This patch fixes the DDR3 initialization procedure in order to comply with DDR3 standard. A 500 us delay is specified between the DDR3 reset and clock enable signal. Until now, this delay was not respected. Some DDR3 chips don't bother but the bigger the RAM becomes the more likely it seems that this delay is needed. We observed that DRAM > 256 MB from the manufacturer Samsung have an issue when the specification is not respected.
Changes:
1) Add a 1 ms wait for L3 timeout error trigger
2) Don't delay DDR3 initialization Bit 31 of emif_sdram_ref_ctrl shouldn't be set because his suppresses the initialization of DDR3
Signed-off-by: Samuel Egli samuel.egli@siemens.com Reviewed-by: James Doublesin doublesin@ti.com Cc: Tom Rini trini@konsulko.com Cc: Felipe Balbi balbi@ti.com Cc: Roger Meier r.meier@siemens.com Cc: Heiko Schocher hs@denx.de --- arch/arm/cpu/armv7/am33xx/ddr.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/arm/cpu/armv7/am33xx/ddr.c b/arch/arm/cpu/armv7/am33xx/ddr.c index b3fb0c4..888cf1f 100644 --- a/arch/arm/cpu/armv7/am33xx/ddr.c +++ b/arch/arm/cpu/armv7/am33xx/ddr.c @@ -164,6 +164,13 @@ void config_sdram(const struct emif_regs *regs, int nr) writel(regs->zq_config, &emif_reg[nr]->emif_zq_config); writel(regs->sdram_config, &cstat->secure_emif_sdram_config); writel(regs->sdram_config, &emif_reg[nr]->emif_sdram_config); + + /* Trigger initialization */ + writel(0x00003100, &emif_reg[nr]->emif_sdram_ref_ctrl); + /* Wait 1ms because of L3 timeout error */ + udelay(1000); + + /* Write proper sdram_ref_cref_ctrl value */ writel(regs->ref_ctrl, &emif_reg[nr]->emif_sdram_ref_ctrl); writel(regs->ref_ctrl, &emif_reg[nr]->emif_sdram_ref_ctrl_shdw); } @@ -292,7 +299,9 @@ void config_ddr_phy(const struct emif_regs *regs, int nr) EMIF_REG_INITREF_DIS_MASK); #endif if (regs->zq_config) - writel(0x80003100, &emif_reg[nr]->emif_sdram_ref_ctrl); + /* Set time between rising edge of DDR_RESET to rising + * edge of DDR_CKE to > 500us per memory spec. */ + writel(0x00003100, &emif_reg[nr]->emif_sdram_ref_ctrl);
writel(regs->emif_ddr_phy_ctlr_1, &emif_reg[nr]->emif_ddr_phy_ctrl_1);