netdev - [PATCHv2 1/2] drivers: net: davinci_mdio: remove busy loop on wait user access

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Message-Id: <1502351267-23841-1-git-send-email-muvarov@gmail.com>
Date:   Thu, 10 Aug 2017 10:47:46 +0300
From:   Max Uvarov <muvarov@...il.com>
To:     netdev@...r.kernel.org
Cc:     linux-omap@...r.kernel.org, grygorii.strashko@...com,
        Max Uvarov <muvarov@...il.com>
Subject: [PATCHv2 1/2] drivers: net: davinci_mdio: remove busy loop on wait user access

Polling 14 mdio devices on single mdio bus eats 30% of 1Ghz cpu time
due to busy loop in wait(). Add small delay to relax cpu.

Signed-off-by: Max Uvarov <muvarov@...il.com>
---
 v2: fix spelling in commit description.

 drivers/net/ethernet/ti/davinci_mdio.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c
index 33df340..611e7cc 100644
--- a/drivers/net/ethernet/ti/davinci_mdio.c
+++ b/drivers/net/ethernet/ti/davinci_mdio.c
@@ -198,8 +198,10 @@ static inline int wait_for_user_access(struct davinci_mdio_data *data)
 			return 0;
 
 		reg = __raw_readl(&regs->control);
-		if ((reg & CONTROL_IDLE) == 0)
+		if ((reg & CONTROL_IDLE) == 0) {
+			usleep_range(100, 200);
 			continue;
+		}
 
 		/*
 		 * An emac soft_reset may have clobbered the mdio controller's
-- 
2.5.0