From: Russell King Date: Sun, 2 Jun 2019 14:13:00 +0000 (+0100) Subject: net: sfp: read eeprom in maximum 16 byte increments X-Git-Tag: v4.14.125~29 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c77b064face108a3eff1d22aa823ffdbdb6acba9;p=users%2Fdwmw2%2Flinux.git net: sfp: read eeprom in maximum 16 byte increments [ 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 Reviewed-by: Andrew Lunn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c index 5ab725a571a84..2dcb25aa0452d 100644 --- a/drivers/net/phy/sfp.c +++ b/drivers/net/phy/sfp.c @@ -168,6 +168,7 @@ static int sfp__i2c_read(struct i2c_adapter *i2c, u8 bus_addr, u8 dev_addr, void *buf, size_t len) { struct i2c_msg msgs[2]; + size_t this_len; int ret; msgs[0].addr = bus_addr; @@ -179,11 +180,26 @@ static int sfp__i2c_read(struct i2c_adapter *i2c, u8 bus_addr, u8 dev_addr, msgs[1].len = len; msgs[1].buf = buf; - ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs)); - if (ret < 0) - return ret; + while (len) { + this_len = len; + if (this_len > 16) + this_len = 16; + + msgs[1].len = this_len; + + ret = i2c_transfer(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 ret == ARRAY_SIZE(msgs) ? len : 0; + return msgs[1].buf - (u8 *)buf; } static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 addr, void *buf,