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bios/sdram: improve/simplify read window selection 

Compute a score for each window and select the best
This commit is contained in:
Florent Kermarrec 2018-08-22 23:15:32 +02:00
parent 09776b77e6
commit 759e7d4dc3
1 changed files with 28 additions and 28 deletions
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56
litex/soc/software/bios/sdram.c
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@ -377,9 +377,7 @@ 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 working_delays;
int optimal;
int score;
if (!silent)
printf("Read delays scan:\n");
@ -408,32 +406,26 @@ static int read_level_scan(int silent)
/* Calibrate each DQ in turn */
sdram_dfii_pird_address_write(0);
sdram_dfii_pird_baddress_write(0);
working = 0;
working_delays = 0;
optimal = 1;
score = 0;
for(i=DFII_PIX_DATA_SIZE/2-1;i>=0;i--) {
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++) {
int working_delay;
int working;
command_prd(DFII_COMMAND_CAS|DFII_COMMAND_CS|DFII_COMMAND_RDDATA);
cdelay(15);
working_delay = 1;
working = 1;
for(p=0;p<DFII_NPHASES;p++) {
if(MMPTR(sdram_dfii_pix_rddata_addr[p]+4*i) != prs[DFII_PIX_DATA_SIZE*p+i])
working_delay = 0;
working = 0;
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_delay = 0;
working = 0;
}
working |= working_delay;
working_delays += working_delay;
if ((j == 0) || (j == (ERR_DDRPHY_DELAY-1)))
/* to have an optimal scan, first tap and last tap should not be working */
optimal &= (working_delay == 0);
if (!silent)
printf("%d", working_delay);
printf("%d", working);
score += working;
ddrphy_rdly_dq_inc_write(1);
}
if (!silent)
@ -446,8 +438,7 @@ static int read_level_scan(int silent)
command_p0(DFII_COMMAND_RAS|DFII_COMMAND_WE|DFII_COMMAND_CS);
cdelay(15);
/* Successful if working and optimal or number of working delays > 3/4 of the taps */
return working & (optimal | working_delays > 3*(DFII_PIX_DATA_SIZE/2)*ERR_DDRPHY_DELAY/4);
return score;
}
static void read_level(void)
@ -732,6 +723,9 @@ int sdrlevel(void)
int high_skew[DFII_PIX_DATA_SIZE/2];
int i, j;
int bitslip;
int score;
int best_score;
int best_bitslip;
for(i=0; i<DFII_PIX_DATA_SIZE/2; i++) {
ddrphy_dly_sel_write(1<<i);
@ -749,29 +743,35 @@ int sdrlevel(void)
if(!write_level(delay, high_skew))
return 0;
#endif
/* check possible read windows (based on bitslip) */
/* scan possible read windows */
best_score = 0;
best_bitslip = 0;
for(bitslip=0; bitslip<ERR_DDRPHY_BITSLIP; bitslip++) {
/* scan */
if (read_level_scan(1))
break;
/* compute score */
score = read_level_scan(1);
if (score > best_score) {
best_bitslip = bitslip;
best_score = score;
}
/* exit */
if (bitslip == ERR_DDRPHY_BITSLIP-1)
return 0;
break;
/* increment bitslip */
for(i=0; i<DFII_PIX_DATA_SIZE/2; i++)
read_bitslip_inc(i);
}
/* select read window (bitslip)*/
printf("Read bitslip: %d\n", bitslip);
/* select best read window */
printf("Read bitslip: %d\n", best_bitslip);
for(i=0; i<DFII_PIX_DATA_SIZE/2; i++) {
ddrphy_dly_sel_write(1<<i);
ddrphy_rdly_dq_bitslip_rst_write(1);
for (j=0; j<bitslip; j++)
for (j=0; j<best_bitslip; j++)
read_bitslip_inc(i);
}
/* scan selected read window */
read_level_scan(0);
/* show scan and do leveling */
read_level_scan(0);
read_level();
return 1;