[PATCH v2] mt76: mt7615: rework IRQ handling to prepare for MSI support

[PATCH v2] mt76: mt7615: rework IRQ handling to prepare for MSI support

[Felix Fietkau]

With MSI interrupts, IRQs must not be enabled from within the IRQ handler,
because that can lead to lost events.
Defer IRQ processing to a tasklet, which is also responsible for enabling
IRQs (to avoid race conditions against the handler)

Co-developed-by: Soul Huang <Soul.Huang@mediatek.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
v2: fix potential irq storm on init

 drivers/net/wireless/mediatek/mt76/mmio.c     |  3 +-
 .../net/wireless/mediatek/mt76/mt7615/init.c  |  2 ++
 .../net/wireless/mediatek/mt76/mt7615/mmio.c  | 29 ++++++++++++++-----
 .../wireless/mediatek/mt76/mt7615/mt7615.h    |  9 +++---
 4 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mmio.c b/drivers/net/wireless/mediatek/mt76/mmio.c
index 7ead6620bb8b..26353b6bce97 100644
--- a/drivers/net/wireless/mediatek/mt76/mmio.c
+++ b/drivers/net/wireless/mediatek/mt76/mmio.c
@@ -73,7 +73,8 @@ void mt76_set_irq_mask(struct mt76_dev *dev, u32 addr,
 	spin_lock_irqsave(&dev->mmio.irq_lock, flags);
 	dev->mmio.irqmask &= ~clear;
 	dev->mmio.irqmask |= set;
-	mt76_mmio_wr(dev, addr, dev->mmio.irqmask);
+	if (addr)
+		mt76_mmio_wr(dev, addr, dev->mmio.irqmask);
 	spin_unlock_irqrestore(&dev->mmio.irq_lock, flags);
 }
 EXPORT_SYMBOL_GPL(mt76_set_irq_mask);
diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/init.c b/drivers/net/wireless/mediatek/mt76/mt7615/init.c
index 96b7c6284833..cb626a2d9197 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/init.c
@@ -561,5 +561,7 @@ void mt7615_unregister_device(struct mt7615_dev *dev)
 	spin_unlock_bh(&dev->token_lock);
 	idr_destroy(&dev->token);
 
+	tasklet_disable(&dev->irq_tasklet);
+
 	mt76_free_device(&dev->mt76);
 }
diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mmio.c b/drivers/net/wireless/mediatek/mt76/mt7615/mmio.c
index 3849bb6b49d0..e9f9cda6bb59 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/mmio.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/mmio.c
@@ -80,30 +80,42 @@ mt7615_rx_poll_complete(struct mt76_dev *mdev, enum mt76_rxq_id q)
 static irqreturn_t mt7615_irq_handler(int irq, void *dev_instance)
 {
 	struct mt7615_dev *dev = dev_instance;
-	u32 intr;
 
-	intr = mt76_rr(dev, MT_INT_SOURCE_CSR);
-	mt76_wr(dev, MT_INT_SOURCE_CSR, intr);
+	mt76_wr(dev, MT_INT_MASK_CSR, 0);
 
 	if (!test_bit(MT76_STATE_INITIALIZED, &dev->mphy.state))
 		return IRQ_NONE;
 
-	trace_dev_irq(&dev->mt76, intr, dev->mt76.mmio.irqmask);
+	tasklet_schedule(&dev->irq_tasklet);
+
+	return IRQ_HANDLED;
+}
+
+static void mt7615_irq_tasklet(unsigned long data)
+{
+	struct mt7615_dev *dev = (struct mt7615_dev *)data;
+	u32 intr, mask = 0;
+
+	mt76_wr(dev, MT_INT_MASK_CSR, 0);
 
+	intr = mt76_rr(dev, MT_INT_SOURCE_CSR);
+	mt76_wr(dev, MT_INT_SOURCE_CSR, intr);
+
+	trace_dev_irq(&dev->mt76, intr, dev->mt76.mmio.irqmask);
 	intr &= dev->mt76.mmio.irqmask;
 
 	if (intr & MT_INT_TX_DONE_ALL) {
-		mt7615_irq_disable(dev, MT_INT_TX_DONE_ALL);
+		mask |= MT_INT_TX_DONE_ALL;
 		napi_schedule(&dev->mt76.tx_napi);
 	}
 
 	if (intr & MT_INT_RX_DONE(0)) {
-		mt7615_irq_disable(dev, MT_INT_RX_DONE(0));
+		mask |= MT_INT_RX_DONE(0);
 		napi_schedule(&dev->mt76.napi[0]);
 	}
 
 	if (intr & MT_INT_RX_DONE(1)) {
-		mt7615_irq_disable(dev, MT_INT_RX_DONE(1));
+		mask |= MT_INT_RX_DONE(1);
 		napi_schedule(&dev->mt76.napi[1]);
 	}
 
@@ -117,7 +129,7 @@ static irqreturn_t mt7615_irq_handler(int irq, void *dev_instance)
 		}
 	}
 
-	return IRQ_HANDLED;
+	mt76_set_irq_mask(&dev->mt76, MT_INT_MASK_CSR, mask, 0);
 }
 
 int mt7615_mmio_probe(struct device *pdev, void __iomem *mem_base,
@@ -154,6 +166,7 @@ int mt7615_mmio_probe(struct device *pdev, void __iomem *mem_base,
 
 	dev = container_of(mdev, struct mt7615_dev, mt76);
 	mt76_mmio_init(&dev->mt76, mem_base);
+	tasklet_init(&dev->irq_tasklet, mt7615_irq_tasklet, (unsigned long)dev);
 
 	dev->reg_map = map;
 	dev->ops = ops;
diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mt7615.h b/drivers/net/wireless/mediatek/mt76/mt7615/mt7615.h
index 4f0d29e5e595..10a98d38f77e 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/mt7615.h
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/mt7615.h
@@ -229,6 +229,8 @@ struct mt7615_dev {
 		struct mt76_phy mphy;
 	};
 
+	struct tasklet_struct irq_tasklet;
+
 	struct mt7615_phy phy;
 	u32 vif_mask;
 	u32 omac_mask;
@@ -404,12 +406,9 @@ static inline bool is_mt7663(struct mt76_dev *dev)
 
 static inline void mt7615_irq_enable(struct mt7615_dev *dev, u32 mask)
 {
-	mt76_set_irq_mask(&dev->mt76, MT_INT_MASK_CSR, 0, mask);
-}
+	mt76_set_irq_mask(&dev->mt76, 0, 0, mask);
 
-static inline void mt7615_irq_disable(struct mt7615_dev *dev, u32 mask)
-{
-	mt76_set_irq_mask(&dev->mt76, MT_INT_MASK_CSR, mask, 0);
+	tasklet_schedule(&dev->irq_tasklet);
 }
 
 static inline bool mt7615_firmware_offload(struct mt7615_dev *dev)
-- 
2.24.0

Re: [PATCH v2] mt76: mt7615: rework IRQ handling to prepare for MSI support

[Kalle Valo]

Felix Fietkau <nbd@nbd.name> writes:

> With MSI interrupts, IRQs must not be enabled from within the IRQ handler,
> because that can lead to lost events.
> Defer IRQ processing to a tasklet, which is also responsible for enabling
> IRQs (to avoid race conditions against the handler)
>
> Co-developed-by: Soul Huang <Soul.Huang@mediatek.com>
> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Soul's s-o-b is missing.

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches