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From e303bfb934b2a5adb549b43bbd51b1a0e33c33b3 Mon Sep 17 00:00:00 2001
From: P33M <p33m@github.com>
Date: Wed, 1 May 2019 17:04:32 +0100
Subject: [PATCH 484/703] smsc95xx: dynamically fix up TX buffer alignment with
padding bytes
dwc_otg requires a 32-bit aligned buffer start address, otherwise
expensive bounce buffers are used. The LAN951x hardware can skip up to
3 bytes between the TX header and the start of frame data, which can
be used to force alignment of the URB passed to dwc_otg.
As found in https://github.com/raspberrypi/linux/issues/2924
---
drivers/net/usb/smsc95xx.c | 12 +++++++-----
drivers/net/usb/smsc95xx.h | 2 +-
2 files changed, 8 insertions(+), 6 deletions(-)
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -2082,7 +2082,9 @@ static struct sk_buff *smsc95xx_tx_fixup
struct sk_buff *skb, gfp_t flags)
{
bool csum = skb->ip_summed == CHECKSUM_PARTIAL;
- int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM : SMSC95XX_TX_OVERHEAD;
+ unsigned int align_bytes = -((uintptr_t)skb->data) & 0x3;
+ int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM + align_bytes
+ : SMSC95XX_TX_OVERHEAD + align_bytes;
u32 tx_cmd_a, tx_cmd_b;
/* We do not advertise SG, so skbs should be already linearized */
@@ -2116,16 +2118,16 @@ static struct sk_buff *smsc95xx_tx_fixup
}
}
- skb_push(skb, 4);
- tx_cmd_b = (u32)(skb->len - 4);
+ skb_push(skb, 4 + align_bytes);
+ tx_cmd_b = (u32)(skb->len - 4 - align_bytes);
if (csum)
tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
cpu_to_le32s(&tx_cmd_b);
memcpy(skb->data, &tx_cmd_b, 4);
skb_push(skb, 4);
- tx_cmd_a = (u32)(skb->len - 8) | TX_CMD_A_FIRST_SEG_ |
- TX_CMD_A_LAST_SEG_;
+ tx_cmd_a = (u32)(skb->len - 8 - align_bytes) | TX_CMD_A_FIRST_SEG_ |
+ (align_bytes << 16) | TX_CMD_A_LAST_SEG_;
cpu_to_le32s(&tx_cmd_a);
memcpy(skb->data, &tx_cmd_a, 4);
--- a/drivers/net/usb/smsc95xx.h
+++ b/drivers/net/usb/smsc95xx.h
@@ -21,7 +21,7 @@
#define _SMSC95XX_H
/* Tx command words */
-#define TX_CMD_A_DATA_OFFSET_ (0x001F0000) /* Data Start Offset */
+#define TX_CMD_A_DATA_OFFSET_ (0x00030000) /* Data Start Offset */
#define TX_CMD_A_FIRST_SEG_ (0x00002000) /* First Segment */
#define TX_CMD_A_LAST_SEG_ (0x00001000) /* Last Segment */
#define TX_CMD_A_BUF_SIZE_ (0x000007FF) /* Buffer Size */
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