ioat3: dca and raid operations are incompatible

RAID operations cause a system hang on platforms with DCA
(Direct-Cache-Access) enabled.  So turn off RAID capabilities in this
case.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 9 insertions, 1 deletions

diff --git a/drivers/dma/ioat/dca.c b/drivers/dma/ioat/dca.c
index 14f0a782df44..abd9038e06b1 100644
--- a/drivers/dma/ioat/dca.c
+++ b/drivers/dma/ioat/dca.c
@@ -103,7 +103,7 @@ static int dca_enabled_in_bios(struct pci_dev *pdev)
         return res;
 }
 
-static int system_has_dca_enabled(struct pci_dev *pdev)
+int system_has_dca_enabled(struct pci_dev *pdev)
 {
         if (boot_cpu_has(X86_FEATURE_DCA))
                 return dca_enabled_in_bios(pdev);
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 35d1e33afd5b..4f305f61f878 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -1117,6 +1117,7 @@ static int __devinit ioat3_dma_self_test(struct ioatdma_device *device)
 int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
 {
         struct pci_dev *pdev = device->pdev;
+        int dca_en = system_has_dca_enabled(pdev);
         struct dma_device *dma;
         struct dma_chan *c;
         struct ioat_chan_common *chan;
@@ -1137,6 +1138,11 @@ int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
         dma->device_prep_dma_interrupt = ioat3_prep_interrupt_lock;
 
         cap = readl(device->reg_base + IOAT_DMA_CAP_OFFSET);
+
+        /* dca is incompatible with raid operations */
+        if (dca_en && (cap & (IOAT_CAP_XOR|IOAT_CAP_PQ)))
+                cap &= ~(IOAT_CAP_XOR|IOAT_CAP_PQ);
+
         if (cap & IOAT_CAP_XOR) {
                 is_raid_device = true;
                 dma->max_xor = 8;
diff --git a/drivers/dma/ioat/hw.h b/drivers/dma/ioat/hw.h
index 99afb12bd409..60e675455b6a 100644
--- a/drivers/dma/ioat/hw.h
+++ b/drivers/dma/ioat/hw.h
@@ -39,6 +39,8 @@
 #define IOAT_VER_3_0            0x30    /* Version 3.0 */
 #define IOAT_VER_3_2            0x32    /* Version 3.2 */
 
+int system_has_dca_enabled(struct pci_dev *pdev);
+
 struct ioat_dma_descriptor {
         uint32_t        size;
         union {