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r6040: add delays in MDIO read/write polling loops 

On newer and faster machines (Vortex X86DX) using the r6040 driver, it
was noticed that the driver was returning an error during probing traced
down to being the MDIO bus probing and the inability to complete a MDIO
read operation in time. It turns out that the MDIO operations on these
faster machines usually complete after ~2140 iterations which is bigger
than 2048 (MAC_DEF_TIMEOUT) and results in spurious timeouts depending
on the system load.

Update r6040_phy_read() and r6040_phy_write() to include a 1
micro second delay in each busy-looping iteration of the loop which is a
much safer operation than incrementing MAC_DEF_TIMEOUT.

Reported-by: Nils Koehler <nils.koehler@ibt-interfaces.de>
Reported-by: Daniel Goertzen <daniel.goertzen@gmail.com>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Fainelli 2014-01-15 13:04:25 -08:00 committed by David S. Miller
parent 2c0057dec9
commit 4f8d9f3ce0
1 changed files with 2 additions and 0 deletions
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2
drivers/net/ethernet/rdc/r6040.c
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@ -221,6 +221,7 @@ static int r6040_phy_read(void __iomem *ioaddr, int phy_addr, int reg)
cmd = ioread16(ioaddr + MMDIO); cmd = ioread16(ioaddr + MMDIO);
if (!(cmd & MDIO_READ)) if (!(cmd & MDIO_READ))
break; break;
udelay(1);
} }
if (limit < 0) if (limit < 0)
@ -244,6 +245,7 @@ static int r6040_phy_write(void __iomem *ioaddr,
cmd = ioread16(ioaddr + MMDIO); cmd = ioread16(ioaddr + MMDIO);
if (!(cmd & MDIO_WRITE)) if (!(cmd & MDIO_WRITE))
break; break;
udelay(1);
} }
return (limit < 0) ? -ETIMEDOUT : 0; return (limit < 0) ? -ETIMEDOUT : 0;