linux-kernel - [PATCH 1/3] serial: 8250_early: Add earlycon support for AMD Carrizo / Stoneyridge

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Message-Id: <20180314003655.12141-2-djkurtz@chromium.org>
Date:   Tue, 13 Mar 2018 18:36:53 -0600
From:   Daniel Kurtz <djkurtz@...omium.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     adurbin@...omium.org, Daniel Kurtz <djkurtz@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Marc Gonzalez <marc_gonzalez@...madesigns.com>,
        Douglas Anderson <dianders@...omium.org>,
        Matt Redfearn <matt.redfearn@...s.com>,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        linux-serial@...r.kernel.org (open list:SERIAL DRIVERS),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 1/3] serial: 8250_early: Add earlycon support for AMD Carrizo / Stoneyridge

AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a 48 MHz
input clock.

Allow these platforms to set up this clock by specifying a kernel command
line like:
earlycon=amdcz,mmio32,0xfedc6000,115200

Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
---
 drivers/tty/serial/8250/8250_early.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index ae6a256524d8..c6bf971a6038 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -195,3 +195,18 @@ static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
 
 #endif
+
+#ifdef CONFIG_SERIAL_8250_DW
+static int __init early_amdcz_setup(struct earlycon_device *dev,
+				    const char *opt)
+{
+	struct uart_port *port = &dev->port;
+
+	port->uartclk = 48000000;
+
+	return early_serial8250_setup(dev, opt);
+}
+
+EARLYCON_DECLARE(amdcz, early_amdcz_setup);
+
+#endif
-- 
2.16.2.804.g6dcf76e118-goog