releases/6.1.75/pci-mediatek-clear-interrupt-status-before-dispatching-handler.patch

From 4e11c29873a8a296a20f99b3e03095e65ebf897d Mon Sep 17 00:00:00 2001
From: qizhong cheng <qizhong.cheng@mediatek.com>
Date: Mon, 11 Dec 2023 17:49:23 +0800
Subject: PCI: mediatek: Clear interrupt status before dispatching handler
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From: qizhong cheng <qizhong.cheng@mediatek.com>

commit 4e11c29873a8a296a20f99b3e03095e65ebf897d upstream.

We found a failure when using the iperf tool during WiFi performance
testing, where some MSIs were received while clearing the interrupt
status, and these MSIs cannot be serviced.

The interrupt status can be cleared even if the MSI status remains pending.
As such, given the edge-triggered interrupt type, its status should be
cleared before being dispatched to the handler of the underling device.

[kwilczynski: commit log, code comment wording]
Link: https://lore.kernel.org/linux-pci/20231211094923.31967-1-jianjun.wang@mediatek.com
Fixes: 43e6409db64d ("PCI: mediatek: Add MSI support for MT2712 and MT7622")
Signed-off-by: qizhong cheng <qizhong.cheng@mediatek.com>
Signed-off-by: Jianjun Wang <jianjun.wang@mediatek.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: rewrap comment]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc:  <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/pci/controller/pcie-mediatek.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -617,12 +617,18 @@ static void mtk_pcie_intr_handler(struct
 		if (status & MSI_STATUS){
 			unsigned long imsi_status;
 
+			/*
+			 * The interrupt status can be cleared even if the
+			 * MSI status remains pending. As such, given the
+			 * edge-triggered interrupt type, its status should
+			 * be cleared before being dispatched to the
+			 * handler of the underlying device.
+			 */
+			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);
 		}
 	}