netdev - [PATCH 4/4] net: dsa: microchip: Implement recommended reset timing

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Message-Id: <20200905140325.108846-5-pbarker@konsulko.com>
Date:   Sat,  5 Sep 2020 15:03:25 +0100
From:   Paul Barker <pbarker@...sulko.com>
To:     Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Paul Barker <pbarker@...sulko.com>, netdev@...r.kernel.org
Subject: [PATCH 4/4] net: dsa: microchip: Implement recommended reset timing

The datasheet for the ksz9893 and ksz9477 switches recommend waiting at
least 100us after the de-assertion of reset before trying to program the
device through any interface.

Also switch the existing mdelay() call to usleep_range() as recommended
in Documentation/timers/timers-howto.rst. The 2ms range used here is
somewhat arbitrary, as long as the reset is asserted for at least 10ms
we should be ok.

Signed-off-by: Paul Barker <pbarker@...sulko.com>
---
 drivers/net/dsa/microchip/ksz_common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 8d53b12d40a8..a31738662d95 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -400,8 +400,9 @@ int ksz_switch_register(struct ksz_device *dev,
 
 	if (dev->reset_gpio) {
 		gpiod_set_value_cansleep(dev->reset_gpio, 1);
-		mdelay(10);
+		usleep_range(10000, 12000);
 		gpiod_set_value_cansleep(dev->reset_gpio, 0);
+		usleep_range(100, 1000);
 	}
 
 	mutex_init(&dev->dev_mutex);
-- 
2.28.0