From: Ondrej Jirman megous@megous.com
Orange Pi 3 has 2 GiB of DRAM, that sometime get misdetected as 4 GiB, due to false negative result from mctl_mem_matches() when detecting number of column address bits. This leads to u-boot detecting more address bits than there are and the boot process hangs shortly after.
In mctl_mem_matches() we need to wait for each write to finish, separately. Without this, the check is not reliable for some unknown reason, probably having to do with unpredictable memory access ordering.
Patch was made with help from André Przywara, who noticed that my original idea about detection failing due to read-back from cache without involving DRAM was false, because data cache is still of at the time of the DRAM size autodetection.
Signed-off-by: Ondrej Jirman megous@megous.com Cc: André Przywara andre.przywara@arm.com --- arch/arm/mach-sunxi/dram_helpers.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm/mach-sunxi/dram_helpers.c b/arch/arm/mach-sunxi/dram_helpers.c index 239ab421a8..6dba448638 100644 --- a/arch/arm/mach-sunxi/dram_helpers.c +++ b/arch/arm/mach-sunxi/dram_helpers.c @@ -30,6 +30,7 @@ bool mctl_mem_matches(u32 offset) { /* Try to write different values to RAM at two addresses */ writel(0, CONFIG_SYS_SDRAM_BASE); + dsb(); writel(0xaa55aa55, (ulong)CONFIG_SYS_SDRAM_BASE + offset); dsb(); /* Check if the same value is actually observed when reading back */