[PATCH v4] PCI: mediatek: Clear interrupt status before dispatching handler

[Jianjun Wang]

From: qizhong cheng <qizhong.cheng at mediatek.com>

We found a failure when used iperf tool for wifi performance testing,
there are some MSIs received while clearing the interrupt status,
these MSIs cannot be serviced.

The interrupt status can be cleared even the MSI status still remaining,
as an edge-triggered interrupts, its interrupt status should be cleared
before dispatching to the handler of device.

Fixes: 43e6409db64d ("PCI: mediatek: Add MSI support for MT2712 and MT7622")
Signed-off-by: qizhong cheng <qizhong.cheng at mediatek.com>
Signed-off-by: Jianjun Wang <jianjun.wang at mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Cc: stable at vger.kernel.org
---
v4:
 - Found that this patch has not been merged, resending it as v4.

v3:
 - Add Fix tag.

v2:
 - Update the subject line.
 - Improve the commit log and code comments.
---
 drivers/pci/controller/pcie-mediatek.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 66a8f73296fc..3fb7f08de061 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -617,12 +617,17 @@ static void mtk_pcie_intr_handler(struct irq_desc *desc)
 		if (status & MSI_STATUS){
 			unsigned long imsi_status;
 
+			/*
+			 * The interrupt status can be cleared even the MSI
+			 * status still remaining, hence as an edge-triggered
+			 * interrupts, its interrupt status should be cleared
+			 * before dispatching handler.
+			 */
+			writel(MSI_STATUS, port->base + PCIE_INT_STATUS);
 			while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
 				for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM)
 					generic_handle_domain_irq(port->inner_domain, bit);
 			}
-			/* Clear MSI interrupt status */
-			writel(MSI_STATUS, port->base + PCIE_INT_STATUS);
 		}
 	}
 
-- 
2.18.0