linux-kernel - [PATCH] Adding proper request of GPIO used by cpm

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Date:	Wed, 21 Aug 2013 17:59:24 +0200
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
CC:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] Adding proper request of GPIO used by cpm_uart driver

cpm_uart serial driver uses GPIO for control signals. In order to be used
properly, GPIOs have to be reserved. Comment in gpiolib.c considers illegal
the use of GPIOs without requesting them. In addition, the direction of the
GPIO has to be set properly.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

diff -ur linux-3.8.13/drivers/tty/serial/cpm_uart/cpm_uart_core.c linux/drivers/tty/serial/cpm_uart/cpm_uart_core.c
--- linux-3.8.13/drivers/tty/serial/cpm_uart/cpm_uart_core.c	2013-08-21 05:34:03.000000000 +0200
+++ linux/drivers/tty/serial/cpm_uart/cpm_uart_core.c	2013-08-21 05:30:04.000000000 +0200
@@ -1213,8 +1213,32 @@
 		goto out_pram;
 	}
 
-	for (i = 0; i < NUM_GPIOS; i++)
-		pinfo->gpios[i] = of_get_gpio(np, i);
+	for (i = 0; i < NUM_GPIOS; i++) {
+		int gpio;
+
+		pinfo->gpios[i] = -1;
+
+		gpio = of_get_gpio(np, i);
+
+		if (gpio_is_valid(gpio)) {
+			ret = gpio_request(gpio, "cpm_uart");
+			if (ret) {
+				pr_err("can't request gpio #%d: %d\n", i, ret);
+				continue;
+			}
+			if (i == GPIO_RTS || i == GPIO_DTR)
+				ret = gpio_direction_output(gpio, 0);
+			else
+				ret = gpio_direction_input(gpio);
+			if (ret) {
+				pr_err("can't set direction for gpio #%d: %d\n",
+					i, ret);
+				gpio_free(gpio);
+				continue;
+			}
+			pinfo->gpios[i] = gpio;
+		}
+	}
 
 #ifdef CONFIG_PPC_EARLY_DEBUG_CPM
 	udbg_putc = NULL;
--
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