Re: [coreboot] Quick question on vt8237 smbus

[ron minnich]

On Mon, Oct 13, 2008 at 11:36 AM, Corey Osgood  wrote:
> I'm working on vt8237 smbus in v3, and I had a quick question, mostly for
> Rudolf Marek and Bari, but feel free to jump in with your 2 cents:
>
> u8 smbus_read_byte(u16 dimm, u8 offset, u16 smbus_io_base)
> {
>     u8 val;
> printk(BIOS_SPEW, "SMBus Read from DIMM %1x at address 0x%4x\n",
>             dimm, offset);
>
> smbus_reset(smbus_io_base);
>
> /* Clear host data port. */
> outb(0x00, smbus_io_base + SMBHSTDAT0);
> //SMBUS_DELAY();
> smbus_wait_until_ready(smbus_io_base);
>
> dimm = (dimm << 1) | 1;
>
> outb(dimm, smbus_io_base + SMBXMITADD);
>
> The dimm = (dimm << 1) | 1 is something that came from a via southbridge
> porting guide (NOT the one for the vt8237r, I don't have that one). With it,
> my spd addresses are 0x50, 0x51, etc, without it, they'd be 0xa1, 0xa3, etc.
> Which would be preferred? Do you think we'd ever need a 0xa0 or 0xa2
> address?

stick with 0x50 etc. The SMBUS address is the high 7 bits with opcode
in the lowest bit. So a1, a3, etc. are not real addresses. 50 and 51
are.

ron