From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6EEECA9EC8 for ; Fri, 18 Oct 2019 00:33:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A37A421852 for ; Fri, 18 Oct 2019 00:33:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392856AbfJRAdc (ORCPT ); Thu, 17 Oct 2019 20:33:32 -0400 Received: from gate.crashing.org ([63.228.1.57]:47116 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728419AbfJRAdc (ORCPT ); Thu, 17 Oct 2019 20:33:32 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x9I0Wvrx022950; Thu, 17 Oct 2019 19:32:58 -0500 Message-ID: Subject: Re: [PATCH v2] ftgmac100: Disable HW checksum generation on AST2500 From: Benjamin Herrenschmidt To: Vijay Khemka , "David S. Miller" , Kate Stewart , Sven Van Asbroeck , Mark Brown , Bhupesh Sharma , YueHaibing , Mauro Carvalho Chehab , Luis Chamberlain , Thomas Gleixner , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Cc: "openbmc @ lists . ozlabs . org" , "joel@jms.id.au" , "linux-aspeed@lists.ozlabs.org" , Sai Dasari Date: Fri, 18 Oct 2019 11:32:57 +1100 In-Reply-To: <9AA81274-01F2-4803-8905-26F0521486CE@fb.com> References: <20191011213027.2110008-1-vijaykhemka@fb.com> <3a1176067b745fddfc625bbd142a41913ee3e3a1.camel@kernel.crashing.org> <0C0BC813-5A84-403F-9C48-9447AAABD867@fb.com> <071cf1eeefcbfc14633a13bc2d15ad7392987a88.camel@kernel.crashing.org> <9AA81274-01F2-4803-8905-26F0521486CE@fb.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-10-18 at 00:06 +0000, Vijay Khemka wrote: > > > 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. > > My understanding was when we enable NETIF_F_HW_CSUM means network > stack enables HW checksum and doesn't calculate SW checksum. But as per > this supported types HW checksum are used only for IPV4 and not for IPV6 even > though driver enabled NETIF_F_HW_CSUM. For IPV6 it is always a SW generated > checksum, please correct me here. Have you actually read the comments in skbuff.h that I pointed you to ? And the rest of my email for that matter ? > 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 */ > > > > > > > > >