2022-11-23 23:44:10

by Ricardo Ribalda

Subject: [PATCH v1 1/1] earlycon: Let users set the clock frequency

Some platforms, namely AMD Picasso, use non standard uart clocks (48M),
witch makes it impossible to use with earlycon.

Let the user select its own frequency.

Signed-off-by: Ricardo Ribalda <[email protected]>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a465d5242774..9efb6c3b0486 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1182,10 +1182,10 @@
specified, the serial port must already be setup and
configured.

- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
- uart[8250],mmio32,<addr>[,options]
- uart[8250],mmio32be,<addr>[,options]
+ uart[8250],io,<addr>[,options[,uartclk]]
+ uart[8250],mmio,<addr>[,options[,uartclk]]
+ uart[8250],mmio32,<addr>[,options[,uartclk]]
+ uart[8250],mmio32be,<addr>[,options[,uartclk]]
uart[8250],0x<addr>[,options]
Start an early, polled-mode console on the 8250/16550
UART at the specified I/O port or MMIO address.
@@ -1194,7 +1194,9 @@
If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
to be equivalent to 'mmio'. 'options' are specified
in the same format described for "console=ttyS<n>"; if
- unspecified, the h/w is not initialized.
+ unspecified, the h/w is not initialized. 'uartclk' is
+ the uart clock frequency; if unspecified, it is set
+ to 'BASE_BAUD' * 16.

pl011,<addr>
pl011,mmio32,<addr>
diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index a5f380584cda..094611dc7209 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -120,7 +120,11 @@ static int __init parse_options(struct earlycon_device *device, char *options)
}

if (options) {
+ char *uartclk;
device->baud = simple_strtoul(options, NULL, 0);
+ uartclk = strchr(options, ',');
+ if (uartclk)
+ port->uartclk = simple_strtoull(uartclk + 1, NULL, 0);
length = min(strcspn(options, " ") + 1,
(size_t)(sizeof(device->options)));
strscpy(device->options, options, length);
@@ -139,7 +143,8 @@ static int __init register_earlycon(char *buf, const struct earlycon_id *match)
buf = NULL;

spin_lock_init(&port->lock);
- port->uartclk = BASE_BAUD * 16;
+ if (!port->uartclk)
+ port->uartclk = BASE_BAUD * 16;
if (port->mapbase)
port->membase = earlycon_map(port->mapbase, 64);


--
b4 0.11.0-dev-d93f8

2022-11-24 06:18:36

by Jiri Slaby

Subject: Re: [PATCH v1 1/1] earlycon: Let users set the clock frequency

Hi,

On 24. 11. 22, 0:29, Ricardo Ribalda wrote:
> Some platforms, namely AMD Picasso, use non standard uart clocks (48M),
> witch makes it impossible to use with earlycon.
>
> Let the user select its own frequency.
...
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -120,7 +120,11 @@ static int __init parse_options(struct earlycon_device *device, char *options)
> }
>
> if (options) {
> + char *uartclk;
> device->baud = simple_strtoul(options, NULL, 0);
> + uartclk = strchr(options, ',');
> + if (uartclk)
> + port->uartclk = simple_strtoull(uartclk + 1, NULL, 0);

uartclk is uint. So why does it make sense to do ull parsing?

thanks,
--
js
suse labs