From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Date: Fri, 18 Oct 2019 10:14:47 +1100 Subject: [PATCH v2] ftgmac100: Disable HW checksum generation on AST2500 In-Reply-To: <0C0BC813-5A84-403F-9C48-9447AAABD867@fb.com> References: <20191011213027.2110008-1-vijaykhemka@fb.com> <3a1176067b745fddfc625bbd142a41913ee3e3a1.camel@kernel.crashing.org> <0C0BC813-5A84-403F-9C48-9447AAABD867@fb.com> Message-ID: <071cf1eeefcbfc14633a13bc2d15ad7392987a88.camel@kernel.crashing.org> List-Id: To: linux-aspeed@lists.ozlabs.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, 2019-10-17 at 22:01 +0000, Vijay Khemka wrote: > > ?On 10/16/19, 6:29 PM, "Benjamin Herrenschmidt" wrote: > > On Fri, 2019-10-11 at 14:30 -0700, Vijay Khemka wrote: > > HW checksum generation is not working for AST2500, specially with > > IPV6 > > over NCSI. All TCP packets with IPv6 get dropped. By disabling this > > it works perfectly fine with IPV6. As it works for IPV4 so enabled > > hw checksum back for IPV4. > > > > Verified with IPV6 enabled and can do ssh. > > So while this probably works, I don't think this is the right > approach, at least according to the comments in skbuff.h > > This is not a matter of unsupported csum, it is broken hw csum. > That's why we disable hw checksum. My guess is once we disable > Hw checksum, it will use sw checksum. So I am just disabling hw > Checksum. I don't understand what you are saying. You reported a problem with IPV6 checksums generation. The HW doesn't support it. What's "not a matter of unsupported csum" ? Your patch uses a *deprecated* bit to tell the network stack to only do HW checksum generation on IPV4. This bit is deprecated for a reason, again, see skbuff.h. The right approach, *which the driver already does*, is to tell the stack that we support HW checksuming using NETIF_F_HW_CSUM, and then, in the transmit handler, to call skb_checksum_help() to have the SW calculate the checksum if it's not a supported type. This is exactly what ftgmac100_prep_tx_csum() does. It only enables HW checksum generation on supported types and uses skb_checksum_help() otherwise, supported types being protocol ETH_P_IP and IP protocol being raw IP, TCP and UDP. So this *should* have fallen back to SW for IPV6. So either something in my code there is making an incorrect assumption, or something is broken in skb_checksum_help() for IPV6 (which I somewhat doubt) or something else I can't think of, but setting a *deprecated* flag is definitely not the right answer, neither is completely disabling HW checksumming. So can you investigate what's going on a bit more closely please ? I can try myself, though I have very little experience with IPV6 and probably won't have time before next week. Cheers, Ben. > The driver should have handled unsupported csum via SW fallback > already in ftgmac100_prep_tx_csum() > > Can you check why this didn't work for you ? > > Cheers, > Ben. > > > Signed-off-by: Vijay Khemka > > --- > > Changes since v1: > > Enabled IPV4 hw checksum generation as it works for IPV4. > > > > drivers/net/ethernet/faraday/ftgmac100.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/net/ethernet/faraday/ftgmac100.c > > b/drivers/net/ethernet/faraday/ftgmac100.c > > index 030fed65393e..0255a28d2958 100644 > > --- a/drivers/net/ethernet/faraday/ftgmac100.c > > +++ b/drivers/net/ethernet/faraday/ftgmac100.c > > @@ -1842,8 +1842,19 @@ static int ftgmac100_probe(struct > > platform_device *pdev) > > /* AST2400 doesn't have working HW checksum generation */ > > if (np && (of_device_is_compatible(np, "aspeed,ast2400-mac"))) > > netdev->hw_features &= ~NETIF_F_HW_CSUM; > > + > > + /* AST2500 doesn't have working HW checksum generation for IPV6 > > + * but it works for IPV4, so disabling hw checksum and enabling > > + * it for only IPV4. > > + */ > > + if (np && (of_device_is_compatible(np, "aspeed,ast2500-mac"))) > > { > > + netdev->hw_features &= ~NETIF_F_HW_CSUM; > > + netdev->hw_features |= NETIF_F_IP_CSUM; > > + } > > + > > if (np && of_get_property(np, "no-hw-checksum", NULL)) > > - netdev->hw_features &= ~(NETIF_F_HW_CSUM | > > NETIF_F_RXCSUM); > > + netdev->hw_features &= ~(NETIF_F_HW_CSUM | > > NETIF_F_RXCSUM > > + | NETIF_F_IP_CSUM); > > netdev->features |= netdev->hw_features; > > > > /* register network device */ > > >