[PATCH net-next 03/10] lan78xx: Set flow control threshold to prevent packet loss
From: John Efstathiades <hidden>
Date: 2021-08-23 13:53:43
Subsystem:
networking drivers, the rest, usb lan78xx ethernet driver, usb networking drivers · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Thangaraj Samynathan, Rengarajan Sundararajan
Set threshold at which flow control is triggered to 3/4 full of the internal Rx packet FIFO to prevent packet drops at high data rates. The new setting reduces the number of dropped UDP frames and TCP retransmit requests especially on less capable CPUs. Signed-off-by: John Efstathiades <redacted> --- drivers/net/usb/lan78xx.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 2896d31e5573..ccfb2d47932d 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c@@ -46,6 +46,19 @@ #define MAX_RX_FIFO_SIZE (12 * 1024) #define MAX_TX_FIFO_SIZE (12 * 1024) + +#define FLOW_THRESHOLD(n) ((((n) + 511) / 512) & 0x7F) +#define FLOW_CTRL_THRESHOLD(on, off) ((FLOW_THRESHOLD(on) << 0) | \ + (FLOW_THRESHOLD(off) << 8)) + +/* Flow control turned on when Rx FIFO level rises above this level (bytes) */ +#define FLOW_ON_SS 9216 +#define FLOW_ON_HS 8704 + +/* Flow control turned off when Rx FIFO level falls below this level (bytes) */ +#define FLOW_OFF_SS 4096 +#define FLOW_OFF_HS 1024 + #define DEFAULT_BURST_CAP_SIZE (MAX_TX_FIFO_SIZE) #define DEFAULT_BULK_IN_DELAY (0x0800) #define MAX_SINGLE_PACKET_SIZE (9000)
@@ -1135,9 +1148,9 @@ static int lan78xx_update_flowcontrol(struct lan78xx_net *dev, u8 duplex, flow |= FLOW_CR_RX_FCEN_; if (dev->udev->speed == USB_SPEED_SUPER) - fct_flow = 0x817; + fct_flow = FLOW_CTRL_THRESHOLD(FLOW_ON_SS, FLOW_OFF_SS); else if (dev->udev->speed == USB_SPEED_HIGH) - fct_flow = 0x211; + fct_flow = FLOW_CTRL_THRESHOLD(FLOW_ON_HS, FLOW_OFF_HS); netif_dbg(dev, link, dev->net, "rx pause %s, tx pause %s", (cap & FLOW_CTRL_RX ? "enabled" : "disabled"),
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2.25.1