[RFC v2 2/4] ACPI: SPCR: don't initialize baud rate

[Aleksey Makarov]

AppliedMicro X-Gene based boards don't use the "standard"
16550 clock rate so supplying a baud rate makes it change
to a random baud rate.

I suggest to introduce a new value '0' for the "Baud
Rate" field of SPCR (now this value is reserved).

This patch introduces a check for this value.  In this case
the code does not emit baud rate specification for initialization
of the console.

Signed-off-by: Aleksey Makarov <aleksey.maka...@linaro.org>
---
 drivers/acpi/spcr.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 6c6710b..2bf338c 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -37,7 +37,7 @@ int __init parse_spcr(bool earlycon)
        acpi_status status;
        char *uart;
        char *iotype;
-       int baud_rate;
+       char *baud_rate_string;
        int err;
 
        if (acpi_disabled)
@@ -82,25 +82,33 @@ int __init parse_spcr(bool earlycon)
        }
 
        switch (table->baud_rate) {
+       case 0:
+               /*
+                * This value is not standaritzed by ACPI SPCR for now.
+                * It means that hardware should not be re-initialized with
+                * new speed.
+                */
+               baud_rate_string = "";
+               break;
        case 3:
-               baud_rate = 9600;
+               baud_rate_string = ",9600";
                break;
        case 4:
-               baud_rate = 19200;
+               baud_rate_string = ",19200";
                break;
        case 6:
-               baud_rate = 57600;
+               baud_rate_string = ",57600";
                break;
        case 7:
-               baud_rate = 115200;
+               baud_rate_string = ",115200";
                break;
        default:
                err = -ENOENT;
                goto done;
        }
 
-       snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
-                table->serial_port.address, baud_rate);
+       snprintf(opts, sizeof(opts), "%s,%s,0x%llx%s", uart, iotype,
+                table->serial_port.address, baud_rate_string);
 
        pr_info("console: %s\n", opts);
 
-- 
2.10.2