From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D87083F6600; Tue, 17 Mar 2026 16:58:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773766688; cv=none; b=etcGLeZL1ecfKpWfjGhnsdlmUUskSAV91KV1ooXSMaI11sm1tn0Sa5OwfcLKF5Gc09KsxBi2bWs00vpYGdyNHxsvQ3+dw6Bp2wh8+NRkrY6PicxPncFe685KnH/FrPzylgA+IRnHAfetxLl780gBBnzkeU6w9WK5Vy4i6n43as4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773766688; c=relaxed/simple; bh=/JxGq33vblV3gtrs5b6xd7s4NLJy1MFHw5SNm3ub+bc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=J22FDTm9EiiRVaPVaD169BI7BbBXj6faqcWa1uNCmW8llbIotw8+gF5k4HW1EaGLHVn3HDyLoIZv3dYUKpyculhZeOj/tsO8AunnIL5nIxe3JQlAblzIfH5E56n5ahKwb7Q4Sqj8g4RkCGd7v7lHJTz4+KlNGCK+GfSgp6o1JGg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=l4s7aLjI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="l4s7aLjI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7AE55C2BC86; Tue, 17 Mar 2026 16:58:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1773766688; bh=/JxGq33vblV3gtrs5b6xd7s4NLJy1MFHw5SNm3ub+bc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=l4s7aLjIJrFa3WLUtH5rTs2mINq/9QSVsSdBxk4p2iU6GMuwiJ2bsrylpE0IEyWJo tMYELSk9N6PD29XDVGj/NVvSf8ASyuJQeAPkZb9NK5KhC3N3fA/whXBEsLSotJmmFl fgN1/HS4UiFqBuD45gOYJl8UNn7LMzvGvIG9KdqM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Quanyang Wang , Kevin Hao , Simon Horman , Jakub Kicinski Subject: [PATCH 6.19 299/378] net: macb: Shuffle the tx ring before enabling tx Date: Tue, 17 Mar 2026 17:34:16 +0100 Message-ID: <20260317163018.007193555@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260317163006.959177102@linuxfoundation.org> References: <20260317163006.959177102@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kevin Hao commit 881a0263d502e1a93ebc13a78254e9ad19520232 upstream. Quanyang observed that when using an NFS rootfs on an AMD ZynqMp board, the rootfs may take an extended time to recover after a suspend. Upon investigation, it was determined that the issue originates from a problem in the macb driver. According to the Zynq UltraScale TRM [1], when transmit is disabled, the transmit buffer queue pointer resets to point to the address specified by the transmit buffer queue base address register. In the current implementation, the code merely resets `queue->tx_head` and `queue->tx_tail` to '0'. This approach presents several issues: - Packets already queued in the tx ring are silently lost, leading to memory leaks since the associated skbs cannot be released. - Concurrent write access to `queue->tx_head` and `queue->tx_tail` may occur from `macb_tx_poll()` or `macb_start_xmit()` when these values are reset to '0'. - The transmission may become stuck on a packet that has already been sent out, with its 'TX_USED' bit set, but has not yet been processed. However, due to the manipulation of 'queue->tx_head' and 'queue->tx_tail', `macb_tx_poll()` incorrectly assumes there are no packets to handle because `queue->tx_head == queue->tx_tail`. This issue is only resolved when a new packet is placed at this position. This is the root cause of the prolonged recovery time observed for the NFS root filesystem. To resolve this issue, shuffle the tx ring and tx skb array so that the first unsent packet is positioned at the start of the tx ring. Additionally, ensure that updates to `queue->tx_head` and `queue->tx_tail` are properly protected with the appropriate lock. [1] https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm Fixes: bf9cf80cab81 ("net: macb: Fix tx/rx malfunction after phy link down and up") Reported-by: Quanyang