[Skiboot] [PATCH 3/5] libflash/mbox-flash: Update to V2 of the protocol

[Benjamin Herrenschmidt]

On Mon, 2017-04-24 at 19:14 +1000, Cyril Bur wrote:
> +       while(len) {
> +               uint32_t chunk;
> +               uint32_t dat;
> +
> +               /* XXX: make this read until it's aligned */
> +               if (len > 3 && !(off & 3)) {
> +                       rc = lpc_read(OPAL_LPC_FW, off, &dat, 4);
> +                       if (!rc)
> +                               *(uint32_t *)buf = dat;
> +                       chunk = 4;
> +               } else {
> +                       rc = lpc_read(OPAL_LPC_FW, off, &dat, 1);
> +                       if (!rc)
> +                               *(uint8_t *)buf = dat;
> +                       chunk = 1;
> +               }
> +               if (rc) {

You'll acquire/release a lock for every 4 bytes.. In HostBoot, I've
updated the underlying lpc_read to take arbitrary quantities instead
(though only on memory mapped LPC, ie, P9)..

To do that, I'd rework opb_mmio_write() and opb_mmio_read() along
the lines of:

	sync();
	while (size > 3 && !(offset & 3))
		__in/out_be32
	while (size > 1 && !(offset & 1))
		__in/out_be16
	while
(size)
		__in/out_8

That will provide correct semantics for all cases and limits the
amount of locks and sync's in bulk transfers which should speed
things up a bit.

Cheers,
Ben.