[PATCH] net/ixgbe: Retry SFP ID read field to handle misbehaving SFPs

[Wang, Haiyue]

> -----Original Message-----
> From: jeffd at silicom-usa.com <jeffd at silicom-usa.com>
> Sent: Tuesday, March 8, 2022 06:34
> To: dev at dpdk.org
> Cc: Stephen Douthit <stephend at silicom-usa.com>; Daly, Jeff <jeffd at silicom-usa.com>; Wang, Haiyue
> <haiyue.wang at intel.com>
> Subject: [PATCH] net/ixgbe: Retry SFP ID read field to handle misbehaving SFPs
> 
> From: Stephen Douthit <stephend at 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 <stephend at silicom-usa.com>
> Signed-off-by: Jeff Daly <jeffd at 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)


> +	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);

DEBUGOUT("status %d, SFF identifier 0x%x\n", status, identifier);

Since "#define IXGBE_SFF_IDENTIFIER_SFP	0x3" is hex value, and the ID is too simple.

> +		if (!status &&
> +		    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;
> +	}

This DEBUGOUT can be removed, it's redundant, every call for hw->phy.ops.read_i2c_eeprom
has added the DEBUOUT.

> 
>  	if (identifier != IXGBE_SFF_IDENTIFIER_SFP) {
>  		hw->phy.type = ixgbe_phy_sfp_unsupported;
> --
> 2.25.1