a/drivers/net/sfc/mcdi.c b/drivers/net/sfc/mcdi.c
index 3dd45ed..81a4253 100644
--- a/drivers/net/sfc/mcdi.c
+++ b/drivers/net/sfc/mcdi.c
@@ -50,20 +50,6 @@
 	return &nic_data->mcdi;
 }
 
-static inline void
-efx_mcdi_readd(struct efx_nic *efx, efx_dword_t *value, unsigned reg)
-{
-	struct siena_nic_data *nic_data = efx->nic_data;
-	value->u32[0] = (__force __le32)__raw_readl(nic_data->mcdi_smem + reg);
-}
-
-static inline void
-efx_mcdi_writed(struct efx_nic *efx, const efx_dword_t *value, unsigned reg)
-{
-	struct siena_nic_data *nic_data = efx->nic_data;
-	__raw_writel((__force u32)value->u32[0], nic_data->mcdi_smem + reg);
-}
-
 void efx_mcdi_init(struct efx_nic *efx)
 {
 	struct efx_mcdi_iface *mcdi;
@@ -84,8 +70,8 @@
 			    const u8 *inbuf, size_t inlen)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
-	unsigned pdu = MCDI_PDU(efx);
-	unsigned doorbell = MCDI_DOORBELL(efx);
+	unsigned pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx);
+	unsigned doorbell = FR_CZ_MC_TREG_SMEM + MCDI_DOORBELL(efx);
 	unsigned int i;
 	efx_dword_t hdr;
 	u32 xflags, seqno;
@@ -106,28 +92,29 @@
 			     MCDI_HEADER_SEQ, seqno,
 			     MCDI_HEADER_XFLAGS, xflags);
 
-	efx_mcdi_writed(efx, &hdr, pdu);
+	efx_writed(efx, &hdr, pdu);
 
 	for (i = 0; i < inlen; i += 4)
-		efx_mcdi_writed(efx, (const efx_dword_t *)(inbuf + i),
-				pdu + 4 + i);
+		_efx_writed(efx, *((__le32 *)(inbuf + i)), pdu + 4 + i);
+
+	/* Ensure the payload is written out before the header */
+	wmb();
 
 	/* ring the doorbell with a distinctive value */
-	EFX_POPULATE_DWORD_1(hdr, EFX_DWORD_0, 0x45789abc);
-	efx_mcdi_writed(efx, &hdr, doorbell);
+	_efx_writed(efx, (__force __le32) 0x45789abc, doorbell);
 }
 
 static void efx_mcdi_copyout(struct efx_nic *efx, u8 *outbuf, size_t outlen)
 {
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
-	unsigned int pdu = MCDI_PDU(efx);
+	unsigned int pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx);
 	int i;
 
 	BUG_ON(atomic_read(&mcdi->state) == MCDI_STATE_QUIESCENT);
 	BUG_ON(outlen & 3 || outlen >= 0x100);
 
 	for (i = 0; i < outlen; i += 4)
-		efx_mcdi_readd(efx, (efx_dword_t *)(outbuf + i), pdu + 4 + i);
+		*((__le32 *)(outbuf + i)) = _efx_readd(efx, pdu + 4 + i);
 }
 
 static int efx_mcdi_poll(struct efx_nic *efx)
@@ -135,7 +122,7 @@
 	struct efx_mcdi_iface *mcdi = efx_mcdi(efx);
 	unsigned int time, finish;
 	unsigned int respseq, respcmd, error;
-	unsigned int pdu = MCDI_PDU(efx);
+	unsigned int pdu = FR_CZ_MC_TREG_SMEM + MCDI_PDU(efx);
 	unsigned int rc, spins;
 	efx_dword_t reg;
 
@@ -161,7 +148,8 @@
 
 		time = get_seconds();
 
-		efx_mcdi_readd(efx, &reg, pdu);
+		rmb();
+		efx_readd(efx, &reg, pdu);
 
 		/* All 1's indicates that shared memory is in reset (and is
 		 * not a valid header). Wait for it to come out reset before
@@ -188,7 +176,7 @@
 			  respseq, mcdi->seqno);
 		rc = EIO;
 	} else if (error) {
-		efx_mcdi_readd(efx, &reg, pdu + 4);
+		efx_readd(efx, &reg, pdu + 4);
 		switch (EFX_DWORD_FIELD(reg, EFX_DWORD_0)) {
 #define TRANSLATE_ERROR(name)					\
 		case MC_CMD_ERR_ ## name:			\
@@ -222,21 +210,21 @@
 /* Test and clear MC-rebooted flag for this port/function */
 int efx_mcdi_poll_reboot(struct efx_nic *efx)
 {
-	unsigned int addr = MCDI_REBOOT_FLAG(efx);
+	unsigned int addr = FR_CZ_MC_TREG_SMEM + MCDI_REBOOT_FLAG(efx);
 	efx_dword_t reg;
 	uint32_t value;
 
 	if (efx_nic_rev(efx) < EFX_REV_SIENA_A0)
 		return false;
 
-	efx_mcdi_readd(efx, &reg, addr);
+	efx_readd(efx, &reg, addr);
 	value = EFX_DWORD_FIELD(reg, EFX_DWORD_0);
 
 	if (value == 0)
 		return 0;
 
 	EFX_ZERO_DWORD(reg);
-	efx_mcdi_writed(efx, &reg, addr);
+	efx_writed(efx, &reg, addr);
 
 	if (value == MC_STATUS_DWORD_ASSERT)
 		return -EINTR;