linux-kernel - [PATCH 3.16 203/254] usb: misc: usb3503: make sure reset is low for at least 100us

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Message-ID: <lsq.1519831218.304488537@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Stefan Agner" <stefan@...er.ch>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 203/254] usb: misc: usb3503: make sure reset is low
 for at least 100us

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Agner <stefan@...er.ch>

commit b8626f1dc29d3eee444bfaa92146ec7b291ef41c upstream.

When using a GPIO which is high by default, and initialize the
driver in USB Hub mode, initialization fails with:
  [  111.757794] usb3503 0-0008: SP_ILOCK failed (-5)

The reason seems to be that the chip is not properly reset.
Probe does initialize reset low, however some lines later the
code already set it back high, which is not long enouth.

Make sure reset is asserted for at least 100us by inserting a
delay after initializing the reset pin during probe.

Signed-off-by: Stefan Agner <stefan@...er.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/misc/usb3503.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/misc/usb3503.c
+++ b/drivers/usb/misc/usb3503.c
@@ -292,6 +292,8 @@ static int usb3503_probe(struct usb3503
 	if (gpio_is_valid(hub->gpio_reset)) {
 		err = devm_gpio_request_one(dev, hub->gpio_reset,
 				GPIOF_OUT_INIT_LOW, "usb3503 reset");
+		/* Datasheet defines a hardware reset to be at least 100us */
+		usleep_range(100, 10000);
 		if (err) {
 			dev_err(dev,
 				"unable to request GPIO %d as reset pin (%d)\n",