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smsc911x: enforce read-after-write timing restriction on eeprom access

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The LAN911x datasheet specifies a minimum delay of 45ns between a write
of E2P_DATA and any read.  This patch adds a single dummy read of
BYTE_TEST to enforce this timing constraint.

Signed-off-by: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Steve Glendinning 2009-03-26 07:14:36 +00:00 committed by David S. Miller
parent 54dc79fe0d
commit 58add9fc02
1 changed files with 5 additions and 0 deletions
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5
drivers/net/smsc911x.c
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@ -1680,6 +1680,7 @@ static int smsc911x_eeprom_write_location(struct smsc911x_data *pdata,
u8 address, u8 data)
{
u32 op = E2P_CMD_EPC_CMD_ERASE_ | address;
u32 temp;
int ret;
SMSC_TRACE(DRV, "address 0x%x, data 0x%x", address, data);
@ -1688,6 +1689,10 @@ static int smsc911x_eeprom_write_location(struct smsc911x_data *pdata,
if (!ret) {
op = E2P_CMD_EPC_CMD_WRITE_ | address;
smsc911x_reg_write(pdata, E2P_DATA, (u32)data);
/* Workaround for hardware read-after-write restriction */
temp = smsc911x_reg_read(pdata, BYTE_TEST);
ret = smsc911x_eeprom_send_cmd(pdata, op);
}