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Diffstat (limited to 'arch/powerpc/kernel/udbg_16550.c')
-rw-r--r--arch/powerpc/kernel/udbg_16550.c63
1 files changed, 53 insertions, 10 deletions
diff --git a/arch/powerpc/kernel/udbg_16550.c b/arch/powerpc/kernel/udbg_16550.c
index 9313574ab935..50fd376446c9 100644
--- a/arch/powerpc/kernel/udbg_16550.c
+++ b/arch/powerpc/kernel/udbg_16550.c
@@ -43,6 +43,8 @@ struct NS16550 {
#define LSR_TEMT 0x40 /* Xmitter empty */
#define LSR_ERR 0x80 /* Error */
+#define LCR_DLAB 0x80
+
static volatile struct NS16550 __iomem *udbg_comport;
static void udbg_550_putc(unsigned char c)
@@ -77,29 +79,70 @@ static unsigned char udbg_550_getc(void)
return 0;
}
-void udbg_init_uart(void __iomem *comport, unsigned int speed)
+void udbg_init_uart(void __iomem *comport, unsigned int speed,
+ unsigned int clock)
{
- u16 dll = speed ? (115200 / speed) : 12;
+ unsigned int dll, base_bauds = clock / 16;
+
+ if (speed == 0)
+ speed = 9600;
+ dll = base_bauds / speed;
if (comport) {
udbg_comport = (struct NS16550 __iomem *)comport;
out_8(&udbg_comport->lcr, 0x00);
out_8(&udbg_comport->ier, 0xff);
out_8(&udbg_comport->ier, 0x00);
- out_8(&udbg_comport->lcr, 0x80); /* Access baud rate */
- out_8(&udbg_comport->dll, dll & 0xff); /* 1 = 115200, 2 = 57600,
- 3 = 38400, 12 = 9600 baud */
- out_8(&udbg_comport->dlm, dll >> 8); /* dll >> 8 which should be zero
- for fast rates; */
- out_8(&udbg_comport->lcr, 0x03); /* 8 data, 1 stop, no parity */
- out_8(&udbg_comport->mcr, 0x03); /* RTS/DTR */
- out_8(&udbg_comport->fcr ,0x07); /* Clear & enable FIFOs */
+ out_8(&udbg_comport->lcr, LCR_DLAB);
+ out_8(&udbg_comport->dll, dll & 0xff);
+ out_8(&udbg_comport->dlm, dll >> 8);
+ /* 8 data, 1 stop, no parity */
+ out_8(&udbg_comport->lcr, 0x03);
+ /* RTS/DTR */
+ out_8(&udbg_comport->mcr, 0x03);
+ /* Clear & enable FIFOs */
+ out_8(&udbg_comport->fcr ,0x07);
udbg_putc = udbg_550_putc;
udbg_getc = udbg_550_getc;
udbg_getc_poll = udbg_550_getc_poll;
}
}
+unsigned int udbg_probe_uart_speed(void __iomem *comport, unsigned int clock)
+{
+ unsigned int dll, dlm, divisor, prescaler, speed;
+ u8 old_lcr;
+ volatile struct NS16550 __iomem *port = comport;
+
+ old_lcr = in_8(&port->lcr);
+
+ /* select divisor latch registers. */
+ out_8(&port->lcr, LCR_DLAB);
+
+ /* now, read the divisor */
+ dll = in_8(&port->dll);
+ dlm = in_8(&port->dlm);
+ divisor = dlm << 8 | dll;
+
+ /* check prescaling */
+ if (in_8(&port->mcr) & 0x80)
+ prescaler = 4;
+ else
+ prescaler = 1;
+
+ /* restore the LCR */
+ out_8(&port->lcr, old_lcr);
+
+ /* calculate speed */
+ speed = (clock / prescaler) / (divisor * 16);
+
+ /* sanity check */
+ if (speed < 9600 || speed > 115200)
+ speed = 9600;
+
+ return speed;
+}
+
#ifdef CONFIG_PPC_MAPLE
void udbg_maple_real_putc(unsigned char c)
{