95 lines
3.1 KiB
Diff
95 lines
3.1 KiB
Diff
From: Stanislaw Gruszka <sgruszka@redhat.com>
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Date: Sun, 2 Nov 2014 13:38:47 +0100
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Subject: [PATCH] rt2x00: do not align payload on modern H/W
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RT2800 and newer hardware require padding between header and payload if
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header length is not multiple of 4.
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For historical reasons we also align payload to to 4 bytes boundary, but
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such alignment is not needed on modern H/W.
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Patch improve performance on embedded CPUs and _possibly_ fixes
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skb_under_panic problems reported from time to time:
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https://bugzilla.kernel.org/show_bug.cgi?id=84911
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https://bugzilla.kernel.org/show_bug.cgi?id=72471
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http://marc.info/?l=linux-wireless&m=139108549530402&w=2
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https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1087591
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But we can not explain or otherwise confirm the patch fixes this panic
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issue for sure.
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Originally-From: Helmut Schaa <helmut.schaa@googlemail.com>
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Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
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---
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--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
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+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
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@@ -158,55 +158,29 @@ void rt2x00queue_align_frame(struct sk_b
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skb_trim(skb, frame_length);
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}
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-void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
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+/*
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+ * H/W needs L2 padding between the header and the paylod if header size
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+ * is not 4 bytes aligned.
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+ */
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+void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int hdr_len)
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{
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- unsigned int payload_length = skb->len - header_length;
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- unsigned int header_align = ALIGN_SIZE(skb, 0);
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- unsigned int payload_align = ALIGN_SIZE(skb, header_length);
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- unsigned int l2pad = payload_length ? L2PAD_SIZE(header_length) : 0;
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+ unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0;
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- /*
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- * Adjust the header alignment if the payload needs to be moved more
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- * than the header.
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- */
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- if (payload_align > header_align)
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- header_align += 4;
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-
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- /* There is nothing to do if no alignment is needed */
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- if (!header_align)
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+ if (!l2pad)
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return;
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- /* Reserve the amount of space needed in front of the frame */
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- skb_push(skb, header_align);
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-
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- /*
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- * Move the header.
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- */
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- memmove(skb->data, skb->data + header_align, header_length);
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-
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- /* Move the payload, if present and if required */
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- if (payload_length && payload_align)
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- memmove(skb->data + header_length + l2pad,
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- skb->data + header_length + l2pad + payload_align,
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- payload_length);
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-
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- /* Trim the skb to the correct size */
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- skb_trim(skb, header_length + l2pad + payload_length);
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+ skb_push(skb, l2pad);
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+ memmove(skb->data, skb->data + l2pad, hdr_len);
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}
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-void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int header_length)
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+void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int hdr_len)
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{
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- /*
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- * L2 padding is only present if the skb contains more than just the
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- * IEEE 802.11 header.
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- */
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- unsigned int l2pad = (skb->len > header_length) ?
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- L2PAD_SIZE(header_length) : 0;
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+ unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0;
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if (!l2pad)
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return;
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- memmove(skb->data + l2pad, skb->data, header_length);
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+ memmove(skb->data + l2pad, skb->data, hdr_len);
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skb_pull(skb, l2pad);
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}
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