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| author | Martin Krause <martin.krause@tqs.de> | 2007-09-27 14:54:36 +0200 |
|---|---|---|
| committer | Martin Krause <martin.krause@tqs.de> | 2007-10-15 09:45:00 +0200 |
| commit | d43e489baf02afae49077791fb22332d240d8656 (patch) | |
| tree | 33df86abe51f3aeebb7580fdc197b4b626bbf054 /include/configs | |
| parent | 9ef57bbee1c67cc01da2026c242c4692db32be36 (diff) | |
| download | u-boot-imx-d43e489baf02afae49077791fb22332d240d8656.zip u-boot-imx-d43e489baf02afae49077791fb22332d240d8656.tar.gz u-boot-imx-d43e489baf02afae49077791fb22332d240d8656.tar.bz2 | |
TQM866M: fix SDRAM refresh
At 133 MHz the current SDRAM refresh rate is too fast
(measured 4 * 1.17 us).
CFG_MAMR_PTA changes from 39 to 97. This result
in a refresh rate of 4 * 7.8 us at the default clock
50 MHz. At 133 MHz the value will be then 4 * 2.9 us.
This is a compromise until a new method is found to
adjust the refresh rate.
Signed-off-by: Martin Krause <martin.krause@tqs.de>
Diffstat (limited to 'include/configs')
| -rw-r--r-- | include/configs/TQM866M.h | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/include/configs/TQM866M.h b/include/configs/TQM866M.h index 76facc4..ca3c166 100644 --- a/include/configs/TQM866M.h +++ b/include/configs/TQM866M.h @@ -426,26 +426,30 @@ #define CFG_PTA_PER_CLK ((4096 * 64 * 1000) / (4 * 64)) /* - * Memory Periodic Timer Prescaler - * Periodic timer for refresh, start with refresh rate for 40 MHz clock - * (CFG_8xx_CPUCLK_MIN / CFG_PTA_PER_CLK) + * Periodic timer (MAMR[PTx]) for 4 * 7.8 us refresh (= 31.2 us per quad) + * + * CPUclock(MHz) * 31.2 + * CFG_MAMR_PTA = ----------------------------------- with DFBRG = 0 + * 2^(2*SCCR[DFBRG]) * MPTPR_PTP_DIV16 + * + * CPU clock = 15 MHz: CFG_MAMR_PTA = 29 -> 4 * 7.73 us + * CPU clock = 50 MHz: CFG_MAMR_PTA = 97 -> 4 * 7.76 us + * CPU clock = 66 MHz: CFG_MAMR_PTA = 128 -> 4 * 7.75 us + * CPU clock = 133 MHz: CFG_MAMR_PTA = 255 -> 4 * 7.67 us + * + * Value 97 is for 4 * 7.8 us at 50 MHz. So the refresh cycle requirement will + * be met also in the default configuration, i.e. if environment variable + * 'cpuclk' is not set. */ -#define CFG_MAMR_PTA 39 +#define CFG_MAMR_PTA 97 /* - * For 16 MBit, refresh rates could be 31.3 us - * (= 64 ms / 2K = 125 / quad bursts). - * For a simpler initialization, 15.6 us is used instead. - * - * #define CFG_MPTPR_2BK_2K MPTPR_PTP_DIV32 for 2 banks - * #define CFG_MPTPR_1BK_2K MPTPR_PTP_DIV64 for 1 bank + * Memory Periodic Timer Prescaler Register (MPTPR) values. */ -#define CFG_MPTPR_2BK_4K MPTPR_PTP_DIV16 /* setting for 2 banks */ -#define CFG_MPTPR_1BK_4K MPTPR_PTP_DIV32 /* setting for 1 bank */ - -/* refresh rate 7.8 us (= 64 ms / 8K = 31.2 / quad bursts) for 256 MBit */ -#define CFG_MPTPR_2BK_8K MPTPR_PTP_DIV8 /* setting for 2 banks */ -#define CFG_MPTPR_1BK_8K MPTPR_PTP_DIV16 /* setting for 1 bank */ +/* 4 * 7.8 us refresh (= 31.2 us per quad) at 50 MHz and PTA = 97 */ +#define CFG_MPTPR_2BK_4K MPTPR_PTP_DIV16 +/* 4 * 3.9 us refresh (= 15.6 us per quad) at 50 MHz and PTA = 97 */ +#define CFG_MPTPR_2BK_8K MPTPR_PTP_DIV8 /* * MAMR settings for SDRAM |