From 1f103ca31c51366a39e215b5bf1c2fd17a0c2601 Mon Sep 17 00:00:00 2001 From: Hayes Wang Date: Fri, 19 Mar 2021 15:37:21 +0800 Subject: [PATCH] r8152: limit the RX buffer size of RTL8153A for USB 2.0 [ 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 Signed-off-by: Hayes Wang Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/net/usb/r8152.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) 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;