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TQM885D: 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 128. This result
in a refresh rate of 4 * 7.8 us at the default clock
66 MHz. At 133 MHz the value will be then 4 * 3.8 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>
This commit is contained in:
Jens Gehrlein 2007-09-27 14:54:46 +02:00 committed by Wolfgang Denk
parent dabad4b9bc
commit 492c704986
1 changed files with 20 additions and 16 deletions
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36
include/configs/TQM885D.h
View File

@ -434,26 +434,30 @@
#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 128
/*
* 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