[U-Boot] PPC4XX Custom Board - Failing to read I2C

[txcotrader]

I feel like something "different" is happening when executing the io.h->out_8
function. Could somebody help me understand this op code 

v2013.01.01 Code:
extern inline void out_8(volatile unsigned char __iomem *addr, u8 val)
{
    __asm__ __volatile__("sync;\n"
                 "stb%U0%X0 %1,%0;\n"
                 : "=m" (*addr)
                 : "r" (val));
}


Old 1.7.02 Code:
extern inline void out_8(volatile unsigned char __iomem *addr, int val)
{
    __asm__ __volatile__("stb%U0%X0 %1,%0; eieio" : "=m" (*addr) : "r"
(val));
}

So I understand the sync op code but what is going on here? Could someone
with some expertise explain "stb%U0%X0 %1,%0" and "stb%U0%X0 %1,%0; eieio". 

Thanks!




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