[PATCH mt76-next 7/9] wifi: mt76: mt7996: fix RX buffer size of MCU event

[Shayne Chen]

Some management frames are first processed by the firmware and then
passed to the driver through the MCU event rings. In CONNAC3, event rings
do not support scatter-gather and have a size limitation of 2048 bytes.
If a packet sized between 1728 and 2048 bytes arrives from an event ring,
the ring will hang because the driver attempts to use scatter-gather to
process it.

To fix this, include the size of struct skb_shared_info in the MCU RX
buffer size to prevent scatter-gather from being used for event skb in
mt76_dma_rx_fill_buf().

Fixes: 98686cd21624 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Co-developed-by: Peter Chiu <chui-hao.chiu at mediatek.com>
Signed-off-by: Peter Chiu <chui-hao.chiu at mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen at mediatek.com>
---
 drivers/net/wireless/mediatek/mt76/mt7996/dma.c    | 4 ++--
 drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/dma.c b/drivers/net/wireless/mediatek/mt76/mt7996/dma.c
index fe8cc1d3f738..c8bef0b2a144 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/dma.c
@@ -531,7 +531,7 @@ int mt7996_dma_init(struct mt7996_dev *dev)
 	ret = mt76_queue_alloc(dev, &dev->mt76.q_rx[MT_RXQ_MCU],
 			       MT_RXQ_ID(MT_RXQ_MCU),
 			       MT7996_RX_MCU_RING_SIZE,
-			       MT_RX_BUF_SIZE,
+			       MT7996_RX_MCU_BUF_SIZE,
 			       MT_RXQ_RING_BASE(MT_RXQ_MCU));
 	if (ret)
 		return ret;
@@ -540,7 +540,7 @@ int mt7996_dma_init(struct mt7996_dev *dev)
 	ret = mt76_queue_alloc(dev, &dev->mt76.q_rx[MT_RXQ_MCU_WA],
 			       MT_RXQ_ID(MT_RXQ_MCU_WA),
 			       MT7996_RX_MCU_RING_SIZE_WA,
-			       MT_RX_BUF_SIZE,
+			       MT7996_RX_MCU_BUF_SIZE,
 			       MT_RXQ_RING_BASE(MT_RXQ_MCU_WA));
 	if (ret)
 		return ret;
diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h b/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
index c75189a02316..1ad6bc046f7c 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
@@ -29,6 +29,9 @@
 #define MT7996_RX_RING_SIZE		1536
 #define MT7996_RX_MCU_RING_SIZE		512
 #define MT7996_RX_MCU_RING_SIZE_WA	1024
+/* scatter-gather of mcu event is not supported in connac3 */
+#define MT7996_RX_MCU_BUF_SIZE		(2048 + \
+					 SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
 
 #define MT7996_DEVICE_ID		0x7990
 #define MT7996_DEVICE_ID_2		0x7991
-- 
2.39.2