Re: [PATCH v3 1/2] serial: earlycon: add uart_clk_freq parameter

Markus Probst <[email protected]> Sun, 12 Jul 2026 16:46:00 +0000

Newsgroups	gmane.linux.acpi.devel,gmane.linux.kernel,gmane.linux.serial
Message-ID	<[email protected]>

On Sun, 2026-07-12 at 18:40 +0200, Greg Kroah-Hartman wrote:
> On Sun, Jul 12, 2026 at 04:36:17PM +0000, Markus Probst wrote:
> > On Fri, 2026-07-10 at 14:36 +0200, Greg Kroah-Hartman wrote:
> > > On Mon, Jun 15, 2026 at 12:40:21AM +0000, Markus Probst wrote:
> > > > Add function `setup_earlycon_with_uartclk`. This allows the
> > > > options string to be reused with `add_preferred_console`, while still
> > > > allowing to set the uart clock frequency. This will be used in the
> > > > following commit ("ACPI: SPCR: Support UART clock frequency field").
> > > > 
> > > > No logical change intended.
> > > > 
> > > > Signed-off-by: Markus Probst <[email protected]>
> > > > ---
> > > >  drivers/tty/serial/earlycon.c | 17 ++++++++++++-----
> > > >  include/linux/serial_core.h   | 11 +++++++++--
> > > >  2 files changed, 21 insertions(+), 7 deletions(-)
> > > > 
> > > > diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
> > > > index ab9af37f6cda..5a20fe9e3fb6 100644
> > > > --- a/drivers/tty/serial/earlycon.c
> > > > +++ b/drivers/tty/serial/earlycon.c
> > > > @@ -135,11 +135,14 @@ static int __init parse_options(struct earlycon_device *device, char *options)
> > > >  	return 0;
> > > >  }
> > > >  
> > > > -static int __init register_earlycon(char *buf, const struct earlycon_id *match)
> > > > +static int __init register_earlycon(char *buf, unsigned int uart_clk_freq,
> > > > +				    const struct earlycon_id *match)
> > > >  {
> > > >  	int err;
> > > >  	struct uart_port *port = &early_console_dev.port;
> > > >  
> > > > +	port->uartclk = uart_clk_freq;
> > > 
> > > This looks like a logical change, the code today does not do that
> > > anywhere, right?
> > 
> > `register_earlycon` only gets executed once.
> > Thus early_console_dev.port->uartclk is always 0.
> > Since all current callers in this patch series use `setup_earlycon`,
> > the uart_clk_freq parameter is also always 0.
> > 
> > So in case of behaviour/logic, this line does nothing without the 2.
> > patch.
> 
> Then it belongs in the second patch, right?
No.

It does nothing, because the newly added function
`setup_earlycon_with_uartclk` isn't used yet (first caller in the
second patch).

Moving this line in the second patch, would make the
`setup_earlycon_with_uartclk` function obsolete.

Thanks
- Markus Probst

> 
> thanks,
> 
> greg k-h

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