This is a note to let you know that I've just added the patch titled r8152: limit the RX buffer size of RTL8153A for USB 2.0 to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: r8152-limit-the-rx-buffer-size-of-rtl8153a-for-usb-2.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit dcc4bf80a82a5b852b841e26db465692b0090651 Author: Hayes Wang <hayeswang@xxxxxxxxxxx> Date: Fri Mar 19 15:37:21 2021 +0800 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 <robdavies1977@xxxxxxxxx> Signed-off-by: Hayes Wang <hayeswang@xxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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;