linux-kernel - [PATCH v2] earlycon: initialise baud field of earlycon device structure

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Date:   Thu, 17 Aug 2017 21:08:54 +0300
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     linux-serial@...r.kernel.org
Cc:     linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Subject: [PATCH v2] earlycon: initialise baud field of earlycon device structure

For now baud field of earlycon structure device is't initialised at all
in of_setup_earlycon (in oppositе to register_earlycon).

So when I use stdout-path to point earlycon device
(like stdout-path = &serial or stdout-path = "serial:115200n8")
baud field of earlycon device structure remains uninitialised and
earlycon initialization is not performed correctly as
of_setup_earlycon is used.
When pass all arguments via bootargs
(like bootargs = "earlycon=uart8250,mmio32,0xf0005000,115200n8")
initialization is performed correctly as register_earlycon is used.

So initialise baud field of earlycon device structure by value of
"current-speed" property from device tree or from options
(if they exist) when we use of_setup_earlycon

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
---
Changes v1 -> v2:
 * Use standart property name "current-speed" instead of custom "baud"

NOTE:
I don't add parsing of the other standard options here because we don't
have any place to store them. When we parce and set options of the 'real'
uart device (using uart_parse_options + uart_set_options) we populate
ktermios structure an pass it to port->ops->set_termios callback of
uart_port structure. So it is processing by uart driver itself. But we don't
register such callbacks for earlycon. So we are only able to parse baud
value, which can be stored in baud field of earlycon_device structure.

 drivers/tty/serial/earlycon.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index c365154..93f15e2 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -240,6 +240,7 @@ int __init of_setup_earlycon(const struct earlycon_id *match,
 {
 	int err;
 	struct uart_port *port = &early_console_dev.port;
+	unsigned long baud;
 	const __be32 *val;
 	bool big_endian;
 	u64 addr;
@@ -282,7 +283,15 @@ int __init of_setup_earlycon(const struct earlycon_id *match,
 		}
 	}

+	val = of_get_flat_dt_prop(node, "current-speed", NULL);
+	if (val)
+		early_console_dev.baud = be32_to_cpu(*val);
+
 	if (options) {
+		err = kstrtoul(options, 10, &baud);
+		if (!err)
+			early_console_dev.baud = baud;
+
 		strlcpy(early_console_dev.options, options,
 			sizeof(early_console_dev.options));
 	}
-- 
2.9.3