[PATCH] Revert "serial: 8250: Clear CON_PRINTBUFFER on port re-registration"

[PATCH] Revert "serial: 8250: Clear CON_PRINTBUFFER on port re-registration"

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@baidu.com>

This reverts commit d338ab1d90603f875c4f7ed223406535378173a5.

This may cause some boot logs to be lost on some platforms.

Reported-by: Mark Brown <broonie@kernel.org>
Reported-by: Anirudh Srinivasan <asrinivasan@oss.tenstorrent.com>
Link: https://lore.kernel.org/all/20260522101042.21976-1-fushuai.wang@linux.dev/
Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
---
 drivers/tty/serial/8250/8250_core.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index c0e8a4efbdcc..f49862d90eeb 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -720,12 +720,8 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 	/* Preserve specified console flow control. */
 	cons_flow = uart_cons_flow_enabled(&uart->port);
 
-	if (uart->port.dev) {
-		if (uart_console(&uart->port))
-			uart->port.cons->flags &= ~CON_PRINTBUFFER;
-
+	if (uart->port.dev)
 		uart_remove_one_port(&serial8250_reg, &uart->port);
-	}
 
 	uart->port.ctrl_id	= up->port.ctrl_id;
 	uart->port.port_id	= up->port.port_id;
-- 
2.36.1

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

[John Ogness]

On 2026-07-24, Fushuai Wang <fushuai.wang@linux.dev> wrote:
> From: Fushuai Wang <wangfushuai@baidu.com>
>
> This reverts commit d338ab1d90603f875c4f7ed223406535378173a5.
>
> This may cause some boot logs to be lost on some platforms.
>
> Reported-by: Mark Brown <broonie@kernel.org>
> Reported-by: Anirudh Srinivasan <asrinivasan@oss.tenstorrent.com>
> Link: https://lore.kernel.org/all/20260522101042.21976-1-fushuai.wang@linux.dev/
> Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>

Reviewed-by: John Ogness <john.ogness@linutronix.de>

I also recently stumbled on commmit d338ab1d9060 ("serial: 8250: Clear
CON_PRINTBUFFER on port re-registration") and was surprised to see it
was accepted.

If the double-printing is happening for certain cases with 8250_pnp, I
would expect 8250_pnp (not 8250_core) to detect and handle that
case. 8250_core is the base for a lot of 8250 variants.

John Ogness

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

[Greg KH]

On Fri, Jul 24, 2026 at 03:24:52PM +0800, Fushuai Wang wrote:
> From: Fushuai Wang <wangfushuai@baidu.com>
> 
> This reverts commit d338ab1d90603f875c4f7ed223406535378173a5.

What tree has this commit?

> This may cause some boot logs to be lost on some platforms.

Can we get some more information than that here?

thanks,

greg k-h

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

[John Ogness]

On 2026-07-24, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Fri, Jul 24, 2026 at 03:24:52PM +0800, Fushuai Wang wrote:
>> From: Fushuai Wang <wangfushuai@baidu.com>
>> 
>> This reverts commit d338ab1d90603f875c4f7ed223406535378173a5.
>
> What tree has this commit?

tty/tty-next
tty/tty-testing

John

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

[Mark Brown]

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On Fri, Jul 24, 2026 at 10:36:26AM +0200, Greg KH wrote:
> On Fri, Jul 24, 2026 at 03:24:52PM +0800, Fushuai Wang wrote:

> > This may cause some boot logs to be lost on some platforms.

> Can we get some more information than that here?

I think that's:

  https://lore.kernel.org/r/120da946-505c-4423-a39a-f64f1532a4a7@sirena.org.uk

(causes boot regressions on a range of platforms)

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