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From: John Efstathiades <john.efstathiades@pebblebay.com>
To: unlisted-recipients:; (no To-header on input)
Cc: UNGLinuxDriver@microchip.com, woojung.huh@microchip.com,
	davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org,
	linux-usb@vger.kernel.org, john.efstathiades@pebblebay.com
Subject: [PATCH net-next v2 03/10] lan78xx: Set flow control threshold to prevent packet loss
Date: Tue, 24 Aug 2021 19:56:06 +0100	[thread overview]
Message-ID: <20210824185613.49545-4-john.efstathiades@pebblebay.com> (raw)
In-Reply-To: <20210824185613.49545-1-john.efstathiades@pebblebay.com>

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 <john.efstathiades@pebblebay.com>
---
 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"),
-- 
2.25.1


  parent reply	other threads:[~2021-08-24 18:57 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 18:56 [PATCH net-next v2 00/10] LAN7800 driver improvements John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 01/10] lan78xx: Fix white space and style issues John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 02/10] lan78xx: Remove unused timer John Efstathiades
2021-08-24 18:56 ` John Efstathiades [this message]
2021-08-24 18:56 ` [PATCH net-next v2 04/10] lan78xx: Remove unused pause frame queue John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 05/10] lan78xx: Add missing return code checks John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 06/10] lan78xx: Fix exception on link speed change John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 07/10] lan78xx: Fix partial packet errors on suspend/resume John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 08/10] lan78xx: Fix race conditions in suspend/resume handling John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 09/10] lan78xx: Fix race condition in disconnect handling John Efstathiades
2021-08-24 18:56 ` [PATCH net-next v2 10/10] lan78xx: Limit number of driver warning messages John Efstathiades
2021-08-25 10:00 ` [PATCH net-next v2 00/10] LAN7800 driver improvements patchwork-bot+netdevbpf

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