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POST: Add ppc4xx UART POST support without external uart clock (lwmon5)

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The patch adds support for UART POST on ppc44x-based boards with no
external serial clocks installed.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Acked-by: Stefan Roese <sr@denx.de>
This commit is contained in:
Yuri Tikhonov 2007-08-10 08:25:22 +02:00 • committed by Stefan Roese
parent 537223afa6
commit 29cb25da56
1 changed files with 43 additions and 0 deletions
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43
post/cpu/ppc4xx/uart.c
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@ -84,6 +84,49 @@
DECLARE_GLOBAL_DATA_PTR; DECLARE_GLOBAL_DATA_PTR;
#if !defined(CFG_EXT_SERIAL_CLOCK)
static void serial_divs (int baudrate, unsigned long *pudiv,
unsigned short *pbdiv)
{
sys_info_t sysinfo;
unsigned long div; /* total divisor udiv * bdiv */
unsigned long umin; /* minimum udiv */
unsigned short diff; /* smallest diff */
unsigned long udiv; /* best udiv */
unsigned short idiff; /* current diff */
unsigned short ibdiv; /* current bdiv */
unsigned long i;
unsigned long est; /* current estimate */
get_sys_info(&sysinfo);
udiv = 32; /* Assume lowest possible serial clk */
div = sysinfo.freqPLB / (16 * baudrate); /* total divisor */
umin = sysinfo.pllOpbDiv << 1; /* 2 x OPB divisor */
diff = 32; /* highest possible */
/* i is the test udiv value -- start with the largest
* possible (32) to minimize serial clock and constrain
* search to umin.
*/
for (i = 32; i > umin; i--) {
ibdiv = div / i;
est = i * ibdiv;
idiff = (est > div) ? (est-div) : (div-est);
if (idiff == 0) {
udiv = i;
break; /* can't do better */
} else if (idiff < diff) {
udiv = i; /* best so far */
diff = idiff; /* update lowest diff*/
}
}
*pudiv = udiv;
*pbdiv = div / udiv;
}
#endif
static int uart_post_init (unsigned long dev_base) static int uart_post_init (unsigned long dev_base)
{ {
unsigned long reg; unsigned long reg;