From: Damien Le Moal Date: Sat, 15 Apr 2023 02:35:41 +0000 (+0900) Subject: misc: pci_endpoint_test: Do not write status in IRQ handler X-Git-Tag: v6.6.17~4503^2~1^2~14 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=168e6f62e4298815125591ff9c85d374b2a93c6c;p=platform%2Fkernel%2Flinux-rpi.git misc: pci_endpoint_test: Do not write status in IRQ handler pci_endpoint_test_irqhandler() always rewrites the status register when an IRQ is raised, either as-is if STATUS_IRQ_RAISED is not set, or with STATUS_IRQ_RAISED cleared if that flag is set. The first case creates a race window with the endpoint side, meaning that the host side test driver may end up reading what it just wrote, thus losing the real status as set by the endpoint side before raising the next interrupt. This can prevent detecting that the STATUS_IRQ_RAISED flag was set by the endpoint. Remove this race window by not clearing the STATUS_IRQ_RAISED status flag and not rewriting that register for every IRQ received. Link: https://lore.kernel.org/r/20230415023542.77601-17-dlemoal@kernel.org Signed-off-by: Damien Le Moal Signed-off-by: Lorenzo Pieralisi Signed-off-by: Bjorn Helgaas Reviewed-by: Manivannan Sadhasivam --- diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c index 24efe3b..afd2577 100644 --- a/drivers/misc/pci_endpoint_test.c +++ b/drivers/misc/pci_endpoint_test.c @@ -159,10 +159,7 @@ static irqreturn_t pci_endpoint_test_irqhandler(int irq, void *dev_id) if (reg & STATUS_IRQ_RAISED) { test->last_irq = irq; complete(&test->irq_raised); - reg &= ~STATUS_IRQ_RAISED; } - pci_endpoint_test_writel(test, PCI_ENDPOINT_TEST_STATUS, - reg); return IRQ_HANDLED; }