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Message-ID: <54CE53F3.5040709@hurleysoftware.com>
Date: Sun, 01 Feb 2015 11:27:31 -0500
From: Peter Hurley <peter@...leysoftware.com>
To: Eddie Huang <eddie.huang@...iatek.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Matthias Brugger <matthias.bgg@...il.com>
CC: devicetree@...r.kernel.org,
Vladimir Murzin <vladimir.murzin@....com>,
srv_heupstream@...iatek.com, Pawel Moll <pawel.moll@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Jonathan Corbet <corbet@....net>,
Will Deacon <will.deacon@....com>,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
yh.chen@...iatek.com, Howard Chen <ibanezchen@...il.com>,
Ashwin Chaugule <ashwin.chaugule@...aro.org>,
linux-serial@...r.kernel.org, Kumar Gala <galak@...eaurora.org>,
"Joe.C" <yingjoe.chen@...iatek.com>, Jiri Slaby <jslaby@...e.cz>,
linux-arm-kernel@...ts.infradead.org,
Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH v2 1/4] tty: serial: Add 8250 earlycon to support noinit
option
Hi Eddie,
On 01/12/2015 08:08 AM, Eddie Huang wrote:
> Add earlycon support not only baudrate option, but also add noinit option.
> If use noinit option, 8250 earlycon will not init serial hardware and use
> loader setting.
I see this went into Greg's tty-testing branch.
The only point of this is to not program the divisor, right?
I ask because early_serial8250_setup() could already handle this without
extra options by simply not doing divisor programming if no baud option is
present.
And this blows up if the optional console= form is used:
console=uart,mmio32,<addr>,noinit
because the ttyS console will expect line settings for console match.
Regards,
Peter Hurley
> Signed-off-by: Eddie Huang <eddie.huang@...iatek.com>
> ---
> drivers/tty/serial/8250/8250_early.c | 7 ++++---
> drivers/tty/serial/earlycon.c | 17 ++++++++++++-----
> include/linux/serial_8250.h | 2 ++
> include/linux/serial_core.h | 1 +
> 4 files changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> index 4858b8a..a13d757 100644
> --- a/drivers/tty/serial/8250/8250_early.c
> +++ b/drivers/tty/serial/8250/8250_early.c
> @@ -138,19 +138,20 @@ static void __init init_port(struct earlycon_device *device)
> serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
> }
>
> -static int __init early_serial8250_setup(struct earlycon_device *device,
> +int __init early_serial8250_setup(struct earlycon_device *device,
> const char *options)
> {
> if (!(device->port.membase || device->port.iobase))
> return 0;
>
> - if (!device->baud) {
> + if (!device->baud && !device->noinit) {
> device->baud = probe_baud(&device->port);
> snprintf(device->options, sizeof(device->options), "%u",
> device->baud);
> }
>
> - init_port(device);
> + if (!device->noinit)
> + init_port(device);
>
> early_device = device;
> device->con->write = early_serial8250_write;
> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
> index 64fe25a..4891251 100644
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -58,7 +58,7 @@ static int __init parse_options(struct earlycon_device *device,
> char *options)
> {
> struct uart_port *port = &device->port;
> - int mmio, mmio32, length;
> + int noinit, mmio, mmio32, length;
> unsigned long addr;
>
> if (!options)
> @@ -92,10 +92,17 @@ static int __init parse_options(struct earlycon_device *device,
> options = strchr(options, ',');
> if (options) {
> options++;
> - device->baud = simple_strtoul(options, NULL, 0);
> - length = min(strcspn(options, " ") + 1,
> - (size_t)(sizeof(device->options)));
> - strlcpy(device->options, options, length);
> + noinit = !strncmp(options, "noinit", 6);
> + if (noinit) {
> + device->noinit = noinit;
> + strlcpy(device->options, options, 6);
> + device->options[6] = '\0';
> + } else {
> + device->baud = simple_strtoul(options, NULL, 0);
> + length = min(strcspn(options, " ") + 1,
> + (size_t)(sizeof(device->options)));
> + strlcpy(device->options, options, length);
> + }
> }
>
> if (port->iotype == UPIO_MEM || port->iotype == UPIO_MEM32)
> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
> index e02acf0..0e26eec 100644
> --- a/include/linux/serial_8250.h
> +++ b/include/linux/serial_8250.h
> @@ -119,6 +119,8 @@ extern int serial8250_find_port(struct uart_port *p);
> extern int serial8250_find_port_for_earlycon(void);
> extern unsigned int serial8250_early_in(struct uart_port *port, int offset);
> extern void serial8250_early_out(struct uart_port *port, int offset, int value);
> +extern int early_serial8250_setup(struct earlycon_device *device,
> + const char *options);
> extern int setup_early_serial8250_console(char *cmdline);
> extern void serial8250_do_set_termios(struct uart_port *port,
> struct ktermios *termios, struct ktermios *old);
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 057038c..72c6698 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -326,6 +326,7 @@ struct earlycon_device {
> struct uart_port port;
> char options[16]; /* e.g., 115200n8 */
> unsigned int baud;
> + int noinit;
> };
> int setup_earlycon(char *buf, const char *match,
> int (*setup)(struct earlycon_device *, const char *));
>
--
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