It's better to restore previous value at offset because otherwise the function can corrupt memory reserved by Linux (e.g. ramoops).
Signed-off-by: Andrei Lalaev andrei.lalaev@emlid.com --- arch/arm/mach-sunxi/dram_helpers.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/arm/mach-sunxi/dram_helpers.c b/arch/arm/mach-sunxi/dram_helpers.c index 2c873192e6..ed6db14f3c 100644 --- a/arch/arm/mach-sunxi/dram_helpers.c +++ b/arch/arm/mach-sunxi/dram_helpers.c @@ -32,12 +32,20 @@ void mctl_await_completion(u32 *reg, u32 mask, u32 val) #ifndef CONFIG_MACH_SUNIV bool mctl_mem_matches(u32 offset) { + ulong addr = CONFIG_SYS_SDRAM_BASE + offset; + u32 prev_val = readl(addr); + bool ret = false; + /* Try to write different values to RAM at two addresses */ writel(0, CONFIG_SYS_SDRAM_BASE); - writel(0xaa55aa55, (ulong)CONFIG_SYS_SDRAM_BASE + offset); + writel(0xaa55aa55, addr); dsb(); /* Check if the same value is actually observed when reading back */ - return readl(CONFIG_SYS_SDRAM_BASE) == - readl((ulong)CONFIG_SYS_SDRAM_BASE + offset); + ret = readl(CONFIG_SYS_SDRAM_BASE) == readl(addr); + + /* Restore previous value */ + writel(prev_val, addr); + + return ret; } #endif