staging: comedi: addi_apci_3120: use dma_alloc_coherent()

Use `dma_alloc_coherent()` to allocate the DMA buffers instead of
using `__get_free_pages()` to allocate and `virt_to_bus()` to get the
hardware address.  The coherent buffers are fairly small - at most 4
pages (although there are two of them).  Use of `virt_to_bus()` is
discouraged.

Note: `struct addi_private` is used by some other ADDI-DATA drivers as
well, but this is the only one using the affected members.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/Kconfig

@@ -677,7 +677,7 @@ config COMEDI_ADDI_APCI_2200
 
 config COMEDI_ADDI_APCI_3120
 	tristate "ADDI-DATA APCI_3120/3001 support"
-	depends on VIRT_TO_BUS
+	depends on HAS_DMA
 	select COMEDI_FC
 	---help---
 	  Enable support for ADDI-DATA APCI_3120/3001 cards

drivers/staging/comedi/drivers/addi-data/addi_common.h

@@ -107,10 +107,9 @@ struct addi_private {
 	unsigned char b_DmaDoubleBuffer;	/*  we can use double buffering */
 	unsigned int ui_DmaActualBuffer;	/*  which buffer is used now */
 	unsigned short *ul_DmaBufferVirtual[2];	/*  pointers to DMA buffer */
-	unsigned int ul_DmaBufferHw[2];	/*  hw address of DMA buff */
+	dma_addr_t ul_DmaBufferHw[2];		/*  hw address of DMA buff */
 	unsigned int ui_DmaBufferSize[2];	/*  size of dma buffer in bytes */
 	unsigned int ui_DmaBufferUsesize[2];	/*  which size we may now used for transfer */
-	unsigned int ui_DmaBufferPageOrder[2];	/*  log2 of pages in buffer */
 	unsigned char b_DigitalOutputRegister;	/*  Digital Output Register */
 	unsigned char b_OutputMemoryStatus;
 	unsigned char b_TimerSelectMode;	/*  Contain data written at iobase + 0C */

drivers/staging/comedi/drivers/addi_apci_3120.c

@@ -95,17 +95,16 @@ static int apci3120_auto_attach(struct comedi_device *dev,
 	for (i = 0; i < 2; i++) {
 		for (order = 2; order >= 0; order--) {
 			devpriv->ul_DmaBufferVirtual[i] =
-			    (void *)__get_free_pages(GFP_KERNEL, order);
+			    dma_alloc_coherent(dev->hw_dev, PAGE_SIZE << order,
+					       &devpriv->ul_DmaBufferHw[i],
+					       GFP_KERNEL);
 
 			if (devpriv->ul_DmaBufferVirtual[i])
 				break;
 		}
 		if (!devpriv->ul_DmaBufferVirtual[i])
 			break;
-		devpriv->ui_DmaBufferPageOrder[i] = order;
 		devpriv->ui_DmaBufferSize[i] = PAGE_SIZE << order;
-		devpriv->ul_DmaBufferHw[i] =
-		    virt_to_bus(devpriv->ul_DmaBufferVirtual[i]);
 	}
 	if (!devpriv->ul_DmaBufferVirtual[0])
 		devpriv->us_UseDma = 0;
@@ -198,15 +197,16 @@ static void apci3120_detach(struct comedi_device *dev)
 		apci3120_reset(dev);
 	comedi_pci_detach(dev);
 	if (devpriv) {
-		if (devpriv->ul_DmaBufferVirtual[0]) {
-			free_pages((unsigned long)devpriv->
-				ul_DmaBufferVirtual[0],
-				devpriv->ui_DmaBufferPageOrder[0]);
-		}
-		if (devpriv->ul_DmaBufferVirtual[1]) {
-			free_pages((unsigned long)devpriv->
-				ul_DmaBufferVirtual[1],
-				devpriv->ui_DmaBufferPageOrder[1]);
+		unsigned int i;
+
+		for (i = 0; i < 2; i++) {
+			if (devpriv->ul_DmaBufferVirtual[i]) {
+				dma_free_coherent(dev->hw_dev,
+						  devpriv->ui_DmaBufferSize[i],
+						  devpriv->
+						  ul_DmaBufferVirtual[i],
+						  devpriv->ul_DmaBufferHw[i]);
+			}
 		}
 	}
 }