linux-kernel - [PATCH] serial: 8250_uniphier: add earlycon support

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Message-Id: <1445503154-14340-1-git-send-email-yamada.masahiro@socionext.com>
Date:	Thu, 22 Oct 2015 17:39:14 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	linux-serial@...r.kernel.org
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Jiri Slaby <jslaby@...e.com>, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] serial: 8250_uniphier: add earlycon support

This reuses the code of drivers/tty/serial/8250/8250_early.c except

  - Overwrite device->port.iotype and device->port.regshift for
    UPIO_MEM32 because of_setup_earlycon() has set them for UPIO_MEM.

  - Set device->baud to zero to prevent early8250_setup() from
    initializing the divisor register because port->uartclk does not
    match the frequency expected by this hardware.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 drivers/tty/serial/8250/8250_uniphier.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_uniphier.c b/drivers/tty/serial/8250/8250_uniphier.c
index 245edbb..c1075c5 100644
--- a/drivers/tty/serial/8250/8250_uniphier.c
+++ b/drivers/tty/serial/8250/8250_uniphier.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/console.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -34,6 +35,29 @@ struct uniphier8250_priv {
 	spinlock_t atomic_write_lock;
 };
 
+#if IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE)
+static int __init uniphier_early_console_setup(struct earlycon_device *device,
+					       const char *options)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+
+	/* This hardware always expects MMIO32 register interface. */
+	device->port.iotype = UPIO_MEM32;
+	device->port.regshift = 2;
+
+	/*
+	 * Do not touch the divisor register in early_serial8250_setup();
+	 * we assume it has been initialized by a boot loader.
+	 */
+	device->baud = 0;
+
+	return early_serial8250_setup(device, options);
+}
+OF_EARLYCON_DECLARE(uniphier_uart, "socionext,uniphier-uart",
+		    uniphier_early_console_setup);
+#endif
+
 /*
  * The register map is slightly different from that of 8250.
  * IO callbacks must be overridden for correct access to FCR, LCR, and MCR.
-- 
1.9.1

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