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From: Mike Looijmans <mike.looijmans@topic.nl>
To: netdev@vger.kernel.org
Cc: Mike Looijmans <mike.looijmans@topic.nl>,
	Andrew Lunn <andrew@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] net: mdiobus: Prevent spike on MDIO bus reset signal
Date: Tue, 26 Jan 2021 08:33:37 +0100	[thread overview]
Message-ID: <20210126073337.20393-1-mike.looijmans@topic.nl> (raw)

The mdio_bus reset code first de-asserted the reset by allocating with
GPIOD_OUT_LOW, then asserted and de-asserted again. In other words, if
the reset signal defaulted to asserted, there'd be a short "spike"
before the reset.

Instead, directly assert the reset signal using GPIOD_OUT_HIGH, this
removes the spike and also removes a line of code since the signal
is already high.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>

---

 drivers/net/phy/mdio_bus.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 2b42e46066b4..34e98ae75110 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -543,8 +543,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 	mutex_init(&bus->mdio_lock);
 	mutex_init(&bus->shared_lock);
 
-	/* de-assert bus level PHY GPIO reset */
-	gpiod = devm_gpiod_get_optional(&bus->dev, "reset", GPIOD_OUT_LOW);
+	/* assert bus level PHY GPIO reset */
+	gpiod = devm_gpiod_get_optional(&bus->dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(gpiod)) {
 		err = dev_err_probe(&bus->dev, PTR_ERR(gpiod),
 				    "mii_bus %s couldn't get reset GPIO\n",
@@ -553,8 +553,6 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 		return err;
 	} else	if (gpiod) {
 		bus->reset_gpiod = gpiod;
-
-		gpiod_set_value_cansleep(gpiod, 1);
 		fsleep(bus->reset_delay_us);
 		gpiod_set_value_cansleep(gpiod, 0);
 		if (bus->reset_post_delay_us > 0)
-- 
2.17.1


             reply	other threads:[~2021-01-26 17:32 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-26  7:33 Mike Looijmans [this message]
2021-01-26 13:14 ` [PATCH] net: mdiobus: Prevent spike on MDIO bus reset signal Andrew Lunn
2021-01-26 13:49   ` Russell King - ARM Linux admin
     [not found]     ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.b4d05392-d8bb-4828-9ac6-5a63736d3625@emailsignatures365.codetwo.com>
     [not found]       ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.23e4b566-2e4d-4160-a40f-4bf79ef86f8a@emailsignatures365.codetwo.com>
2021-01-27  7:08         ` Mike Looijmans
2021-01-27 22:54           ` Jakub Kicinski
2021-01-28  0:00     ` Andrew Lunn
2021-01-28  0:25       ` Russell King - ARM Linux admin
2021-01-28  1:12         ` Andrew Lunn
     [not found]           ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.47109184-a5be-4b1d-bb22-724baf83e536@emailsignatures365.codetwo.com>
     [not found]             ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.a2a17a1f-7cb0-46c3-bdd8-65266e08a153@emailsignatures365.codetwo.com>
2021-02-02 11:40               ` Mike Looijmans
2021-02-02 13:51                 ` Andrew Lunn
2021-01-28  1:56 ` Andrew Lunn
     [not found]   ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.7228ddf2-6794-42a0-8b0b-3821446cdb40@emailsignatures365.codetwo.com>
     [not found]     ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.7855d092-e2c3-4ba5-a029-2a0bbce637e1@emailsignatures365.codetwo.com>
2021-01-28  8:45       ` Mike Looijmans
2021-01-29 20:23         ` Andrew Lunn

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