From 28e74a7cfd6403f0d1c0f8b10b45d6fae37b227e Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Sun, 2 Jun 2019 15:13:00 +0100
Subject: [PATCH] net: sfp: read eeprom in maximum 16 byte increments
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>
---
drivers/net/phy/sfp.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index d4635c2178d14..71812be0ac645 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -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,
--
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