From: Benjamin Herrenschmidt Date: Wed, 13 Jul 2011 06:28:22 +0000 (+0000) Subject: drm/radeon: Do an MMIO read on interrupts when not uisng MSIs X-Git-Tag: firefly_0821_release~3680^2~4922^2~5 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f6a5693976fbc8e9fe4dde3040820082593c1757;p=firefly-linux-kernel-4.4.55.git drm/radeon: Do an MMIO read on interrupts when not uisng MSIs When not using MSIs, there is no guarantee that DMA from the device has been fully flushed to point where it's visible to the CPU when taking an interrupt. To get this guarantee, we need to perform an MMIO read from the device, which will flush all outstanding DMAs from bridges between the device and the system. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Dave Airlie --- diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c index 1741af86943c..f56e65579835 100644 --- a/drivers/gpu/drm/radeon/r600.c +++ b/drivers/gpu/drm/radeon/r600.c @@ -3302,6 +3302,10 @@ int r600_irq_process(struct radeon_device *rdev) if (!rdev->ih.enabled || rdev->shutdown) return IRQ_NONE; + /* No MSIs, need a dummy read to flush PCI DMAs */ + if (!rdev->msi_enabled) + RREG32(IH_RB_WPTR); + wptr = r600_get_ih_wptr(rdev); rptr = rdev->ih.rptr; DRM_DEBUG("r600_irq_process start: rptr %d, wptr %d\n", rptr, wptr);