[PATCH] r8169: quirk for the 8110sb on arm platform

[Francois Romieu]

Inverting the write ordering of the TxDescAddr{High/Low} registers
suffices to trigger a sabbat of PCI errors which make the device
completely dysfunctional. The issue has not been reported on a
different platform.

Switching from MMIO accesses to I/O ones as done in Realtek's
own driver fixes (papers over ?) the bug as well but I am not
thrilled to see everyone pay the I/O price for an obscure bug.

This is the minimal change to handle the issue.

Signed-off-by: Francois Romieu <romieu@xxxxxxxxxxxxx>
Reported-by: Lennert Buytenhek <buytenh@xxxxxxxxxxxxxx>
---
 drivers/net/r8169.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index 7ab79db..582b116 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -1868,10 +1868,15 @@ rtl8169_hw_start(struct net_device *dev)
 	 */
 	RTL_W16(IntrMitigate, 0x0000);
 
-	RTL_W32(TxDescStartAddrLow, ((u64) tp->TxPhyAddr & DMA_32BIT_MASK));
+	/*
+	 * Magic spell: some iop3xx ARM board needs the TxDescAddrHigh
+	 * register to be written before TxDescAddrLow to work.
+	 * Switching from MMIO to I/O access fixes the issue as well.
+	 */
 	RTL_W32(TxDescStartAddrHigh, ((u64) tp->TxPhyAddr >> 32));
-	RTL_W32(RxDescAddrLow, ((u64) tp->RxPhyAddr & DMA_32BIT_MASK));
+	RTL_W32(TxDescStartAddrLow, ((u64) tp->TxPhyAddr & DMA_32BIT_MASK));
 	RTL_W32(RxDescAddrHigh, ((u64) tp->RxPhyAddr >> 32));
+	RTL_W32(RxDescAddrLow, ((u64) tp->RxPhyAddr & DMA_32BIT_MASK));
 	RTL_W8(ChipCmd, CmdTxEnb | CmdRxEnb);
 	RTL_W8(Cfg9346, Cfg9346_Lock);
 
-- 
1.4.2.4


--HlL+5n6rz5pIUxbD--
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