net: sfp: VSOL V2801F / CarlitoxxPro CPGOS03-0490 v2.0 workaround

Add a workaround for the detection of VSOL V2801F / CarlitoxxPro
CPGOS03-0490 v2.0 GPON module which CarlitoxxPro states needs single
byte I2C reads to the EEPROM.

Pali Rohár reports that he also has a CarlitoxxPro-based V2801F module,
which reports a manufacturer of "OEM". This manufacturer can't be
matched as it appears in many different modules, so also match the part
number too.

Reported-by: Thomas Schreiber <tschreibe@gmail.com>
Reported-by: Pali Rohár <pali@kernel.org>
Tested-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

@@ -219,6 +219,7 @@ struct sfp {
  struct sfp_bus *sfp_bus;
  struct phy_device *mod_phy;
  const struct sff_data *type;
+ size_t i2c_block_size;
  u32 max_power_mW;
 
  unsigned int (*get_state)(struct sfp *);
@@ -335,10 +336,19 @@ static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
  size_t len)
 {
  struct i2c_msg msgs[2];
- u8 bus_addr = a2 ? 0x51 : 0x50;
+ size_t block_size;
  size_t this_len;
+ u8 bus_addr;
  int ret;
 
+ if (a2) {
+ block_size = 16;
+ bus_addr = 0x51;
+ } else {
+ block_size = sfp->i2c_block_size;
+ bus_addr = 0x50;
+ }
+
  msgs[0].addr = bus_addr;
  msgs[0].flags = 0;
  msgs[0].len = 1;
@@ -350,8 +360,8 @@ static int sfp_i2c_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
 
  while (len) {
  this_len = len;
- if (this_len > 16)
- this_len = 16;
+ if (this_len > block_size)
+ this_len = block_size;
 
  msgs[1].len = this_len;
 
@@ -1632,6 +1642,28 @@ static int sfp_sm_mod_hpower(struct sfp *sfp, bool enable)
  return 0;
 }
 
+/* Some modules (Nokia 3FE46541AA) lock up if byte 0x51 is read as a
+ * single read. Switch back to reading 16 byte blocks unless we have
+ * a CarlitoxxPro module (rebranded VSOL V2801F). Even more annoyingly,
+ * some VSOL V2801F have the vendor name changed to OEM.
+ */
+static int sfp_quirk_i2c_block_size(const struct sfp_eeprom_base *base)
+{
+ if (!memcmp(base->vendor_name, "VSOL ", 16))
+ return 1;
+ if (!memcmp(base->vendor_name, "OEM ", 16) &&
+ !memcmp(base->vendor_pn, "V2801F ", 16))
+ return 1;
+
+ /* Some modules can't cope with long reads */
+ return 16;
+}
+
+static void sfp_quirks_base(struct sfp *sfp, const struct sfp_eeprom_base *base)
+{
+ sfp->i2c_block_size = sfp_quirk_i2c_block_size(base);
+}
+
 static int sfp_cotsworks_fixup_check(struct sfp *sfp, struct sfp_eeprom_id *id)
 {
  u8 check;
@@ -1673,14 +1705,20 @@ static int sfp_sm_mod_probe(struct sfp *sfp, bool report)
  u8 check;
  int ret;
 
- ret = sfp_read(sfp, false, 0, &id, sizeof(id));
+ /* Some modules (CarlitoxxPro CPGOS03-0490) do not support multibyte
+ * reads from the EEPROM, so start by reading the base identifying
+ * information one byte at a time.
+ */
+ sfp->i2c_block_size = 1;
+
+ ret = sfp_read(sfp, false, 0, &id.base, sizeof(id.base));
  if (ret < 0) {
  if (report)
  dev_err(sfp->dev, "failed to read EEPROM: %d\n", ret);
  return -EAGAIN;
  }
 
- if (ret != sizeof(id)) {
+ if (ret != sizeof(id.base)) {
  dev_err(sfp->dev, "EEPROM short read: %d\n", ret);
  return -EAGAIN;
  }
@@ -1719,6 +1757,21 @@ static int sfp_sm_mod_probe(struct sfp *sfp, bool report)
  }
  }
 
+ /* Apply any early module-specific quirks */
+ sfp_quirks_base(sfp, &id.base);
+
+ ret = sfp_read(sfp, false, SFP_CC_BASE + 1, &id.ext, sizeof(id.ext));
+ if (ret < 0) {
+ if (report)
+ dev_err(sfp->dev, "failed to read EEPROM: %d\n", ret);
+ return -EAGAIN;
+ }
+
+ if (ret != sizeof(id.ext)) {
+ dev_err(sfp->dev, "EEPROM short read: %d\n", ret);
+ return -EAGAIN;
+ }
+
  check = sfp_check(&id.ext, sizeof(id.ext) - 1);
  if (check != id.ext.cc_ext) {
  if (cotsworks) {