From: P33M Date: Wed, 1 May 2019 16:04:32 +0000 (+0100) Subject: smsc95xx: dynamically fix up TX buffer alignment with padding bytes X-Git-Tag: accepted/tizen/unified/20190614.051536~196 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=96b972dc736d943f371a16ccca452a053d83c65b;p=platform%2Fkernel%2Flinux-rpi3.git 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 --- diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index a5bbec7..c087b6d 100644 --- a/drivers/net/usb/smsc95xx.c +++ b/drivers/net/usb/smsc95xx.c @@ -2082,7 +2082,9 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev, 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(struct usbnet *dev, } } - 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); diff --git a/drivers/net/usb/smsc95xx.h b/drivers/net/usb/smsc95xx.h index cfc704f..55f9f03 100644 --- 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 */