[coreboot] v2[PATCH]RCA RM4100 i82830 support

[joe at smittys.pointclark.net]

Quoting Corey Osgood <corey.osgood at gmail.com>:

>
> On Tue, 2008-02-26 at 16:19 -0500, joe at smittys.pointclark.net wrote:
>> >> +static void do_ram_command(const struct mem_controller *ctrl,
>> >> uint32_t command, uint32_t addr_offset)
>> >> +{
>> >> <snip>
>> >> +
>> >> +	/* Read from (DIMM start address + addr_offset). */
>> >> +	read32(0 + addr_offset);	//first offset is always 0
>> >> +}
>> >
>> > This isn't ready for multiple dimms yet. See the cn700 patch I
>> > recently sent (but haven't committed yet, I think it was acked).
>> >
>> Oh you mean this? What do I need to do to adapt it for the i82830?
>>
>> +	/* NOTE: Dual-sided ready */
>>   	read32(0 + addr_offset);
>> +	for(i = 0; i < (ARRAY_SIZE(ctrl->channel0) * 2); i++) {
>> +		reg8 = pci_read_config8(ctrl->d0f3, 0x40 + i);
>> + 	if(reg8) read32((reg8 << 26) + addr_offset);
>> + }
>
> This reads from register 0x40 + i, where 0x40 is the top of the first
> dimm, and i counts to the max number of dimms.

Why read this from a register?? Why not just use (i = 0; i <  
DIMM_SOCKETS; i++)

> Reg 0x40 contains bits
> 33:26 of the top address, hence the << 26. So you'd need to adjust both
> of these to fit the i830's DRB mechanism. If the i830 uses an ugly
> format like the i810 does, then it may be easier to store the size in
> scratch registers somewhere after it's calculated, and then use those
> values instead. Sorry I can't get more specific, I've got to head out to
> my next service call.
>
The DRB i830 is not ugly it is very simple, simple, simple. So simple  
that it just calculates the memory size in ticks of 32 per side * the  
next side up to 4 sides. Like this:

Example: 128MB SINGLE sided so-dimm in slot 1
          128MB DOUBLE sided so-dimm in slot 2

There are 4 DRB registers(actually 6 but but only 4 that are usable -  
Intel design glitch), 1 for each side. So in this example they would  
look like this:

DRB1 = 0x04
DRB2 = 0x04
DRB3 = 0x06
DRB4 = 0x08

So if we needed to convert this we would do something like this (DRB *  
32) * 1024 correct? But if we just need to calculate the end of  
so-dimm #1 and the start of so-dimm #2 the only important register  
would be DRB2 (side 2 of so-dimm #1) and DRB3(side 1 of so-dimm #2),  
correct?

Thanks - Joe