diff options
Diffstat (limited to 'cpu/mpc86xx/spd_sdram.c')
| -rw-r--r-- | cpu/mpc86xx/spd_sdram.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/cpu/mpc86xx/spd_sdram.c b/cpu/mpc86xx/spd_sdram.c index ac9ff81ce..f37ab430b 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; + /* use unsigned long long to avoid rounding errors */ + const unsigned long long ULL_2e12 = 2000000000000ULL; + unsigned long long clks; + unsigned long long clks_temp; - clks = picos / (2000000000 / (get_bus_freq(0) / 1000)); - if (picos % (2000000000 / (get_bus_freq(0) / 1000)) != 0) { + 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; } |