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Diffstat (limited to 'cpu/mpc86xx/spd_sdram.c')
-rw-r--r--cpu/mpc86xx/spd_sdram.c28
1 files changed, 20 insertions, 8 deletions
diff --git a/cpu/mpc86xx/spd_sdram.c b/cpu/mpc86xx/spd_sdram.c
index ac9ff81ce6..f37ab430b3 100644
--- a/cpu/mpc86xx/spd_sdram.c
+++ b/cpu/mpc86xx/spd_sdram.c
@@ -51,20 +51,32 @@ extern int dma_xfer(void *dest, uint count, void *src);
#define CFG_SUPER_BANK_INTERLEAVING 0
/*
- * Convert picoseconds into clock cycles (rounding up if needed).
+ * Convert picoseconds into DRAM clock cycles (rounding up if needed).
*/
-int
-picos_to_clk(int picos)
+static unsigned int
+picos_to_clk(unsigned int picos)
{
- int clks;
-
- clks = picos / (2000000000 / (get_bus_freq(0) / 1000));
- if (picos % (2000000000 / (get_bus_freq(0) / 1000)) != 0) {
+ /* use unsigned long long to avoid rounding errors */
+ const unsigned long long ULL_2e12 = 2000000000000ULL;
+ unsigned long long clks;
+ unsigned long long clks_temp;
+
+ if (! picos)
+ return 0;
+
+ clks = get_bus_freq(0) * (unsigned long long) picos;
+ clks_temp = clks;
+ clks = clks / ULL_2e12;
+ if (clks_temp % ULL_2e12) {
clks++;
}
- return clks;
+ if (clks > 0xFFFFFFFFULL) {
+ clks = 0xFFFFFFFFULL;
+ }
+
+ return (unsigned int) clks;
}