Dealing with buggy hardware (was: b44 and 4g4g)

[Pekka Pietikainen]

On Mon, May 31, 2004 at 11:21:04PM +0300, Pekka Pietikainen wrote:
> After diagnosing 
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=118165
> for a while
> 
> it seems that bcm4401 is quite broken when DMA:ing from/to
> addresses that are > 1GB. This only is a problem with > 1GB of physical
> memory and when using a 4:4 split.
And here's a workaround-everything-in-the-driver version that makes 
everything work. Cc:d to linux-kernel to get wider coverage.

There _really_ has to be a better way of dealing with hardware problems like
this (with a 512 entry TX ring this uses almost 800k of GFP_DMA, probably
should be made smaller in any case...):

(And again, please prepare your barf-bags!)

--- ../b44.c	2004-06-05 22:54:50.210817784 +0300
+++ b44.c	2004-06-05 22:54:56.721827960 +0300
@@ -67,6 +67,7 @@
 #define NEXT_TX(N)		(((N) + 1) & (B44_TX_RING_SIZE - 1))
 
 #define RX_PKT_BUF_SZ		(1536 + bp->rx_offset + 64)
+#define TX_PKT_BUF_SZ		(B44_MAX_MTU + ETH_HLEN + 8)
 
 /* minimum number of free TX descriptors required to wake up TX process */
 #define B44_TX_WAKEUP_THRESH		(B44_TX_RING_SIZE / 4)
@@ -82,6 +83,12 @@
 
 static int b44_debug = -1;	/* -1 == use B44_DEF_MSG_ENABLE as value */
 
+/* Hardware bug work-around, the chip seems to be unable to do PCI DMA
+   to anything above 1GB :-( */
+
+#define B44_DMA_MASK 0x3fffffff
+static int b44_use_bounce_buffers = 0;
+
 static struct pci_device_id b44_pci_tbl[] = {
 	{ PCI_VENDOR_ID_BROADCOM, PCI_DEVICE_ID_BCM4401,
 	  PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0UL },
@@ -634,7 +641,13 @@
 		src_map = &bp->rx_buffers[src_idx];
 	dest_idx = dest_idx_unmasked & (B44_RX_RING_SIZE - 1);
 	map = &bp->rx_buffers[dest_idx];
-	skb = dev_alloc_skb(RX_PKT_BUF_SZ);
+
+	if(!b44_use_bounce_buffers) {
+		skb = dev_alloc_skb(RX_PKT_BUF_SZ);
+	} else {
+		/* Sigh... */
+		skb = __dev_alloc_skb(RX_PKT_BUF_SZ,GFP_DMA);
+	}
 	if (skb == NULL)
 		return -ENOMEM;
 
@@ -918,6 +931,10 @@
 	}
 
 	entry = bp->tx_prod;
+	if(virt_to_bus(skb->data) + skb->len > B44_PCI_DMA_MAX) {
+		memcpy(bp->tx_bufs+entry*TX_PKT_BUF_SZ,skb->data,skb->len);
+		skb->data=bp->tx_bufs+entry*TX_PKT_BUF_SZ;
+	}
 	mapping = pci_map_single(bp->pdev, skb->data, len, PCI_DMA_TODEVICE);
 
 	bp->tx_buffers[entry].skb = skb;
@@ -1066,6 +1083,11 @@
 				    bp->tx_ring, bp->tx_ring_dma);
 		bp->tx_ring = NULL;
 	}
+	if (bp->tx_bufs) {
+		pci_free_consistent(bp->pdev, B44_TX_RING_SIZE * TX_PKT_BUF_SZ,
+				    bp->tx_bufs, bp->tx_bufs_dma);
+		bp->tx_bufs = NULL;
+	}
 }
 
 /*
@@ -1088,6 +1110,13 @@
 		goto out_err;
 	memset(bp->tx_buffers, 0, size);
 
+	if(b44_use_bounce_buffers) {
+		size = B44_TX_RING_SIZE * TX_PKT_BUF_SZ;
+		bp->tx_bufs = pci_alloc_consistent(bp->pdev, size, &bp->tx_bufs_dma);
+		if (!bp->tx_bufs)
+			goto out_err;
+		memset(bp->tx_bufs, 0, size);
+	}
 	size = DMA_TABLE_BYTES;
 	bp->rx_ring = pci_alloc_consistent(bp->pdev, size, &bp->rx_ring_dma);
 	if (!bp->rx_ring)
@@ -1724,12 +1753,25 @@
 
 	pci_set_master(pdev);
 
-	err = pci_set_dma_mask(pdev, (u64) 0xffffffff);
+#ifdef CONFIG_X86_4G
+	/* XXX only set if > 1GB of physmem */
+	b44_use_bounce_buffers=1;
+#endif
+	err = pci_set_dma_mask(pdev, (u64) B44_DMA_MASK);
 	if (err) {
 		printk(KERN_ERR PFX "No usable DMA configuration, "
 		       "aborting.\n");
 		goto err_out_free_res;
 	}
+	
+	if(b44_use_bounce_buffers) {
+		err = pci_set_consistent_dma_mask(pdev, (u64) B44_DMA_MASK);
+		if (err) {
+			printk(KERN_ERR PFX "No usable DMA configuration, "
+			       "aborting.\n");
+			goto err_out_free_res;
+		}
+	}
 
 	b44reg_base = pci_resource_start(pdev, 0);
 	b44reg_len = pci_resource_len(pdev, 0);
--- ../b44.h	2004-06-04 20:03:16.000000000 +0300
+++ b44.h	2004-06-05 21:45:19.000000000 +0300
@@ -503,6 +503,7 @@
 
 	struct ring_info	*rx_buffers;
 	struct ring_info	*tx_buffers;
+	unsigned char		*tx_bufs; 
 
 	u32			dma_offset;
 	u32			flags;
@@ -534,7 +535,7 @@
 	struct pci_dev		*pdev;
 	struct net_device	*dev;
 
-	dma_addr_t		rx_ring_dma, tx_ring_dma;
+	dma_addr_t		rx_ring_dma, tx_ring_dma,tx_bufs_dma;
 
 	u32			rx_pending;
 	u32			tx_pending;

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