bios/sdram: check for optimal read window before doing read leveling, increment bitsl...

diff --git a/litex/soc/software/bios/sdram.c b/litex/soc/software/bios/sdram.c
index 5e694240f9a06057c6029d49221722bb4782eb37..b0e7416114f0824120962917ec3e118aecaf7e1d 100644 (file)
--- a/litex/soc/software/bios/sdram.c
+++ b/litex/soc/software/bios/sdram.c
@@ -336,6 +336,19 @@ static int write_level(int *delay, int *high_skew)
 
 #endif /* CSR_DDRPHY_WLEVEL_EN_ADDR */
 
+static void read_bitslip_inc(char m)
+{
+               ddrphy_dly_sel_write(1 << m);
+#ifdef KUSDDRPHY
+               ddrphy_rdly_dq_bitslip_write(1);
+#else
+               /* 7-series SERDES in DDR mode needs 3 pulses for 1 bitslip */
+               ddrphy_rdly_dq_bitslip_write(1);
+               ddrphy_rdly_dq_bitslip_write(1);
+               ddrphy_rdly_dq_bitslip_write(1);
+#endif
+}
+
 static void read_bitslip(int *delay, int *high_skew)
 {
        int bitslip_thr;
@@ -352,28 +365,22 @@ static void read_bitslip(int *delay, int *high_skew)
        printf("Read bitslip: ");
        for(i=DFII_PIX_DATA_SIZE/2-1;i>=0;i--)
                if(delay[i] > bitslip_thr) {
-                       ddrphy_dly_sel_write(1 << i);
-#ifdef KUSDDRPHY
-                       ddrphy_rdly_dq_bitslip_write(1);
-#else
-                       /* 7-series SERDES in DDR mode needs 3 pulses for 1 bitslip */
-                       ddrphy_rdly_dq_bitslip_write(1);
-                       ddrphy_rdly_dq_bitslip_write(1);
-                       ddrphy_rdly_dq_bitslip_write(1);
-#endif
+                       read_bitslip_inc(i);
                        printf("%d ", i);
                }
        printf("\n");
 }
 
-static void read_delays_scan(void)
+static int read_level_scan(int silent)
 {
        unsigned int prv;
        unsigned char prs[DFII_NPHASES*DFII_PIX_DATA_SIZE];
        int p, i, j;
        int working;
+       int optimal;
 
-       printf("Read delays scan:\n");
+       if (!silent)
+               printf("Read delays scan:\n");
 
        /* Generate pseudo-random sequence */
        prv = 42;
@@ -399,8 +406,10 @@ static void read_delays_scan(void)
        /* Calibrate each DQ in turn */
        sdram_dfii_pird_address_write(0);
        sdram_dfii_pird_baddress_write(0);
+       optimal = 1;
        for(i=DFII_PIX_DATA_SIZE/2-1;i>=0;i--) {
-               printf("m%d: ", (DFII_PIX_DATA_SIZE/2-i-1));
+               if (!silent)
+                       printf("m%d: ", (DFII_PIX_DATA_SIZE/2-i-1));
                ddrphy_dly_sel_write(1 << (DFII_PIX_DATA_SIZE/2-i-1));
                ddrphy_rdly_dq_rst_write(1);
                for(j=0; j<ERR_DDRPHY_DELAY;j++) {
@@ -413,10 +422,15 @@ static void read_delays_scan(void)
                                if(MMPTR(sdram_dfii_pix_rddata_addr[p]+4*(i+DFII_PIX_DATA_SIZE/2)) != prs[DFII_PIX_DATA_SIZE*p+i+DFII_PIX_DATA_SIZE/2])
                                        working = 0;
                        }
-                       printf("%d", working);
+                       if (j == 0)
+                               /* to have an optimal scan, first tap should not be working */
+                               optimal &= (working == 0);
+                       if (!silent)
+                               printf("%d", working);
                        ddrphy_rdly_dq_inc_write(1);
                }
-               printf("\n");
+               if (!silent)
+                       printf("\n");
        }
 
        /* Precharge */
@@ -424,9 +438,11 @@ static void read_delays_scan(void)
        sdram_dfii_pi0_baddress_write(0);
        command_p0(DFII_COMMAND_RAS|DFII_COMMAND_WE|DFII_COMMAND_CS);
        cdelay(15);
+
+       return optimal;
 }
 
-static void read_delays(void)
+static void read_level(void)
 {
        unsigned int prv;
        unsigned char prs[DFII_NPHASES*DFII_PIX_DATA_SIZE];
@@ -732,6 +748,7 @@ int sdrlevel(void) /* automatic */
 {
        int delay[DFII_PIX_DATA_SIZE/2];
        int high_skew[DFII_PIX_DATA_SIZE/2];
+       int i;
 
 #ifndef CSR_DDRPHY_WLEVEL_EN_ADDR
        int i;
@@ -744,9 +761,18 @@ int sdrlevel(void) /* automatic */
        if(!write_level(delay, high_skew))
                return 0;
 #endif
-       read_bitslip(delay, high_skew);
-       read_delays_scan();
-       read_delays();
+       /* check for optimal read leveling window */
+       if (read_level_scan(1)) {
+               /* if optimal, show scan */
+               read_level_scan(0);
+       } else {
+               /* else increment bitslip and re-scan */
+               printf("Read bitslip for optimal window\n");
+               for(i=0; i<DFII_PIX_DATA_SIZE/2; i++)
+                       read_bitslip_inc(i);
+               read_level_scan(0);
+       }
+       read_level();
 
        return 1;
 }