Wang Signed-off-by: Kevin Hao Cc: stable@vger.kernel.org Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260307-zynqmp-v2-1-6ef98a70e1d0@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/cadence/macb_main.c | 98 ++++++++++++++++++++++++++++++- 1 file changed, 95 insertions(+), 3 deletions(-) --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include "macb.h" @@ -668,6 +669,97 @@ static void macb_mac_link_down(struct ph netif_tx_stop_all_queues(ndev); } +/* Use juggling algorithm to left rotate tx ring and tx skb array */ +static void gem_shuffle_tx_one_ring(struct macb_queue *queue) +{ + unsigned int head, tail, count, ring_size, desc_size; + struct macb_tx_skb tx_skb, *skb_curr, *skb_next; + struct macb_dma_desc *desc_curr, *desc_next; + unsigned int i, cycles, shift, curr, next; + struct macb *bp = queue->bp; + unsigned char desc[24]; + unsigned long flags; + + desc_size = macb_dma_desc_get_size(bp); + + if (WARN_ON_ONCE(desc_size > ARRAY_SIZE(desc))) + return; + + spin_lock_irqsave(&queue->tx_ptr_lock, flags); + head = queue->tx_head; + tail = queue->tx_tail; + ring_size = bp->tx_ring_size; + count = CIRC_CNT(head, tail, ring_size); + + if (!(tail % ring_size)) + goto unlock; + + if (!count) { + queue->tx_head = 0; + queue->tx_tail = 0; + goto unlock; + } + + shift = tail % ring_size; + cycles = gcd(ring_size, shift); + + for (i = 0; i < cycles; i++) { + memcpy(&desc, macb_tx_desc(queue, i), desc_size); + memcpy(&tx_skb, macb_tx_skb(queue, i), + sizeof(struct macb_tx_skb)); + + curr = i; + next = (curr + shift) % ring_size; + + while (next != i) { + desc_curr = macb_tx_desc(queue, curr); + desc_next = macb_tx_desc(queue, next); + + memcpy(desc_curr, desc_next, desc_size); + + if (next == ring_size - 1) + desc_curr->ctrl &= ~MACB_BIT(TX_WRAP); + if (curr == ring_size - 1) + desc_curr->ctrl |= MACB_BIT(TX_WRAP); + + skb_curr = macb_tx_skb(queue, curr); + skb_next = macb_tx_skb(queue, next); + memcpy(skb_curr, skb_next, sizeof(struct macb_tx_skb)); + + curr = next; + next = (curr + shift) % ring_size; + } + + desc_curr = macb_tx_desc(queue, curr); + memcpy(desc_curr, &desc, desc_size); + if (i == ring_size - 1) + desc_curr->ctrl &= ~MACB_BIT(TX_WRAP); + if (curr == ring_size - 1) + desc_curr->ctrl |= MACB_BIT(TX_WRAP); + memcpy(macb_tx_skb(queue, curr), &tx_skb, + sizeof(struct macb_tx_skb)); + } + + queue->tx_head = count; + queue->tx_tail = 0; + + /* Make descriptor updates visible to hardware */ + wmb(); + +unlock: + spin_unlock_irqrestore(&queue->tx_ptr_lock, flags); +} + +/* Rotate the queue so that the tail is at index 0 */ +static void gem_shuffle_tx_rings(struct macb *bp) +{ + struct macb_queue *queue; + int q; + + for (q = 0, queue = bp->queues; q < bp->num_queues; q++, queue++) + gem_shuffle_tx_one_ring(queue); +} + static void macb_mac_link_up(struct phylink_config *config, struct phy_device *phy, unsigned int mode, phy_interface_t interface, @@ -706,8 +798,6 @@ static void macb_mac_link_up(struct phyl ctrl |= MACB_BIT(PAE); for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { - queue->tx_head = 0; - queue->tx_tail = 0; queue_writel(queue, IER, bp->rx_intr_mask | MACB_TX_INT_FLAGS | MACB_BIT(HRESP)); } @@ -721,8 +811,10 @@ static void macb_mac_link_up(struct phyl spin_unlock_irqrestore(&bp->lock, flags); - if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC)) + if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC)) { macb_set_tx_clk(bp, speed); + gem_shuffle_tx_rings(bp); + } /* Enable Rx and Tx; Enable PTP unicast */ ctrl = macb_readl(bp, NCR);