Read-to-read/Write-to-write turnaround for same chip select
of DDR3 memory, BL/2+2 cycles is enough for them at BC4 and
OTF case, BL/2 cycles is enough for fixed BL8.
Cutting down the turnaround from BL/2+4 to BL/2+2 or BL/2
will improve the memory performance.
Signed-off-by: Dave Liu <dave...@freescale.com>
---
cpu/mpc8xxx/ddr/ctrl_regs.c | 17 ++++++++++++-----
1 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/cpu/mpc8xxx/ddr/ctrl_regs.c b/cpu/mpc8xxx/ddr/ctrl_regs.c
index 73f349f..aeb54c3 100644
--- a/cpu/mpc8xxx/ddr/ctrl_regs.c
+++ b/cpu/mpc8xxx/ddr/ctrl_regs.c
@@ -939,7 +939,8 @@ static void set_ddr_init_ext_addr(fsl_ddr_cfg_regs_t *ddr)
}
/* DDR SDRAM Timing Configuration 4 (TIMING_CFG_4) */
-static void set_timing_cfg_4(fsl_ddr_cfg_regs_t *ddr)
+static void set_timing_cfg_4(fsl_ddr_cfg_regs_t *ddr,
+ const memctl_options_t *popts)
{
unsigned int rwt = 0; /* Read-to-write turnaround for same CS */
unsigned int wrt = 0; /* Write-to-read turnaround for same CS */
@@ -948,9 +949,15 @@ static void set_timing_cfg_4(fsl_ddr_cfg_regs_t *ddr)
unsigned int dll_lock = 0; /* DDR SDRAM DLL Lock Time */
#if defined(CONFIG_FSL_DDR3)
- /* We need set BL/2 + 4 for BC4 or OTF */
- rrt = 4; /* BL/2 + 4 clocks */
- wwt = 4; /* BL/2 + 4 clocks */
+ if (popts->burst_length == DDR_BL8) {
+ /* We set BL/2 for fixed BL8 */
+ rrt = 0; /* BL/2 clocks */
+ wwt = 0; /* BL/2 clocks */
+ } else {
+ /* We need to set BL/2 + 2 to BC4 and OTF */
+ rrt = 2; /* BL/2 + 2 clocks */
+ wwt = 2; /* BL/2 + 2 clocks */
+ }
dll_lock = 1; /* tDLLK = 512 clocks from spec */
#endif
ddr->timing_cfg_4 = (0
@@ -1348,7 +1355,7 @@ compute_fsl_memctl_config_regs(const memctl_options_t
*popts,
set_ddr_sdram_clk_cntl(ddr, popts);
set_ddr_init_addr(ddr);
set_ddr_init_ext_addr(ddr);
- set_timing_cfg_4(ddr);
+ set_timing_cfg_4(ddr, popts);
set_timing_cfg_5(ddr);
set_ddr_zq_cntl(ddr, zq_en);
--
1.6.4
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