__sst_read
#define sst_read(reg) __sst_read(par->mmio_vbase, reg)
__sst_write(vbase, reg, __sst_read(vbase, reg) | val);
__sst_write(vbase, reg, __sst_read(vbase, reg) & ~val);
if (__sst_read(vbase, STATUS) & STATUS_FBI_BUSY) {
ret = __sst_read(vbase, DAC_READ) & 0xff;