>From 51908f611fb00195d98f1a552106c6d1709720c0 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Fri, 17 May 2013 18:20:46 -0400 Subject: [PATCH 2/2] drm/i915: Sync the scratch page after writting values to it. We don't sync the page after we have written to it - this is what you are suppose to when doing: pci_map_page .. write some values [ was missing a call to pci_dma_sync_single_for_device] .. read some values pci_unmap_page Signed-off-by: Konrad Rzeszutek Wilk --- drivers/char/agp/intel-gtt.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c index 701b328..89dd698 100644 --- a/drivers/char/agp/intel-gtt.c +++ b/drivers/char/agp/intel-gtt.c @@ -902,6 +902,9 @@ void intel_gtt_clear_range(unsigned int first_entry, unsigned int num_entries) intel_private.driver->write_entry(intel_private.base.scratch_page_dma, i, 0); } + pci_dma_sync_single_for_device(intel_private.pcidev, + intel_private.base.scratch_page_dma, + PAGE_SIZE, PCI_DMA_BIDIRECTIONAL); readl(intel_private.gtt+i-1); } EXPORT_SYMBOL(intel_gtt_clear_range); -- 1.8.1.2