linux-kernel - [PATCH v4 2/9] serial: sc16is7xx: add post reset delay

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Message-Id: <20230529140711.896830-3-hugo@hugovil.com>
Date:   Mon, 29 May 2023 10:07:04 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     gregkh@...uxfoundation.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        jirislaby@...nel.org, jringle@...dpoint.com,
        l.perczak@...lintechnologies.com, tomasz.mon@...lingroup.com
Cc:     linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, hugo@...ovil.com,
        linux-gpio@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: [PATCH v4 2/9] serial: sc16is7xx: add post reset delay

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

Make sure we wait at least 3us before initiating communication with
the device after reset.

Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
 drivers/tty/serial/sc16is7xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index fbaadec557d8..24c9336f6ab2 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1428,6 +1428,12 @@ static int sc16is7xx_probe(struct device *dev,
 	regmap_write(s->regmap, SC16IS7XX_IOCONTROL_REG << SC16IS7XX_REG_SHIFT,
 			SC16IS7XX_IOCONTROL_SRESET_BIT);
 
+	/*
+	 * After reset, the host must wait at least 3us before initializing a
+	 * communication with the device.
+	 */
+	usleep_range(5, 10);
+
 	for (i = 0; i < devtype->nr_uart; ++i) {
 		s->p[i].line		= i;
 		/* Initialize port data */
-- 
2.30.2