The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 317a215d493230da361028ea8a4675de334bfa1a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024052505-confiding-stegosaur-016d@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 317a215d493230da361028ea8a4675de334bfa1a Mon Sep 17 00:00:00 2001 From: Ronald Wahl ronald.wahl@raritan.com Date: Mon, 13 May 2024 16:39:22 +0200 Subject: [PATCH] net: ks8851: Fix another TX stall caused by wrong ISR flag handling

Under some circumstances it may happen that the ks8851 Ethernet driver stops sending data.

Currently the interrupt handler resets the interrupt status flags in the hardware after handling TX. With this approach we may lose interrupts in the time window between handling the TX interrupt and resetting the TX interrupt status bit.

When all of the three following conditions are true then transmitting data stops:

- TX queue is stopped to wait for room in the hardware TX buffer - no queued SKBs in the driver (txq) that wait for being written to hw - hardware TX buffer is empty and the last TX interrupt was lost

This is because reenabling the TX queue happens when handling the TX interrupt status but if the TX status bit has already been cleared then this interrupt will never come.

With this commit the interrupt status flags will be cleared before they are handled. That way we stop losing interrupts.

The wrong handling of the ISR flags was there from the beginning but with commit 3dc5d4454545 ("net: ks8851: Fix TX stall caused by TX buffer overrun") the issue becomes apparent.

Fixes: 3dc5d4454545 ("net: ks8851: Fix TX stall caused by TX buffer overrun") Cc: "David S. Miller" davem@davemloft.net Cc: Eric Dumazet edumazet@google.com Cc: Jakub Kicinski kuba@kernel.org Cc: Paolo Abeni pabeni@redhat.com Cc: Simon Horman horms@kernel.org Cc: netdev@vger.kernel.org Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Ronald Wahl ronald.wahl@raritan.com Reviewed-by: Simon Horman horms@kernel.org Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/drivers/net/ethernet/micrel/ks8851_common.c b/drivers/net/ethernet/micrel/ks8851_common.c index 502518cdb461..6453c92f0fa7 100644 --- a/drivers/net/ethernet/micrel/ks8851_common.c +++ b/drivers/net/ethernet/micrel/ks8851_common.c @@ -328,7 +328,6 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) { struct ks8851_net *ks = _ks; struct sk_buff_head rxq; - unsigned handled = 0; unsigned long flags; unsigned int status; struct sk_buff *skb; @@ -336,24 +335,17 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) ks8851_lock(ks, &flags);

status = ks8851_rdreg16(ks, KS_ISR); + ks8851_wrreg16(ks, KS_ISR, status);

netif_dbg(ks, intr, ks->netdev, "%s: status 0x%04x\n", __func__, status);

- if (status & IRQ_LCI) - handled |= IRQ_LCI; - if (status & IRQ_LDI) { u16 pmecr = ks8851_rdreg16(ks, KS_PMECR); pmecr &= ~PMECR_WKEVT_MASK; ks8851_wrreg16(ks, KS_PMECR, pmecr | PMECR_WKEVT_LINK); - - handled |= IRQ_LDI; }

- if (status & IRQ_RXPSI) - handled |= IRQ_RXPSI; - if (status & IRQ_TXI) { unsigned short tx_space = ks8851_rdreg16(ks, KS_TXMIR);

@@ -365,20 +357,12 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) if (netif_queue_stopped(ks->netdev)) netif_wake_queue(ks->netdev); spin_unlock(&ks->statelock); - - handled |= IRQ_TXI; }

- if (status & IRQ_RXI) - handled |= IRQ_RXI; - if (status & IRQ_SPIBEI) { netdev_err(ks->netdev, "%s: spi bus error\n", __func__); - handled |= IRQ_SPIBEI; }

- ks8851_wrreg16(ks, KS_ISR, handled); - if (status & IRQ_RXI) { /* the datasheet says to disable the rx interrupt during * packet read-out, however we're masking the interrupt