Re: [PATCH v3] serial: 8250: Clear CON_PRINTBUFFER on port re-registration

[Andy Shevchenko]

On Mon, Jul 20, 2026 at 10:22 PM Anirudh Srinivasan
<asrinivasan@xxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, May 22, 2026 at 06:10:42PM +0800, Fushuai Wang wrote:

> Seems like this patch was added in next-20261717.

0717

> I'm noticing that this patch is causing no serial output to be visible
> on riscv boards till the uart device is registered. Normally while
> booting, we expect for all the prints made before this to be
> buffered and appear post serial device initialization.
>
> => booti 0x11000000 0x21000000:${initrd_size} 0x31000000
> Moving Image from 0x11000000 to 0x200000, end=1ca6000
> [ 161.301] ## Flattened Device Tree blob at 31000000
> [ 161.302]    Booting using the fdt blob at 0x31000000
> [ 161.307]    Loading Ramdisk to 7653e000, end 7dd81853 ... OK
> [ 161.366]    Loading Device Tree to 0000000076532000, end 000000007653d25d ... OK
>
> Starting kernel ...
>
> [    0.235159] printk: legacy console [ttyS0] enabled
> [    0.238787] /soc/i2c@d401d800/pmic@41: Fixed dependency cycle(s) with /soc/i2c@d401d800/pmic@41/regulators/buck5
>
> Most devs who are debugging might be booting with the earlycon boot
> parameter. If earlycon is present, serial output is present, but
> with earlycon missing (which is what most distros use), I don't get
> any serial output till this point.

Perhaps it's inconvenient. Logically I support using earlycon (I have
noticed a few times in the past double printing of the kernel buffer
to the serial console). So I tend more towards that this patch
actually gives a better experience. However, I haven't given any tag
to it, nor do I object to any improvements or reverting to the old
behaviour — your inconvenience will become mine :-)

Just my 2c.

-- 
With Best Regards,
Andy Shevchenko