libata-sff: fix 32-bit PIO ATAPI regression

Commit 871af1210f13966ab911ed2166e4ab2ce775b99d (libata: Add 32bit
PIO support) has caused all kinds of errors on the ATAPI devices, so
it has been empirically proven that one shouldn't try to read/write
an extra data word when a device is not expecting it already. "Don't
do it then"; however, still use a chance to do 32-bit read/write one
last time when there are exactly 3 trailing bytes.

Oh, and stop pointlessly swapping the bytes to and fro on big-endian
machines by using io*_rep() accessors which shouldn't byte-swap.

This patch should fix the kernel.org bug #12609.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 0b299b0f81721bbe1446169b8fa5b51c86eecd2d..714cb046b594200a17d096768f0d8a45f89a835a 100644 (file)
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -773,18 +773,32 @@ unsigned int ata_sff_data_xfer32(struct ata_device *dev, unsigned char *buf,
        else
                iowrite32_rep(data_addr, buf, words);
 
+       /* Transfer trailing bytes, if any */
        if (unlikely(slop)) {
-               __le32 pad;
+               unsigned char pad[4];
+
+               /* Point buf to the tail of buffer */
+               buf += buflen - slop;
+
+               /*
+                * Use io*_rep() accessors here as well to avoid pointlessly
+                * swapping bytes to and fro on the big endian machines...
+                */
                if (rw == READ) {
-                       pad = cpu_to_le32(ioread32(ap->ioaddr.data_addr));
-                       memcpy(buf + buflen - slop, &pad, slop);
+                       if (slop < 3)
+                               ioread16_rep(data_addr, pad, 1);
+                       else
+                               ioread32_rep(data_addr, pad, 1);
+                       memcpy(buf, pad, slop);
                } else {
-                       memcpy(&pad, buf + buflen - slop, slop);
-                       iowrite32(le32_to_cpu(pad), ap->ioaddr.data_addr);
+                       memcpy(pad, buf, slop);
+                       if (slop < 3)
+                               iowrite16_rep(data_addr, pad, 1);
+                       else
+                               iowrite32_rep(data_addr, pad, 1);
                }
-               words++;
        }
-       return words << 2;
+       return (buflen + 1) & ~1;
 }
 EXPORT_SYMBOL_GPL(ata_sff_data_xfer32);