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 --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c index fd5ca11c4cbb..390d9e1fa7fe 100644 --- a/drivers/net/usb/r8152.c +++ b/drivers/net/usb/r8152.c @@ -6502,7 +6502,10 @@ 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;