[PATCH] earlycon: 8250: Fix command line regression

Peter Hurley
2015-04-03T23:04:11Z

Restore undocumented behavior of kernel command line parameters of
the forms:
console=uart[####],io|mmio|mmio32,<addr>[,options]
console=uart[####],<addr>[,options]
where 'options' have not been specified; in this case, the hardware
is assumed to be initialized.

Document the required behavior of the original implementation.

Reported-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
Documentation/kernel-parameters.txt | 15 +++++++++++----
drivers/tty/serial/8250/8250_core.c | 15 ++++++++++++++-
drivers/tty/serial/8250/8250_early.c | 19 -------------------
3 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a6..59c9832 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -711,12 +711,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Documentation/networking/netconsole.txt for an
alternative.

- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
+ uart[<n>],io,<addr>[,options]
+ uart[<n>],mmio,<addr>[,options]
+ uart[<n>],mmio32,<addr>[,options]
+ uart[<n>],0x<addr>[,options]
Start an early, polled-mode console on the 8250/16550
UART at the specified I/O port or MMIO address,
- switching to the matching ttyS device later. The
- options are the same as for ttyS, above.
+ switching to the matching ttyS device later.
+ Any optional number <n> is accepted and ignored.
+ If none of [io|mmio|mmio32], <addr> is assumed to be
+ equivalent to 'mmio'. 'options' are specified in the
+ same format described for ttyS above; if unspecified,
+ the h/w is not re-initialized.
+
hvc<n> Use the hypervisor console device <n>. This is for
both Xen and PowerPC hypervisors.

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e0fb5f0..5f41a9c 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -3456,12 +3456,17 @@ static int univ8250_console_setup(struct console *co, char *options)
*
* Only attempts to match console command lines of the form:
* console=uart<>,io|mmio|mmio32,<addr>,<options>
- * console=uart<>,<addr>,options
+ * console=uart<>,0x<addr>,<options>
* This form is used to register an initial earlycon boot console and
* replace it with the serial8250_console at 8250 driver init.
*
* Performs console setup for a match (as required by interface)
*
+ * ** HACK ALERT **
+ * If no <options> are specified, then assume the h/w is already setup.
+ * This was the undocumented behavior of the original implementation so
+ * it is cast in stone forever.
+ *
* Returns 0 if console matches; otherwise non-zero to use default matching
*/
static int univ8250_console_match(struct console *co, char *name, int idx,
@@ -3491,6 +3496,14 @@ static int univ8250_console_match(struct console *co, char *name, int idx,
continue;

co->index = i;
+
+ /* if no line settings, then assume h/w was setup */
+ if (!options) {
+ /* link port to console */
+ port->cons = co;
+ return 0;
+ }
+
return univ8250_console_setup(co, options);
}

diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index e95ebfe..8e11968 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -105,21 +105,6 @@ static void __init early_serial8250_write(struct console *console,
serial8250_early_out(port, UART_IER, ier);
}

-static unsigned int __init probe_baud(struct uart_port *port)
-{
- unsigned char lcr, dll, dlm;
- unsigned int quot;
-
- lcr = serial8250_early_in(port, UART_LCR);
- serial8250_early_out(port, UART_LCR, lcr | UART_LCR_DLAB);
- dll = serial8250_early_in(port, UART_DLL);
- dlm = serial8250_early_in(port, UART_DLM);
- serial8250_early_out(port, UART_LCR, lcr);
-
- quot = (dlm << 8) | dll;
- return (port->uartclk / 16) / quot;
-}
-
static void __init init_port(struct earlycon_device *device)
{
struct uart_port *port = &device->port;
@@ -151,10 +136,6 @@ static int __init early_serial8250_setup(struct earlycon_device *device,
struct uart_port *port = &device->port;
unsigned int ier;

- device->baud = probe_baud(&device->port);
- snprintf(device->options, sizeof(device->options), "%u",
- device->baud);
-
/* assume the device was initialized, only mask interrupts */
ier = serial8250_early_in(port, UART_IER);
serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
--
2.3.5