On Fri, May 31, 2019 at 01:18:03PM -0600, Robert Hancock wrote:
> The SFP driver was reading up to 256 bytes of I2C data from the SFP
> module in a single chunk. However, some I2C controllers do not support
> reading that many bytes in a single transaction. Change to use a more
> compatible 16-byte chunk size, since this is not performance critical.
This is the wrong place to fix the problem. We still end up reading
more than 16 bytes with this approach. I already have a patch fixing
this the right way, which is in the queue to be sent.
>
> Signed-off-by: Robert Hancock <hanc...@sedsystems.ca>
> ---
> drivers/net/phy/sfp.c | 38 ++++++++++++++++++++++++--------------
> 1 file changed, 24 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
> index 6b6c83d..23a40a7 100644
> --- a/drivers/net/phy/sfp.c
> +++ b/drivers/net/phy/sfp.c
> @@ -1651,7 +1651,7 @@ static int sfp_module_info(struct sfp *sfp, struct
> ethtool_modinfo *modinfo)
> static int sfp_module_eeprom(struct sfp *sfp, struct ethtool_eeprom *ee,
> u8 *data)
> {
> - unsigned int first, last, len;
> + unsigned int first, last;
> int ret;
>
> if (ee->len == 0)
> @@ -1659,26 +1659,36 @@ static int sfp_module_eeprom(struct sfp *sfp, struct
> ethtool_eeprom *ee,
>
> first = ee->offset;
> last = ee->offset + ee->len;
> - if (first < ETH_MODULE_SFF_8079_LEN) {
> - len = min_t(unsigned int, last, ETH_MODULE_SFF_8079_LEN);
> - len -= first;
>
> - ret = sfp_read(sfp, false, first, data, len);
> + while (first < last) {
> + bool a2;
> + unsigned int this_addr, len;
> +
> + if (first < ETH_MODULE_SFF_8079_LEN) {
> + len = min_t(unsigned int, last,
> + ETH_MODULE_SFF_8079_LEN);
> + len -= first;
> + a2 = false;
> + this_addr = first;
> + } else {
> + len = min_t(unsigned int, last,
> + ETH_MODULE_SFF_8472_LEN);
> + len -= first;
> + a2 = true;
> + this_addr = first - ETH_MODULE_SFF_8079_LEN;
> + }
> + /* Some I2C adapters cannot read 256 bytes in a single read.
> + * Use a smaller chunk size to ensure we are within limits.
> + */
> + len = min_t(unsigned int, len, 16);
> +
> + ret = sfp_read(sfp, a2, this_addr, data, len);
> if (ret < 0)
> return ret;
>
> first += len;
> data += len;
> }
> - if (first < ETH_MODULE_SFF_8472_LEN && last > ETH_MODULE_SFF_8079_LEN) {
> - len = min_t(unsigned int, last, ETH_MODULE_SFF_8472_LEN);
> - len -= first;
> - first -= ETH_MODULE_SFF_8079_LEN;
> -
> - ret = sfp_read(sfp, true, first, data, len);
> - if (ret < 0)
> - return ret;
> - }
> return 0;
> }
>
> --
> 1.8.3.1
>
>
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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