Commit bab4057c authored by Russell King's avatar Russell King Committed by Greg Kroah-Hartman

net: sfp: read eeprom in maximum 16 byte increments

[ Upstream commit 28e74a7c ]

Some SFP modules do not like reads longer than 16 bytes, so read the
EEPROM in chunks of 16 bytes at a time.  This behaviour is not specified
in the SFP MSAs, which specifies:

 "The serial interface uses the 2-wire serial CMOS E2PROM protocol
  defined for the ATMEL AT24C01A/02/04 family of components."

and

 "As long as the SFP+ receives an acknowledge, it shall serially clock
  out sequential data words. The sequence is terminated when the host
  responds with a NACK and a STOP instead of an acknowledge."

We must avoid breaking a read across a 16-bit quantity in the diagnostic
page, thankfully all 16-bit quantities in that page are naturally
aligned.
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: default avatarAndrew Lunn <andrew@lunn.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 023998c9
......@@ -281,6 +281,7 @@ static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
{
struct i2c_msg msgs[2];
u8 bus_addr = a2 ? 0x51 : 0x50;
size_t this_len;
int ret;
msgs[0].addr = bus_addr;
......@@ -292,11 +293,26 @@ static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
msgs[1].len = len;
msgs[1].buf = buf;
ret = i2c_transfer(sfp->i2c, msgs, ARRAY_SIZE(msgs));
if (ret < 0)
return ret;
while (len) {
this_len = len;
if (this_len > 16)
this_len = 16;
return ret == ARRAY_SIZE(msgs) ? len : 0;
msgs[1].len = this_len;
ret = i2c_transfer(sfp->i2c, msgs, ARRAY_SIZE(msgs));
if (ret < 0)
return ret;
if (ret != ARRAY_SIZE(msgs))
break;
msgs[1].buf += this_len;
dev_addr += this_len;
len -= this_len;
}
return msgs[1].buf - (u8 *)buf;
}
static int sfp_i2c_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment