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

[Pekka Pietikainen <pp@xxxxxxxxxx>]

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;