mpc512x: Adjust the DRAM init sequence to the datasheet spec

Do maintain a 200 usecs period of stable power and clock before
asserting the CKE signal and sending commands, have at least 200
DRAM clock cycles pass after initialization before data access.

Signed-off-by: Anatolij Gustschin <agust@denx.de>

diff --git a/arch/powerpc/cpu/mpc512x/fixed_sdram.c b/arch/powerpc/cpu/mpc512x/fixed_sdram.c
index 550cbd0bd6fcf1484e1c88158ceed156d25c0fff..6635fb036e8aa9c6d8d6f3107f7241bb8275413d 100644 (file)
--- a/arch/powerpc/cpu/mpc512x/fixed_sdram.c
+++ b/arch/powerpc/cpu/mpc512x/fixed_sdram.c
@@ -99,7 +99,19 @@ long int fixed_sdram(ddr512x_config_t *mddrc_config,
        sync_law(&im->sysconf.ddrlaw.ar);
 
        /* DDR Enable */
-       out_be32(&im->mddrc.ddr_sys_config, MDDRC_SYS_CFG_EN);
+       /*
+        * the "enable" combination: DRAM controller out of reset,
+        * clock enabled, command mode -- BUT leave CKE low for now
+        */
+       i = MDDRC_SYS_CFG_EN & ~MDDRC_SYS_CFG_CKE_MASK;
+       out_be32(&im->mddrc.ddr_sys_config, i);
+       /* maintain 200 microseconds of stable power and clock */
+       udelay(200);
+       /* apply a NOP, it shouldn't harm */
+       out_be32(&im->mddrc.ddr_command, CONFIG_SYS_DDRCMD_NOP);
+       /* now assert CKE (high) */
+       i |= MDDRC_SYS_CFG_CKE_MASK;
+       out_be32(&im->mddrc.ddr_sys_config, i);
 
        /* Initialize DDR Priority Manager */
        out_be32(&im->mddrc.prioman_config1, CONFIG_SYS_MDDRCGRP_PM_CFG1);
@@ -148,6 +160,9 @@ long int fixed_sdram(ddr512x_config_t *mddrc_config,
        out_be32(&im->mddrc.ddr_time_config0, mddrc_config->ddr_time_config0);
        out_be32(&im->mddrc.ddr_sys_config, mddrc_config->ddr_sys_config);
 
+       /* Allow for the DLL to startup before accessing data */
+       udelay(10);
+
        msize = get_ram_size(CONFIG_SYS_DDR_BASE, CONFIG_SYS_MAX_RAM_SIZE);
        /* Fix DDR Local Window for new size */
        out_be32(&im->sysconf.ddrlaw.ar, __ilog2(msize) - 1);

diff --git a/arch/powerpc/include/asm/immap_512x.h b/arch/powerpc/include/asm/immap_512x.h
index a330ad6df8453c34688949aa13ea1982d9266971..d96e53646ad88cff9a00bdadad9f71d5331610a1 100644 (file)
--- a/arch/powerpc/include/asm/immap_512x.h
+++ b/arch/powerpc/include/asm/immap_512x.h
@@ -351,6 +351,7 @@ typedef struct ddr512x {
 
 /* MDDRC SYS CFG and Timing CFG0 Registers */
 #define MDDRC_SYS_CFG_EN       0xF0000000
+#define MDDRC_SYS_CFG_CKE_MASK 0x40000000
 #define MDDRC_SYS_CFG_CMD_MASK 0x10000000
 #define MDDRC_REFRESH_ZERO_MASK        0x0000FFFF