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[146.241.230.60]) by smtp.gmail.com with ESMTPSA id t18-20020a05600c199200b0040ecdd672fasm213707wmq.13.2024.02.05.07.49.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Feb 2024 07:49:34 -0800 (PST) Message-ID: Subject: Re: [PATCH v2 1/6] net: wan: Add support for QMC HDLC From: Paolo Abeni To: Herve Codina Date: Mon, 05 Feb 2024 16:49:33 +0100 In-Reply-To: <20240205152208.73535549@bootlin.com> References: <20240130084035.115086-1-herve.codina@bootlin.com> <20240130084035.115086-2-herve.codina@bootlin.com> <20240205152208.73535549@bootlin.com> Autocrypt: addr=pabeni@redhat.com; prefer-encrypt=mutual; keydata=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 7ZxN9ZsDL38qVIuFkSpgMZCiUHdxBC11J8nbBSLlpnc924UAyr5XrGA99 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 iWjoCy8L35zPqR5TV+f5WR5hTVCqmLHSgm1jxwKhPg9L+GfuE4d0SWd84y 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 sD2W1U7eyLdm/jCgticGDsRtweytsgCSYfbz0gdgUuL3EBYN3JLbAU+UZpy 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 User-Agent: Evolution 3.50.3 (3.50.3-1.fc39) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Lunn , Vadim Fedorenko , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Mark Brown , Thomas Petazzoni , Jakub Kicinski , linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, 2024-02-05 at 15:22 +0100, Herve Codina wrote: > Hi Paolo, >=20 > On Thu, 01 Feb 2024 12:41:32 +0100 > Paolo Abeni wrote: >=20 > [...] > > > +static inline struct qmc_hdlc *netdev_to_qmc_hdlc(struct net_device = *netdev) > > > +{ > > > +=09return dev_to_hdlc(netdev)->priv; > > > +} =20 > >=20 > > Please, no 'inline' function in c files. You could move this function > > and the struct definition into a new, local, header file. >=20 > 'inline' function specifier will be removed in the next iteration on the = series. >=20 > >=20 > > > +static int qmc_hdlc_recv_queue(struct qmc_hdlc *qmc_hdlc, struct qmc= _hdlc_desc *desc, size_t size); > > > + > > > +#define QMC_HDLC_RX_ERROR_FLAGS (QMC_RX_FLAG_HDLC_OVF | \ > > > +=09=09=09=09 QMC_RX_FLAG_HDLC_UNA | \ > > > +=09=09=09=09 QMC_RX_FLAG_HDLC_ABORT | \ > > > +=09=09=09=09 QMC_RX_FLAG_HDLC_CRC) > > > + > > > +static void qmc_hcld_recv_complete(void *context, size_t length, uns= igned int flags) > > > +{ > > > +=09struct qmc_hdlc_desc *desc =3D context; > > > +=09struct net_device *netdev =3D desc->netdev; > > > +=09struct qmc_hdlc *qmc_hdlc =3D netdev_to_qmc_hdlc(netdev); > > > +=09int ret; =20 > >=20 > > Please, respect the reverse x-mas tree order for local variable > > definition. >=20 > desc depends on context, netdev depends on desc and qmc_hdlc depends on n= etdev. > I think the declaration order is correct here even it doesn't respect the= reverse > x-mas tree. >=20 > [...] > > > +static netdev_tx_t qmc_hdlc_xmit(struct sk_buff *skb, struct net_dev= ice *netdev) > > > +{ > > > +=09struct qmc_hdlc *qmc_hdlc =3D netdev_to_qmc_hdlc(netdev); > > > +=09struct qmc_hdlc_desc *desc; > > > +=09unsigned long flags; > > > +=09int ret; > > > + > > > +=09spin_lock_irqsave(&qmc_hdlc->tx_lock, flags); > > > +=09desc =3D &qmc_hdlc->tx_descs[qmc_hdlc->tx_out]; > > > +=09if (WARN_ONCE(!desc->skb, "No tx descriptors available\n")) { > > > +=09=09/* Should never happen. > > > +=09=09 * Previous xmit should have already stopped the queue. > > > +=09=09 */ > > > +=09=09netif_stop_queue(netdev); > > > +=09=09spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags); > > > +=09=09return NETDEV_TX_BUSY; > > > +=09} > > > +=09spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags); > > > + > > > +=09desc->netdev =3D netdev; > > > +=09desc->dma_size =3D skb->len; > > > +=09desc->skb =3D skb; > > > +=09ret =3D qmc_hdlc_xmit_queue(qmc_hdlc, desc); > > > +=09if (ret) { > > > +=09=09desc->skb =3D NULL; /* Release the descriptor */ > > > +=09=09if (ret =3D=3D -EBUSY) { > > > +=09=09=09netif_stop_queue(netdev); > > > +=09=09=09return NETDEV_TX_BUSY; > > > +=09=09} > > > +=09=09dev_kfree_skb(skb); > > > +=09=09netdev->stats.tx_dropped++; > > > +=09=09return NETDEV_TX_OK; > > > +=09} > > > + > > > +=09qmc_hdlc->tx_out =3D (qmc_hdlc->tx_out + 1) % ARRAY_SIZE(qmc_hdlc= ->tx_descs); > > > + > > > +=09spin_lock_irqsave(&qmc_hdlc->tx_lock, flags); > > > +=09if (qmc_hdlc->tx_descs[qmc_hdlc->tx_out].skb) > > > +=09=09netif_stop_queue(netdev); > > > +=09spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags); =20 > >=20 > > The locking schema is quite bad, as the drivers acquires and releases 3 > > locks for each tx packet. You could improve that using the qmc_chan- > > > tx_lock to protect the whole qmc_hdlc_xmit() function, factoring out = a =20 > > lockless variant of qmc_hdlc_xmit_queue(),=C2=A0and using it here. >=20 > I will change on next iteration and keep 2 lock/unlock instead of 3: > - one in qmc_hdlc_xmit() > - one in qmc_hdlc_xmit_complete()=20 > to protect the descriptors accesses. >=20 > >=20 > > In general is quite bad that the existing infra does not allow > > leveraging NAPI. Have you considered expanding the QMC to accomodate > > such user? >=20 > I cannot mask/unmask the 'end of transfer' interrupt. > Indeed, other streams use this interrupt among them audio streams and so > masking the interrupt for HDLC data will also mask the interrupt for audi= o > data. Uhm... I fear the above makes the available options list empty :( > At the HDLC driver level, the best I can to is to store a queue of comple= te > HDLC skbs (queue filled on interrupts) and send them to the network stack > when the napi poll() is called. >=20 > I am not sure that this kind of queue (additional level between always > enabled interrupts and the network stack) makes sense. >=20 > Do you have any opinion about this additional queue management for NAPI > support? With such idea in place, what HDLC-level data will be accessed by the napi context? The RX interrupts will remain unmasked after the interrupt and before the napi poll right? That would be problematic/could cause drop if the ingress pkt/interrupt rate will be higher that what the napi could process - and that in turn could bring back old bad livelock times :( Cheers, Paolo