On 08/27/2018 03:26 PM, Russell King - ARM Linux wrote: > On Mon, Aug 27, 2018 at 01:03:42PM -0700, Florian Fainelli wrote: >> Enable the SFP connected to port 5 of the switch and wire up all GPIOs >> to the SFP cage. Because of a hardware limitation of the i2c controller >> on the iProc SoCs which prevents large i2c (> 256 bytes) transactions to >> work, we use the i2c-gpio interface instead, which does not have that >> limitation. This allows us to read the SFP module EEPROM, which would >> not be possible otherwise since it exceeds that size during a single >> read transfer. > > We shouldn't exceed 256 bytes, since 256 bytes is the "page" size > of the EEPROM. The most that we read in one block is either > ETH_MODULE_SFF_8079_LEN or (ETH_MODULE_SFF_8472_LEN - > ETH_MODULE_SFF_8079_LEN), both of which result in no more than 256 > byte reads.
You are right, I got things mixed up here, the controller's limitation is actually 63 bytes per transfer, I will be rewording the commit message accordingly. -- Florian
