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SubjectRe: [PATCH] PCI: Mediatek: clear irq status after irq dispathed to avoid reentry
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On Wed, 2017-12-20 at 10:52 +0800, honghui.zhang@mediatek.com wrote:
> From: Honghui Zhang <honghui.zhang@mediatek.com>
>
> There maybe a same irq reentry scenario after irq received in current
> irq handle flow:
> EP device PCIe host driver EP driver
> 1. issue an irq
> 2. received irq
> 3. clear irq status
> 4. dispatch irq
> 5. clear irq source
> The irq status was not successfully cleared at step 2 since the irq
> source was not cleared yet. So the PCIe host driver may receive the
> same irq after step 5. Then there's an irq reentry occurred.
> Even worse, if the reentry irq was not an irq that EP driver expected,
> it may not handle the irq. Then we may run into the dead loop from
> step 2 to step 4.
> Clear the irq status after irq have been dispatched to avoid the irq
> reentry.
>
> Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
> ---
> drivers/pci/host/pcie-mediatek.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
> index db93efd..3248771 100644
> --- a/drivers/pci/host/pcie-mediatek.c
> +++ b/drivers/pci/host/pcie-mediatek.c
> @@ -605,11 +605,11 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>
> while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) {
> for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) {
> - /* Clear the INTx */
> - writel(1 << bit, port->base + PCIE_INT_STATUS);
> virq = irq_find_mapping(port->irq_domain,
> bit - INTX_SHIFT);
> generic_handle_irq(virq);
> + /* Clear the INTx */
> + writel(1 << bit, port->base + PCIE_INT_STATUS);
> }
> }
>
> @@ -619,10 +619,10 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>
> while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
> for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) {
> - /* Clear the MSI */
> - writel(1 << bit, port->base + PCIE_IMSI_STATUS);
> virq = irq_find_mapping(port->msi_domain, bit);
> generic_handle_irq(virq);
> + /* Clear the MSI */
> + writel(1 << bit, port->base + PCIE_IMSI_STATUS);
> }
> }
> /* Clear MSI interrupt status */

Acked-by: Ryder Lee <ryder.lee@mediatek.com>

Thanks.


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