soc/amd/picasso: Add data fabric read helper function

Add new helper function to support reading a register from the data
fabric.

BUG=b:155307433
TEST=Boot trembyle with If64fd624597b2ced014ba7f0332a6a48143c0e8c and
confirm read values match expected values.
BRANCH=Zork

Change-Id: If0dc72063fbb99efaeea3fccef16cc1b5b8526f1
Signed-off-by: Jason Glenesk <jason.glenesk@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47726
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/picasso/data_fabric.c

@@ -167,3 +167,23 @@ static const struct pci_driver data_fabric_driver __pci_driver = {
 	.vendor			= PCI_VENDOR_ID_AMD,
 	.devices		= pci_device_ids,
 };
+
+uint32_t data_fabric_read_reg32(uint8_t function, uint16_t reg, uint8_t instance_id)
+{
+	uint32_t fabric_indirect_access_reg = 0;
+
+	if (instance_id == BROADCAST_FABRIC_ID)
+		/* No bit masking required. Macros will apply mask to values. */
+		return pci_read_config32(_SOC_DEV(DF_DEV, function), reg);
+
+	fabric_indirect_access_reg |= DF_IND_CFG_INST_ACC_EN;
+	/* Register offset field [10:2] in this register corresponds to [10:2] of the
+	   requested offset. */
+	fabric_indirect_access_reg |= reg & DF_IND_CFG_ACC_REG_MASK;
+	fabric_indirect_access_reg |=
+		(function << DF_IND_CFG_ACC_FUN_SHIFT) & DF_IND_CFG_ACC_FUN_MASK;
+	fabric_indirect_access_reg |= instance_id << DF_IND_CFG_INST_ID_SHIFT;
+	pci_write_config32(SOC_DF_F4_DEV, DF_FICAA_BIOS, fabric_indirect_access_reg);
+
+	return pci_read_config32(SOC_DF_F4_DEV, DF_FICAD_LO);
+}