Re: [PATCH v3 1/2] earlycon: Let users set the clock frequency

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On 24. 11. 22, 13:39, 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.

Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>

Reviewed-by: Jiri Slaby <jirislaby@xxxxxxxxxx>

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..3a0c88419b6c 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -120,7 +120,13 @@ 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 && kstrtouint(uartclk + 1, 0, &port->uartclk) < 0)
+			pr_warn("[%s] unsupported earlycon uart clkrate option\n",
+				options);
  		length = min(strcspn(options, " ") + 1,
  			     (size_t)(sizeof(device->options)));
  		strscpy(device->options, options, length);
@@ -139,7 +145,8 @@ 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);

--
js
suse labs




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