From: Russell King rmk+kernel@armlinux.org.uk
[ Upstream commit 28e74a7cfd6403f0d1c0f8b10b45d6fae37b227e ]
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: Russell King rmk+kernel@armlinux.org.uk Reviewed-by: Andrew Lunn andrew@lunn.ch Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/phy/sfp.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
--- a/drivers/net/phy/sfp.c +++ b/drivers/net/phy/sfp.c @@ -281,6 +281,7 @@ static int sfp_i2c_read(struct sfp *sfp, { 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, 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,