0xFD000 is bdf 0/1f/5, not 0/1f/0

Is your SPI controller at function 5?    That’s where it usually is for Intel SoCs.

From: Rao G <grao.v80@gmail.com>
Sent: Friday, January 28, 2022 8:31 AM
To: coreboot <coreboot@coreboot.org>
Subject: [coreboot] SPIBAR + 0x10 offset with MMIOREAD32 causing exception

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Hi All,

Trying to access SPI Flash from EFI payload

1)

SpiInstance->PchSpiBase = MmPciBase (
                              DEFAULT_PCI_BUS_NUMBER_PCH,
                              PCI_DEVICE_NUMBER_PCH_SPI,
                              PCI_FUNCTION_NUMBER_PCH_SPI
                              );

DEBUG ((DEBUG_INFO, "PchSpiBase at 0x%x\n", SpiInstance->PchSpiBase));
>> returns PchSpiBase as 0xC00FD000 (Bus 0 Dev 1F Func 0)

2)

ScSpiBar0 = MmioRead32 (SpiInstance->PchSpiBase + PCI_BASE_ADDRESSREG_OFFSET) & 0xFFFFF000;

Expectation:

this should return value at 0xC00FD010

Result

The above code is throwing processor exception

PchSpiBase at 0xC00FD000
!!!! X64 Exception Type - 0E(#PF - Page-Fault)  CPU Apic ID - 00000000 !!!!
ExceptionData - 0000000000000000  I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
RIP  - 00000000771903D0, CS  - 0000000000000038, RFLAGS - 0000000000010046

Any clues whether SPI flash needs to be enabled in descriptor or any straps by using FIT tool?

Thanks

Rao