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SubjectRe: [PATCH] USB/ISP1760: Fix for unaligned exceptions
Bryan Wu wrote:
> From: Michael Hennerich <michael.hennerich@analog.com>
> Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> Signed-off-by: Bryan Wu <cooloney@kernel.org>
> ---
> drivers/usb/host/isp1760-hcd.c | 67 ++++++++++++++++++++++++++++-----------
> 1 files changed, 48 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c
> index 8017f1c..00bece2 100644
> --- a/drivers/usb/host/isp1760-hcd.c
> +++ b/drivers/usb/host/isp1760-hcd.c
> @@ -136,12 +136,21 @@ static void priv_read_copy(struct isp1760_hcd *priv, u32 *src,
> return;
> }
>
> - while (len >= 4) {
> - *src = __raw_readl(dst);
> - len -= 4;
> - src++;
> - dst++;
> - }
> + if (unlikely((u32)src & 0x3)) {
> + while (len >= 4) {
> + put_unaligned(__raw_readl(dst), src);
> + len -= 4;
> + src++;
> + dst++;
> + }
> + } else {
> + while (len >= 4) {
> + *src = __raw_readl(dst);
> + len -= 4;
> + src++;
> + dst++;
> + }
> + }
>
> if (!len)
> return;
> @@ -159,25 +168,45 @@ static void priv_read_copy(struct isp1760_hcd *priv, u32 *src,
> len--;
> buff8++;
> }
> +
> }
>
> static void priv_write_copy(const struct isp1760_hcd *priv, const u32 *src,
> __u32 __iomem *dst, u32 len)
> {
> - while (len >= 4) {
> - __raw_writel(*src, dst);
> - len -= 4;
> - src++;
> - dst++;
> - }
>
> - if (!len)
> - return;
> - /* in case we have 3, 2 or 1 by left. The buffer is allocated and the
> - * extra bytes should not be read by the HW
> - */
> -
> - __raw_writel(*src, dst);
The link [1] you sent me reports an unaligned access which occurred here.
So I thing the access to *src should be either a get_unaligned helper or a
byte read loop like I did it in the read path.
The r8a66597 is doing the same thing (as you suggest) for one SH machine.
However, I'm not convinced to fix it that way: The buffer should be
properly aligned by the driver. Unless there is HW which requires
unaligned data, I would prefer just to fix this unaligned access.
According to the thread in [1] a similar patch fixed it for the user until
he dropped into another bug.

> + if (unlikely((u32)src & 0x3)) {
> + while (len >= 4) {
> + __raw_writel(get_unaligned(src), dst);
> + len -= 4;
> + src++;
> + dst++;
> + }
> +
> + if (!len)
> + return;
> + /* in case we have 3, 2 or 1 by left. The buffer is allocated and the
> + * extra bytes should not be read by the HW
> + */
> +
> + __raw_writel(get_unaligned(src), dst);
> +
> + } else{
> + while (len >= 4) {
> + __raw_writel(*src, dst);
> + len -= 4;
> + src++;
> + dst++;
> + }
> +
> + if (!len)
> + return;
> + /* in case we have 3, 2 or 1 by left. The buffer is allocated and the
> + * extra bytes should not be read by the HW
> + */
> +
> + __raw_writel(*src, dst);
> + }
> }
>
> /* memory management of the 60kb on the chip from 0x1000 to 0xffff */

[1]
http://blackfin.uclinux.org/gf/project/uclinux-dist/forum/?action=ForumBrowse&_forum_action=MessageReply&message_id=64889

Sebastian


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