target/linux/brcm2708/patches-4.19/950-0478-smsc95xx-dynamically-fix-up-TX-buffer-alignment-with.patch

   1 From 26c79197da4b2911e10c600d79839a82a43a06ff Mon Sep 17 00:00:00 2001
   2 From: P33M <p33m@github.com>
   3 Date: Wed, 1 May 2019 17:04:32 +0100
   4 Subject: [PATCH 478/806] smsc95xx: dynamically fix up TX buffer alignment with
   5  padding bytes
   6
   7 dwc_otg requires a 32-bit aligned buffer start address, otherwise
   8 expensive bounce buffers are used. The LAN951x hardware can skip up to
   9 3 bytes between the TX header and the start of frame data, which can
  10 be used to force alignment of the URB passed to dwc_otg.
  11
  12 As found in https://github.com/raspberrypi/linux/issues/2924
  13 ---
  14  drivers/net/usb/smsc95xx.c | 12 +++++++-----
  15  drivers/net/usb/smsc95xx.h |  2 +-
  16  2 files changed, 8 insertions(+), 6 deletions(-)
  17
  18 --- a/drivers/net/usb/smsc95xx.c
  19 +++ b/drivers/net/usb/smsc95xx.c
  20 @@ -2082,7 +2082,9 @@ static struct sk_buff *smsc95xx_tx_fixup
  21                                          struct sk_buff *skb, gfp_t flags)
  22  {
  23         bool csum = skb->ip_summed == CHECKSUM_PARTIAL;
  24 -       int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM : SMSC95XX_TX_OVERHEAD;
  25 +       unsigned int align_bytes = -((uintptr_t)skb->data) & 0x3;
  26 +       int overhead = csum ? SMSC95XX_TX_OVERHEAD_CSUM + align_bytes
  27 +                               : SMSC95XX_TX_OVERHEAD + align_bytes;
  28         u32 tx_cmd_a, tx_cmd_b;
  29
  30         /* We do not advertise SG, so skbs should be already linearized */
  31 @@ -2116,16 +2118,16 @@ static struct sk_buff *smsc95xx_tx_fixup
  32                 }
  33         }
  34
  35 -       skb_push(skb, 4);
  36 -       tx_cmd_b = (u32)(skb->len - 4);
  37 +       skb_push(skb, 4 + align_bytes);
  38 +       tx_cmd_b = (u32)(skb->len - 4 - align_bytes);
  39         if (csum)
  40                 tx_cmd_b |= TX_CMD_B_CSUM_ENABLE;
  41         cpu_to_le32s(&tx_cmd_b);
  42         memcpy(skb->data, &tx_cmd_b, 4);
  43
  44         skb_push(skb, 4);
  45 -       tx_cmd_a = (u32)(skb->len - 8) | TX_CMD_A_FIRST_SEG_ |
  46 -               TX_CMD_A_LAST_SEG_;
  47 +       tx_cmd_a = (u32)(skb->len - 8 - align_bytes) | TX_CMD_A_FIRST_SEG_ |
  48 +               (align_bytes << 16) | TX_CMD_A_LAST_SEG_;
  49         cpu_to_le32s(&tx_cmd_a);
  50         memcpy(skb->data, &tx_cmd_a, 4);
  51
  52 --- a/drivers/net/usb/smsc95xx.h
  53 +++ b/drivers/net/usb/smsc95xx.h
  54 @@ -21,7 +21,7 @@
  55  #define _SMSC95XX_H
  56
  57  /* Tx command words */
  58 -#define TX_CMD_A_DATA_OFFSET_  (0x001F0000)    /* Data Start Offset */
  59 +#define TX_CMD_A_DATA_OFFSET_  (0x00030000)    /* Data Start Offset */
  60  #define TX_CMD_A_FIRST_SEG_    (0x00002000)    /* First Segment */
  61  #define TX_CMD_A_LAST_SEG_     (0x00001000)    /* Last Segment */
  62  #define TX_CMD_A_BUF_SIZE_     (0x000007FF)    /* Buffer Size */