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authorJens Gehrlein <jens.gehrlein@tqs.de>2007-09-27 14:54:46 +0200
committerWolfgang Denk <wd@denx.de>2007-12-27 01:59:33 +0100
commit492c7049869348d31168de8dad89651315e468e0 (patch)
tree573286b141da27fd8ee66b0a15f2876dd56ce55c /include
parentdabad4b9bc46908e301f73ce76b38b23626a96e9 (diff)
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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>
Diffstat (limited to 'include')
-rw-r--r--include/configs/TQM885D.h36
1 files changed, 20 insertions, 16 deletions
diff --git a/include/configs/TQM885D.h b/include/configs/TQM885D.h
index f36b729..a8fbbfb 100644
--- a/include/configs/TQM885D.h
+++ b/include/configs/TQM885D.h
@@ -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