> -----Original Message-----
> From: je...@silicom-usa.com <je...@silicom-usa.com>
> Sent: Tuesday, March 8, 2022 06:34
> To: dev@dpdk.org
> Cc: Stephen Douthit <steph...@silicom-usa.com>; Daly, Jeff
> <je...@silicom-usa.com>; Wang, Haiyue
> <haiyue.w...@intel.com>
> Subject: [PATCH] net/ixgbe: Retry SFP ID read field to handle misbehaving SFPs
>
> From: Stephen Douthit <steph...@silicom-usa.com>
>
> Some XGS-PON SFPs have been observed ACKing I2C reads and returning
> uninitialized garbage while their uC boots. This can lead to the SFP ID
> code marking an otherwise working SFP module as unsupported if a bogus
> ID value is read while its internal PHY/microcontroller is still
> booting.
>
> Retry the ID read several times looking not just for NAK, but also for a
> valid ID field.
>
> Since the device isn't NAKing the trasanction the existing longer retry
> code in ixgbe_read_i2c_byte_generic_int() doesn't apply here.
>
> Signed-off-by: Stephen Douthit <steph...@silicom-usa.com>
> Signed-off-by: Jeff Daly <je...@silicom-usa.com>
> ---
> drivers/net/ixgbe/base/ixgbe_phy.c | 31 ++++++++++++++++++++++++++----
> 1 file changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ixgbe/base/ixgbe_phy.c
> b/drivers/net/ixgbe/base/ixgbe_phy.c
> index d8d51d2c3f..27bce066a1 100644
> --- a/drivers/net/ixgbe/base/ixgbe_phy.c
> +++ b/drivers/net/ixgbe/base/ixgbe_phy.c
> @@ -1275,6 +1275,7 @@ s32 ixgbe_identify_sfp_module_generic(struct ixgbe_hw
> *hw)
> u8 cable_tech = 0;
> u8 cable_spec = 0;
> u16 enforce_sfp = 0;
> + u8 id_reads;
"u8 retries" is a better name, I think, to match the patch title.
>
> DEBUGFUNC("ixgbe_identify_sfp_module_generic");
>
> @@ -1287,12 +1288,34 @@ s32 ixgbe_identify_sfp_module_generic(struct ixgbe_hw
> *hw)
> /* LAN ID is needed for I2C access */
> hw->mac.ops.set_lan_id(hw);
>
> - status = hw->phy.ops.read_i2c_eeprom(hw,
> - IXGBE_SFF_IDENTIFIER,
> - &identifier);
> + /* Need to check this a couple of times for a sane value.
> + *
> + * SFPs that have a uC slaved to the I2C bus (vs. a dumb EEPROM) can be
> + * poorly designed such that they will ACK I2C reads and return
> + * whatever bogus data is in the SRAM (or whatever is backing the target
> + * device) before things are truly initialized.
> + *
> + * In a perfect world devices would NAK I2C requests until they were
> + * sane, but here we are.
> + *
> + * Give such devices a couple tries to get their act together before
> + * marking the device as unsupported.
> + */
> + for (id_reads = 0; id_reads < 5; id_reads++) {
> + status = hw->phy.ops.read_i2c_eeprom(hw,
> + IXGBE_SFF_IDENTIFIER,
> + &identifier);
>
> - if (status != IXGBE_SUCCESS)
> + DEBUGOUT("status %d, id %d\n", status, identifier);
> + if (!status &&
> + identifier == IXGBE_SFF_IDENTIFIER_SFP)
Let's not assume the ' IXGBE_SUCCESS' is '0', so change it to:
if (status == IXGBE_SUCCESS &&
identifier == IXGBE_SFF_IDENTIFIER_SFP)
> + break;
> + }
> +
> + if (status != IXGBE_SUCCESS) {
> + DEBUGOUT("Failed SFF ID read (%d attempts)\n", id_reads);
> goto err_read_i2c_eeprom;
> + }
>
> if (identifier != IXGBE_SFF_IDENTIFIER_SFP) {
> hw->phy.type = ixgbe_phy_sfp_unsupported;
> --
> 2.25.1
