Hi Peter,

On Sun, 2015-02-01 at 11:27 -0500, Peter Hurley wrote:

Hi Eddie,

On 01/12/2015 08:08 AM, Eddie Huang wrote:

quoted

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?

In this case, yes.

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.

MTK support high speed UART, which means baudrate can be more than
115200. You can reference mtk8250_set_termios() function in 8250_mtk.c.
Unfortunately, the early_serial8250_setup() can not handle high speed
case. This is why I add noinit parameter.

Besides, I think "no baud option" is a little tricky, and maybe someday
someone not only care about divisor, but also flow. Legacy earlyprintk
and other uart drivers like msm_serial.c also don't init uart hardware.

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.

Yes, you are right. console parameter case will fail, I only consider
earlycon parameter case.

quoted

Signed-off-by: Eddie Huang <eddie.huang@mediatek.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(-)