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

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>

diff --git a/post/cpu/ppc4xx/uart.c b/post/cpu/ppc4xx/uart.c
index b047d42dfd303675f57a1dc5204b74b2a5b3a717..0aeed75ae6ff93a4142ec3e1dbfd59a397b6bad2 100644 (file)
--- a/post/cpu/ppc4xx/uart.c
+++ b/post/cpu/ppc4xx/uart.c
@@ -84,6 +84,49 @@
 
 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)
 {
        unsigned long reg;