Patch "PCI: mediatek: Clear interrupt status before dispatching handler" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    PCI: mediatek: Clear interrupt status before dispatching handler

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pci-mediatek-clear-interrupt-status-before-dispatchi.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 096fd4849adc3690fd0852c805dd38f1ad8f0002
Author: qizhong cheng <qizhong.cheng@xxxxxxxxxxxx>
Date:   Mon Dec 11 17:49:23 2023 +0800

    PCI: mediatek: Clear interrupt status before dispatching handler
    
    [ Upstream commit 4e11c29873a8a296a20f99b3e03095e65ebf897d ]
    
    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@xxxxxxxxxxxx
    Fixes: 43e6409db64d ("PCI: mediatek: Add MSI support for MT2712 and MT7622")
    Signed-off-by: qizhong cheng <qizhong.cheng@xxxxxxxxxxxx>
    Signed-off-by: Jianjun Wang <jianjun.wang@xxxxxxxxxxxx>
    Signed-off-by: Krzysztof Wilczyński <kwilczynski@xxxxxxxxxx>
    [bhelgaas: rewrap comment]
    Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
    Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
    Cc:  <stable@xxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 066e9e00de11..0d5be37660aa 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -605,14 +605,20 @@ 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 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) {
 					virq = irq_find_mapping(port->inner_domain, bit);
 					generic_handle_irq(virq);
 				}
 			}
-			/* Clear MSI interrupt status */
-			writel(MSI_STATUS, port->base + PCIE_INT_STATUS);
 		}
 	}