async_tx: build-time toggling of async_{syndrome,xor}_val dma support

ioat3.2 does not support asynchronous error notifications which makes
the driver experience latencies when non-zero pq validate results are
expected.  Provide a mechanism for turning off async_xor_val and
async_syndrome_val via Kconfig.  This approach is generally useful for
any driver that specifies ASYNC_TX_DISABLE_CHANNEL_SWITCH and would like
to force the async_tx api to fall back to the synchronous path for
certain operations.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 252cf2d3f1da..189788f6351e 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -1206,6 +1206,16 @@ int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
                 device->timer_fn = ioat2_timer_event;
         }
 
+        #ifdef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
+        dma_cap_clear(DMA_PQ_VAL, dma->cap_mask);
+        dma->device_prep_dma_pq_val = NULL;
+        #endif
+
+        #ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
+        dma_cap_clear(DMA_XOR_VAL, dma->cap_mask);
+        dma->device_prep_dma_xor_val = NULL;
+        #endif
+
         /* -= IOAT ver.3 workarounds =- */
         /* Write CHANERRMSK_INT with 3E07h to mask out the errors
          * that can cause stability issues for IOAT ver.3