From e303bfb934b2a5adb549b43bbd51b1a0e33c33b3 Mon Sep 17 00:00:00 2001 From: P33M 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 */