netdev - [PATCH net-next 5/7] r8169: improve interrupt coalescing parameter handling

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Date:   Thu, 30 Apr 2020 21:58:06 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net-next 5/7] r8169: improve interrupt coalescing parameter
 handling

The chip supports only frame limits 0, 4, 8, .. 60 internally.
Returning EINVAL for all val % 4 != 0 seems to be a little bit too
unfriendly to the user. Therefore round up the frame limit to the next
supported value. In addition round up the time limit, else a very low
limit could be rounded down to 0, and interpreted as "ignore value"
by the chip.

Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/ethernet/realtek/r8169_main.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index a95615684..fe95c47e7 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -1909,21 +1909,21 @@ static int rtl_set_coalesce(struct net_device *dev, struct ethtool_coalesce *ec)
 		 * - then user does `ethtool -C eth0 rx-usecs 100`
 		 *
 		 * since ethtool sends to kernel whole ethtool_coalesce
-		 * settings, if we do not handle rx_usecs=!0, rx_frames=1
-		 * we'll reject it below in `frames % 4 != 0`.
+		 * settings, if we want to ignore rx_frames then it has
+		 * to be set to 0.
 		 */
 		if (p->frames == 1) {
 			p->frames = 0;
 		}
 
-		units = p->usecs * 1000 / scale;
-		if (p->frames > RTL_COALESCE_FRAME_MAX || p->frames % 4)
-			return -EINVAL;
+		units = DIV_ROUND_UP(p->usecs * 1000, scale);
+		if (p->frames > RTL_COALESCE_FRAME_MAX)
+			return -ERANGE;
 
 		w <<= RTL_COALESCE_SHIFT;
 		w |= units;
 		w <<= RTL_COALESCE_SHIFT;
-		w |= p->frames >> 2;
+		w |= DIV_ROUND_UP(p->frames, 4);
 	}
 
 	rtl_lock_work(tp);
-- 
2.26.2