From patchwork Wed Dec 9 18:47:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Willy Tarreau X-Patchwork-Id: 341719 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT 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 880CAC433FE for ; Wed, 9 Dec 2020 18:48:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BC292228A for ; Wed, 9 Dec 2020 18:48:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387459AbgLISsv (ORCPT ); Wed, 9 Dec 2020 13:48:51 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:48315 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733278AbgLISsv (ORCPT ); Wed, 9 Dec 2020 13:48:51 -0500 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 0B9IlnlW016513; Wed, 9 Dec 2020 19:47:49 +0100 From: Willy Tarreau To: Jakub Kicinski Cc: netdev@vger.kernel.org, David Miller , Willy Tarreau , Nicolas Ferre , Claudiu Beznea , Daniel Palmer , Alexandre Belloni Subject: [PATCH] Revert "macb: support the two tx descriptors on at91rm9200" Date: Wed, 9 Dec 2020 19:47:40 +0100 Message-Id: <20201209184740.16473-1-w@1wt.eu> X-Mailer: git-send-email 2.9.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This reverts commit 0a4e9ce17ba77847e5a9f87eed3c0ba46e3f82eb. The code was developed and tested on an MSC313E SoC, which seems to be half-way between the AT91RM9200 and the AT91SAM9260 in that it supports both the 2-descriptors mode and a Tx ring. It turns out that after the code was merged I could notice that the controller would sometimes lock up, and only when dealing with sustained bidirectional transfers, in which case it would report a Tx overrun condition right after having reported being ready, and will stop sending even after the status is cleared (a down/up cycle fixes it though). After adding lots of traces I couldn't spot a sequence pattern allowing to predict that this situation would happen. The chip comes with no documentation and other bits are often reported with no conclusive pattern either. It is possible that my change is wrong just like it is possible that the controller on the chip is bogus or at least unpredictable based on existing docs from other chips. I do not have an RM9200 at hand to test at the moment and a few tests run on a more recent 9G20 indicate that this code path cannot be used there to test the code on a 3rd platform. Since the MSC313E works fine in the single-descriptor mode, and that people using the old RM9200 very likely favor stability over performance, better revert this patch until we can test it on the original platform this part of the driver was written for. Note that the reverted patch was actually tested on MSC313E. Cc: Nicolas Ferre Cc: Claudiu Beznea Cc: Daniel Palmer Cc: Alexandre Belloni Link: https://lore.kernel.org/netdev/20201206092041.GA10646@1wt.eu/ Signed-off-by: Willy Tarreau --- drivers/net/ethernet/cadence/macb.h | 2 -- drivers/net/ethernet/cadence/macb_main.c | 46 ++++++-------------------------- 2 files changed, 8 insertions(+), 40 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h index 85be045..9fbdf53 100644 --- a/drivers/net/ethernet/cadence/macb.h +++ b/drivers/net/ethernet/cadence/macb.h @@ -1216,8 +1216,6 @@ struct macb { /* AT91RM9200 transmit queue (1 on wire + 1 queued) */ struct macb_tx_skb rm9200_txq[2]; - unsigned int rm9200_tx_tail; - unsigned int rm9200_tx_len; unsigned int max_tx_length; u64 ethtool_stats[GEM_STATS_LEN + QUEUE_STATS_LEN * MACB_MAX_QUEUES]; diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 817c7b0..352ae7f 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -3936,7 +3936,6 @@ static int at91ether_start(struct macb *lp) MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE) | MACB_BIT(TCOMP) | - MACB_BIT(RM9200_TBRE) | MACB_BIT(ISR_ROVR) | MACB_BIT(HRESP)); @@ -3953,7 +3952,6 @@ static void at91ether_stop(struct macb *lp) MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE) | MACB_BIT(TCOMP) | - MACB_BIT(RM9200_TBRE) | MACB_BIT(ISR_ROVR) | MACB_BIT(HRESP)); @@ -4023,10 +4021,11 @@ static netdev_tx_t at91ether_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct macb *lp = netdev_priv(dev); - unsigned long flags; - if (lp->rm9200_tx_len < 2) { - int desc = lp->rm9200_tx_tail; + if (macb_readl(lp, TSR) & MACB_BIT(RM9200_BNQ)) { + int desc = 0; + + netif_stop_queue(dev); /* Store packet information (to free when Tx completed) */ lp->rm9200_txq[desc].skb = skb; @@ -4040,15 +4039,6 @@ static netdev_tx_t at91ether_start_xmit(struct sk_buff *skb, return NETDEV_TX_OK; } - spin_lock_irqsave(&lp->lock, flags); - - lp->rm9200_tx_tail = (desc + 1) & 1; - lp->rm9200_tx_len++; - if (lp->rm9200_tx_len > 1) - netif_stop_queue(dev); - - spin_unlock_irqrestore(&lp->lock, flags); - /* Set address of the data in the Transmit Address register */ macb_writel(lp, TAR, lp->rm9200_txq[desc].mapping); /* Set length of the packet in the Transmit Control register */ @@ -4114,8 +4104,6 @@ static irqreturn_t at91ether_interrupt(int irq, void *dev_id) struct macb *lp = netdev_priv(dev); u32 intstatus, ctl; unsigned int desc; - unsigned int qlen; - u32 tsr; /* MAC Interrupt Status register indicates what interrupts are pending. * It is automatically cleared once read. @@ -4127,39 +4115,21 @@ static irqreturn_t at91ether_interrupt(int irq, void *dev_id) at91ether_rx(dev); /* Transmit complete */ - if (intstatus & (MACB_BIT(TCOMP) | MACB_BIT(RM9200_TBRE))) { + if (intstatus & MACB_BIT(TCOMP)) { /* The TCOM bit is set even if the transmission failed */ if (intstatus & (MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE))) dev->stats.tx_errors++; - spin_lock(&lp->lock); - - tsr = macb_readl(lp, TSR); - - /* we have three possibilities here: - * - all pending packets transmitted (TGO, implies BNQ) - * - only first packet transmitted (!TGO && BNQ) - * - two frames pending (!TGO && !BNQ) - * Note that TGO ("transmit go") is called "IDLE" on RM9200. - */ - qlen = (tsr & MACB_BIT(TGO)) ? 0 : - (tsr & MACB_BIT(RM9200_BNQ)) ? 1 : 2; - - while (lp->rm9200_tx_len > qlen) { - desc = (lp->rm9200_tx_tail - lp->rm9200_tx_len) & 1; + desc = 0; + if (lp->rm9200_txq[desc].skb) { dev_consume_skb_irq(lp->rm9200_txq[desc].skb); lp->rm9200_txq[desc].skb = NULL; dma_unmap_single(&lp->pdev->dev, lp->rm9200_txq[desc].mapping, lp->rm9200_txq[desc].size, DMA_TO_DEVICE); dev->stats.tx_packets++; dev->stats.tx_bytes += lp->rm9200_txq[desc].size; - lp->rm9200_tx_len--; } - - if (lp->rm9200_tx_len < 2 && netif_queue_stopped(dev)) - netif_wake_queue(dev); - - spin_unlock(&lp->lock); + netif_wake_queue(dev); } /* Work-around for EMAC Errata section 41.3.1 */