diff mbox series

[5.4,083/111] r8152: limit the RX buffer size of RTL8153A for USB 2.0

Message ID 20210329075617.978652956@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman March 29, 2021, 7:58 a.m. UTC 
From: Hayes Wang <hayeswang@realtek.com>

[ Upstream commit f91a50d8b51b5c8ef1cfb08115a005bba4250507 ]

If the USB host controller is EHCI, the throughput is reduced from
300Mb/s to 60Mb/s, when the rx buffer size is modified from 16K to
32K.

According to the EHCI spec, the maximum size of the qTD is 20K.
Therefore, when the driver uses more than 20K buffer, the latency
time of EHCI would be increased. And, it let the RTL8153A get worse
throughput.

However, the driver uses alloc_pages() for rx buffer, so I limit
the rx buffer to 16K rather than 20K.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=205923
Fixes: ec5791c202ac ("r8152: separate the rx buffer size")
Reported-by: Robert Davies <robdavies1977@gmail.com>
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/usb/r8152.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 486cf511d2bf..f6d643ecaf39 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -5529,7 +5529,10 @@  static int rtl_ops_init(struct r8152 *tp)
 		ops->in_nway		= rtl8153_in_nway;
 		ops->hw_phy_cfg		= r8153_hw_phy_cfg;
 		ops->autosuspend_en	= rtl8153_runtime_enable;
-		tp->rx_buf_sz		= 32 * 1024;
+		if (tp->udev->speed < USB_SPEED_SUPER)
+			tp->rx_buf_sz	= 16 * 1024;
+		else
+			tp->rx_buf_sz	= 32 * 1024;
 		tp->eee_en		= true;
 		tp->eee_adv		= MDIO_EEE_1000T | MDIO_EEE_100TX;
 		break;