[PATCH net-next v3 03/12] net: ethernet: cortina: Drain free queue IRQ before resize

[Linus Walleij <linusw@kernel.org>]

The software free queue interrupt remains registered while both netdevs
are down. Merely masking the device source does not stop a threaded
handler which was already woken. That handler can refill the queue while
resize frees its ring and page metadata, or re-enable the source after
teardown.

The free queue interrupt is routed through port 1. Disable that Linux IRQ
for the entire resize. disable_irq() drains hard and threaded handlers and
prevents a new thread from being woken.

After the drain, mask the device source and rebuild the queue. If setup
succeeds, re-enable the source before the Linux IRQ. On failure, keep the
source masked, clear freed queue state and restore the Linux IRQ so a later
open retries setup safely.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 40 +++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 15ad9f721dd5..a2daf22e7698 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -984,6 +984,8 @@ static int geth_setup_freeq(struct gemini_ethernet *geth)
 	}
 
 	kfree(geth->freeq_pages);
+	geth->freeq_pages = NULL;
+	geth->num_freeq_pages = 0;
 err_freeq:
 	dma_free_coherent(geth->dev,
 			  sizeof(*geth->freeq_ring) << geth->freeq_order,
@@ -1024,10 +1026,28 @@ static void geth_cleanup_freeq(struct gemini_ethernet *geth)
 	}
 
 	kfree(geth->freeq_pages);
+	geth->freeq_pages = NULL;
+	geth->num_freeq_pages = 0;
 
 	dma_free_coherent(geth->dev,
 			  sizeof(*geth->freeq_ring) << geth->freeq_order,
 			  geth->freeq_ring, geth->freeq_dma_base);
+	geth->freeq_ring = NULL;
+}
+
+static void geth_set_freeq_irq(struct gemini_ethernet *geth, bool enable)
+{
+	unsigned long flags;
+	u32 val;
+
+	spin_lock_irqsave(&geth->irq_lock, flags);
+	val = readl(geth->base + GLOBAL_INTERRUPT_ENABLE_4_REG);
+	if (enable)
+		val |= SWFQ_EMPTY_INT_BIT;
+	else
+		val &= ~SWFQ_EMPTY_INT_BIT;
+	writel(val, geth->base + GLOBAL_INTERRUPT_ENABLE_4_REG);
+	spin_unlock_irqrestore(&geth->irq_lock, flags);
 }
 
 /**
@@ -1047,8 +1067,6 @@ static int geth_resize_freeq(struct gemini_ethernet_port *port)
 	struct net_device *other_netdev;
 	unsigned int new_size = 0;
 	unsigned int new_order;
-	unsigned long flags;
-	u32 en;
 	int ret;
 
 	/* The software free queue interrupt is routed through port 1. */
@@ -1080,16 +1098,11 @@ static int geth_resize_freeq(struct gemini_ethernet_port *port)
 	new_order = min(15, ilog2(new_size - 1) + 1);
 	dev_dbg(geth->dev, "set shared queue to size %d order %d\n",
 		new_size, new_order);
-	if (geth->freeq_order == new_order)
+	if (geth->freeq_ring && geth->freeq_order == new_order)
 		return 0;
 
-	spin_lock_irqsave(&geth->irq_lock, flags);
-
-	/* Disable the software queue IRQs */
-	en = readl(geth->base + GLOBAL_INTERRUPT_ENABLE_4_REG);
-	en &= ~SWFQ_EMPTY_INT_BIT;
-	writel(en, geth->base + GLOBAL_INTERRUPT_ENABLE_4_REG);
-	spin_unlock_irqrestore(&geth->irq_lock, flags);
+	disable_irq(geth->port1->irq);
+	geth_set_freeq_irq(geth, false);
 
 	/* Drop the old queue */
 	if (geth->freeq_ring)
@@ -1103,10 +1116,9 @@ static int geth_resize_freeq(struct gemini_ethernet_port *port)
 	 * after probe(), this is where the interrupts get turned on
 	 * in the first place.
 	 */
-	spin_lock_irqsave(&geth->irq_lock, flags);
-	en |= SWFQ_EMPTY_INT_BIT;
-	writel(en, geth->base + GLOBAL_INTERRUPT_ENABLE_4_REG);
-	spin_unlock_irqrestore(&geth->irq_lock, flags);
+	if (!ret)
+		geth_set_freeq_irq(geth, true);
+	enable_irq(geth->port1->irq);
 
 	return ret;
 }

-- 
2.55.0