Re: [coreboot] Quick question on vt8237 smbus

[Marc Jones]

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?

My 2cents.
I have never really cared for the <<1. I prefer the more normal IO 
address. Most platform specs I have seen indicate the spd device at 
0xA0, 0xA2, etc.

Marc