From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58A2C2877DE for ; Sun, 29 Mar 2026 18:23:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774808638; cv=none; b=nqSUDG2IPQXaezzuENf9B5jV0p6DCBpb59O/5EmvknAEoV7WcIIXmH8ywW9VTznFY7F0EcnQvOfbrbpIh0CneTnjTad1+Zb3RG36n3vsKa2oMsSEsmjPRrVtagSYRi7Yv71A+1RDuWyifRXKywIvcGAUAPhjNtv7TZE0D4rrgNM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774808638; c=relaxed/simple; bh=AoHDxgBxFj2ShgUSzbuVPL0dycvSGelmBMc8FaEWCnc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NuLukgaa+yUWulFI52Zusd4yaCLLn8YAFKb63XcubdhxEzdya2kE+C9drjzlcOej1DMs0pqwVNIobAmzWIPMfFGWgdez2Xw3w8iXteP8dP7q6vfJ6lefEO+jboJj+betMVRX34cEx60v1x94o+8lLBGE7VcQW6ejS17mQrXdL0s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=OI9CE+1j; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="OI9CE+1j" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=qGzDB+BbAy2UxWoOKWueCLa/Ve0k5Xt432NyksbrD1U=; b=OI9CE+1jdkOigebK4UrGva7oIH 3kb6rNiaKlWyPv2pDJn6V1iQL+x3Xtk85WTKuiPDyEx6wH4eVUKwm1tQU6SUbEkj2LpFy75BYdzXI ij5MXbjcz8hCG+Nkh+/BOZUT8UpGncxn5isVX7KDE8IIEyltT21JtcHm9VLbkg/JD4+wwEr+bL3fc 0vmnLgqW07tzcvAL090WEePlhMqKqWKqBvYvGtpvt95cdj2thxGnqttJjOTydf0ENTF0IxPYP0Dts +49KfUhFq9JwHkJnQACDdjYh6cLKTSuBsyROp4wJcEQJ6VYOfckxw1Zp6zWc9PyDBYOhot1H7uaJH tX13naQg==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:49410) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1w6unc-000000008Ak-0F8p; Sun, 29 Mar 2026 19:23:48 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1w6unY-000000001vr-31Tz; Sun, 29 Mar 2026 19:23:44 +0100 Date: Sun, 29 Mar 2026 19:23:44 +0100 From: "Russell King (Oracle)" To: Jakub Kicinski Cc: Andrew Lunn , Alexandre Torgue , Andrew Lunn , "David S. Miller" , Eric Dumazet , linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, netdev@vger.kernel.org, Ong Boon Leong , Paolo Abeni Subject: Re: [PATCH net-next 01/10] net: stmmac: fix TSO support when some channels have TBS available Message-ID: References: <20260329104223.358351ee@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260329104223.358351ee@kernel.org> Sender: Russell King (Oracle) On Sun, Mar 29, 2026 at 10:42:23AM -0700, Jakub Kicinski wrote: > On Sun, 29 Mar 2026 10:40:43 +0100 Russell King (Oracle) wrote: > > On Sat, Mar 28, 2026 at 09:36:41PM +0000, Russell King (Oracle) wrote: > > > According to the STM32MP25xx manual, which is dwmac v5.3, TBS (time > > > based scheduling) is not permitted for channels which have hardware > > > TSO enabled. Intel's commit 5e6038b88a57 ("net: stmmac: fix TSO and > > > TBS feature enabling during driver open") concurs with this, but it > > > is incomplete. > > > > > > This commit avoids enabling TSO support on the channels which have > > > TBS available, which, as far as the hardware is concerned, means we > > > do not set the TSE bit in the DMA channel's transmit control register. > > > > > > However, the net device's features apply to all queues(channels), which > > > means these channels may still be handed TSO skbs to transmit, and the > > > driver will pass them to stmmac_tso_xmit(). This will generate the > > > descriptors for TSO, even though the channel has the TSE bit clear. > > > > > > Fix this by checking whether the queue(channel) has TBS available, > > > and if it does, fall back to software GSO support. > > > > This is sufficient for the immediate issue of fixing the patch below, > > but I think there's another issue that also needs fixing here. > > > > TSO requires the hardware to support checksum offload, and there is > > a comment in the driver: > > > > /* DWMAC IPs can be synthesized to support tx coe only for a few tx > > * queues. In that case, checksum offloading for those queues that don't > > * support tx coe needs to fallback to software checksum calculation. > > * > > * Packets that won't trigger the COE e.g. most DSA-tagged packets will > > * also have to be checksummed in software. > > */ > > > > So, it seems at the very least we need to add a check (in a subsequent > > patch) for priv->plat->tx_queues_cfg[queue].coe_unsupported to > > stmmac_channel_tso_permitted(). > > > > I'm also wondering about the stmmac_has_ip_ethertype() thing, which > > checks whether the skb can be checksummed by the hardware, and how that > > interacts with TSO, and whether that's yet another hole that needs > > plugging. > > If the driver "un-advertises" checksum offload accordingly the core > should automatically clear TSO feature. Ah, yes, it's in harmonize_features(). However, I think that stmmac_has_ip_ethertype() is tighter than the checks that harmonize_features() does. stmmac_has_ip_ethertype(): int depth = 0; __be16 proto; proto = __vlan_get_protocol(skb, eth_header_parse_protocol(skb), &depth); return (depth <= ETH_HLEN) && (proto == htons(ETH_P_IP) || proto == htons(ETH_P_IPV6)); If I'm reading this correctly, then eth_header_parse_protocol(skb) will return the contents of the ethernet header protocol field. __vlan_get_protocol() will then return: - that protocol if it is not a vlan (0x8100 or 0x88A8) with depth set to skb->mac_len, which should be ETH_HLEN here. - the protocol below the vlan headers, in which case depth will be > ETH_HLEN Unless I've missed something, that basically means that the __vlan_get_protocol() is pointless there, and the entire function could just be checking that eth_header_parse_protocol(skb) returns IP or IPv6. Isn't it the case that skb->protocol should be the same as eth_header_parse_protocol(skb) for a packet being transmitted at the point that .ndo_features_check() or .ndo_start_xmit() is called? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!