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r8152: limit the RX buffer size of RTL8153A for USB 2.0

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[ Upstream commit f91a50d8b5 ]

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: ec5791c202 ("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>
This commit is contained in:
Hayes Wang
2021-03-19 15:37:21 +08:00
committed by Greg Kroah-Hartman
parent 048d0bf8ad
commit 1f103ca31c
1 changed files with 4 additions and 1 deletions
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5
drivers/net/usb/r8152.c
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@@ -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;