[PATCH v1 0/1] earlycon: Let users set the clock frequency

[PATCH v1 0/1] earlycon: Let users set the clock frequency

[Ricardo Ribalda]

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.

To: Jonathan Corbet <corbet@lwn.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

---
Ricardo Ribalda (1):
      earlycon: Let users set the clock frequency

 Documentation/admin-guide/kernel-parameters.txt | 12 +++++++-----
 drivers/tty/serial/earlycon.c                   |  7 ++++++-
 2 files changed, 13 insertions(+), 6 deletions(-)
---
base-commit: 4312098baf37ee17a8350725e6e0d0e8590252d4
change-id: 20221123-serial-clk-85db701ada57

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>

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

[Ricardo Ribalda]

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 <ribalda@chromium.org>

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

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

[Jiri Slaby]

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