NTB: transport: Try harder to alloc an aligned MW buffer

Be a little wasteful if the (likely CMA) message window buffer is not
suitably aligned after our first attempt; allocate a buffer twice as big
as we need and manually align our MW buffer within it.

This was needed on Intel Broadwell DE platforms with intel_iommu=off
Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/ntb_transport.c

@@ -194,6 +194,8 @@ struct ntb_transport_mw {
 	void __iomem *vbase;
 	size_t xlat_size;
 	size_t buff_size;
+	size_t alloc_size;
+	void *alloc_addr;
 	void *virt_addr;
 	dma_addr_t dma_addr;
 };
@@ -672,13 +674,59 @@ static void ntb_free_mw(struct ntb_transport_ctx *nt, int num_mw)
 		return;
 
 	ntb_mw_clear_trans(nt->ndev, PIDX, num_mw);
-	dma_free_coherent(&pdev->dev, mw->buff_size,
-			  mw->virt_addr, mw->dma_addr);
+	dma_free_coherent(&pdev->dev, mw->alloc_size,
+			  mw->alloc_addr, mw->dma_addr);
 	mw->xlat_size = 0;
 	mw->buff_size = 0;
+	mw->alloc_size = 0;
+	mw->alloc_addr = NULL;
 	mw->virt_addr = NULL;
 }
 
+static int ntb_alloc_mw_buffer(struct ntb_transport_mw *mw,
+			       struct device *dma_dev, size_t align)
+{
+	dma_addr_t dma_addr;
+	void *alloc_addr, *virt_addr;
+	int rc;
+
+	alloc_addr = dma_alloc_coherent(dma_dev, mw->alloc_size,
+					&dma_addr, GFP_KERNEL);
+	if (!alloc_addr) {
+		dev_err(dma_dev, "Unable to alloc MW buff of size %zu\n",
+			mw->alloc_size);
+		return -ENOMEM;
+	}
+	virt_addr = alloc_addr;
+
+	/*
+	 * we must ensure that the memory address allocated is BAR size
+	 * aligned in order for the XLAT register to take the value. This
+	 * is a requirement of the hardware. It is recommended to setup CMA
+	 * for BAR sizes equal or greater than 4MB.
+	 */
+	if (!IS_ALIGNED(dma_addr, align)) {
+		if (mw->alloc_size > mw->buff_size) {
+			virt_addr = PTR_ALIGN(alloc_addr, align);
+			dma_addr = ALIGN(dma_addr, align);
+		} else {
+			rc = -ENOMEM;
+			goto err;
+		}
+	}
+
+	mw->alloc_addr = alloc_addr;
+	mw->virt_addr = virt_addr;
+	mw->dma_addr = dma_addr;
+
+	return 0;
+
+err:
+	dma_free_coherent(dma_dev, mw->alloc_size, alloc_addr, dma_addr);
+
+	return rc;
+}
+
 static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
 		      resource_size_t size)
 {
@@ -710,28 +758,20 @@ static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
 	/* Alloc memory for receiving data.  Must be aligned */
 	mw->xlat_size = xlat_size;
 	mw->buff_size = buff_size;
+	mw->alloc_size = buff_size;
 
-	mw->virt_addr = dma_alloc_coherent(&pdev->dev, buff_size,
-					   &mw->dma_addr, GFP_KERNEL);
-	if (!mw->virt_addr) {
+	rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
+	if (rc) {
+		mw->alloc_size *= 2;
+		rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
+		if (rc) {
+			dev_err(&pdev->dev,
+				"Unable to alloc aligned MW buff\n");
 			mw->xlat_size = 0;
 			mw->buff_size = 0;
-		dev_err(&pdev->dev, "Unable to alloc MW buff of size %zu\n",
-			buff_size);
-		return -ENOMEM;
+			mw->alloc_size = 0;
+			return rc;
 		}
-
-	/*
-	 * we must ensure that the memory address allocated is BAR size
-	 * aligned in order for the XLAT register to take the value. This
-	 * is a requirement of the hardware. It is recommended to setup CMA
-	 * for BAR sizes equal or greater than 4MB.
-	 */
-	if (!IS_ALIGNED(mw->dma_addr, xlat_align)) {
-		dev_err(&pdev->dev, "DMA memory %pad is not aligned\n",
-			&mw->dma_addr);
-		ntb_free_mw(nt, num_mw);
-		return -ENOMEM;
 	}
 
 	/* Notify HW the memory location of the receive buffer */