[PATCHv3 1/2] drivers: net: davinci_mdio: remove busy loop on wait user access

Max Uvarov
2017-08-11T10:57:40Z

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@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
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