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 <[email protected]>
> ---
> 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 *));
>
On 02/01/2015 11:27 AM, Peter Hurley wrote:
> 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.
Does the patch below work for your use-case?
[ Note: the patch applies to 3.19-rcX. To test, your noinit patches need to be
reverted first.
]
--- >% ---
From: Peter Hurley <[email protected]>
Subject: [PATCH] serial: 8250_early: Assume uart already initialized if no
baud option
The <baud><parity><bit> option string is not supplied if the earlycon
is started via devicetree and OF_EARLYCON_DECLARE(). The option string
is also not required if started via kernel command line parameters of
the form:
earlycon=uart,mmio,<addr>
console=uart,mmio,<addr>
If earlycon_device->baud is 0, then an option string was not supplied.
In this case, assume the uart has already been initialized by the
bootloader or firmware.
Signed-off-by: Peter Hurley <[email protected]>
---
drivers/tty/serial/8250/8250_early.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index d7b831b..1701d00 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -149,12 +149,18 @@ static int __init early_serial8250_setup(struct earlycon_device *device,
return 0;
if (!device->baud) {
+ struct uart_port *port = &device->port;
+ unsigned int ier;
+
device->baud = probe_baud(&device->port);
snprintf(device->options, sizeof(device->options), "%u",
device->baud);
- }
- init_port(device);
+ /* assume the device was initialized, only mask interrupts */
+ ier = serial8250_early_in(port, UART_IER);
+ serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
+ } else
+ init_port(device);
device->con->write = early_serial8250_write;
return 0;
--
2.2.2