bios/sdram: make read leveling robust for KUS SDRAM

Increases the initial delay step into the valid read window as
with the original delay I was not getting out of the noisy
transition window, as evidenced by seeing read delay windows
of only 8 LSB ~10% of the time, leading to failing memory
tests

diff --git a/litex/soc/software/bios/sdram.c b/litex/soc/software/bios/sdram.c
index d9e3023d03e0383c2624d52d8fcdfe21365f6788..5b1ebd70125ff496cf7a56c551dc1e16552f710e 100644 (file)
--- a/litex/soc/software/bios/sdram.c
+++ b/litex/soc/software/bios/sdram.c
@@ -383,7 +383,7 @@ static void read_delays(void)
 
                /* Get a bit further into the working zone */
 #ifdef KUSDDRPHY
-               for(j=0;j<8;j++) {
+               for(j=0;j<16;j++) {
                        delay += 1;
                        ddrphy_rdly_dq_inc_write(1);
                }