AMD AGESA: How to access an indexed register?

[Paul Menzel]

Dear coreboot folks,

to read the value of the BIOS Timer (section 2.11.4 of the BIOS and
Kernel Developer’s Guide (BKDG) for the AMD Family 14 processors [1]), I
am stuck at how to do that.

Below is the register description from the BKDG.

D0F0xE4_x0130_80F0 BIOS Timer
        -----------------------------
        Reset: 0000_0000h.
        -----------------------------
        Bits
                31:0
        Description
                MicroSeconds. Read-write; updated-by hardware. This
                field increments once every microsecond when the timer
                is enabled. The counter rolls over and continues
                counting when it reaches FFFF_FFFFh. A write to this
                register causes the counter to reset and begin counting
                from the value written.

I could not find any wrapper(?) function in the non-vendor code for
that. In the vendor code directory `src/vendorcode/amd/agesa/f14/`, I
found only `PcieRegisterRead`, which looks “hard” to access from
outside.

$ git grep -i iocf8
        $ git grep -i d0f0xe4 src/vendorcode/amd/agesa/f14

Any pointers to code already dealing with such indexed registers or
instructions how to do that would help me very much.

Thanks,

Paul

[1] http://www.coreboot.org/Datasheets#AMD_Fam14
    BKDG 43170 Rev 3.13 – February 17, 2012

[Rudolf Marek]

Hi all,
> Any pointers to code already dealing with such indexed registers or
> instructions how to do that would help me very much.

Info is on page 150 of that datasheet.

D0F0xE0 and D0F0xE4 are used to access D0F0xE4_x[FFFF_FFFF:0000_0000]. To read 
or write to one of these register, the address is written first into the address 
register D0F0xE0 and then the data is read from or written to the data register 
D0F0xE4.

You can imagine that as a "window" to some internal address space (in this case 
address space of SMU)

You can even access that through a cmdline:

setpci -s 0:0.0 e0.l

This will print current register value of e0

So, to read the counter value:

setpci -s  0:0.0 e0.l=013080F0
setpci -s  0:0.0 e4.l

So, to read the default counter rate:

setpci -s  0:0.0 e0.l=013080F1
setpci -s  0:0.0 e4.l

Program it to any value:

setpci -s  0:0.0 e0.l=013080F0
setpci -s  0:0.0 e4.l=aa55aa55

To program the rate to 42 MHz

setpci -s  0:0.0 e0.l=013080F1
setpci -s  0:0.0 e4.l=0000002a

The setpci command is equivalent of this code:

setpci -s  0:0.0 e0.l=013080F0
setpci -s  0:0.0 e4.l

is:

pci_write_config32(CI_DEV(0, 0, 0), 0xe4, 0x013080F0);
tmp = pci_read_config32(PCI_DEV(0, 0, 0), 0xe4);

Happy hacking,
Rudolf