Re: [U-Boot] [PATCH] p1022ds: fix switching of DIU/LBC signals

...

 /* There is no __raw_writeq(), so do the write manually */
 *(volatile u64 *)addr = value;

• if (sw)

• if (sw) {

•        /*
  

•         * To ensure the post-write is completed to eLBC, software must
  

•         * perform a dummy read from one valid address from eLBC space
  

•         * before changing the eLBC_DIU from NOR mode to DIU mode.
  

•         */
  

•        __raw_readb(addr);
         set_mux_to_diu();
  

• }

Careful with the barriers.

You've got a raw readback, which means it's not going to wait for completion with the twi/isync hack.

Ordinarily that would be OK, since you only need ordering between the readb and the first access in set_mux_to_diu(). Unfortunately, that first access is an 8-bit access, which for some strange reason does sync differently than 16/32-bit accesses. The latter do sync+write, but 8-bit does write+eieio. So there's no barrier between the read and the write.

Any reason not to use in_8 here?

Timur, Any reason not to use in_be8? The first version code is finished by me some months ago. at that time I used the in_be8.

Thanks, Dave