soc/intel/common/pcie: Add helper function for getting mask of enabled ports

This change adds a helper function `pcie_rp_enable_mask()` that
returns a 32-bit mask indicating the status (enabled/disabled) of PCIe
root ports (in the groups table) as configured by the mainboard in the
device tree.

With this helper function, SoC chip config does not need to add
another `PcieRpEnable[]` config to identify what root ports are
enabled.

Change-Id: I7ce5fca1c662064fd21f0961dac13cda1fa2ca44
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48968
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/block/include/intelblocks/pcie_rp.h

@@ -3,6 +3,8 @@
 #ifndef SOC_INTEL_COMMON_BLOCK_PCIE_RP_H
 #define SOC_INTEL_COMMON_BLOCK_PCIE_RP_H
 
+#include <stdint.h>
+
 /*
  * The PCIe Root Ports usually come in groups of up to 8 PCI-device
  * functions.
@@ -34,4 +36,17 @@ struct pcie_rp_group {
  */
 void pcie_rp_update_devicetree(const struct pcie_rp_group *groups);
 
+/*
+ * Return mask of PCIe root ports that are enabled by mainboard. Mask is set in the same order
+ * as the root ports in pcie_rp_group groups table.
+ *
+ * Thus, the status of first root port in the groups table is indicated by bit 0 in the returned
+ * mask, second root port by bit 1 and so on.
+
+ * 1 in the bit position indicates root port is enabled, whereas 0 indicates root port is
+ * disabled. This function assumes that the maximum count of root ports in the groups table is
+ * <= 32.
+ */
+uint32_t pcie_rp_enable_mask(const struct pcie_rp_group *groups);
+
 #endif /* SOC_INTEL_COMMON_BLOCK_PCIE_RP_H */

src/soc/intel/common/block/pcie/Makefile.inc

@@ -1,4 +1,7 @@
 subdirs-y += ./*
 
+romstage-$(CONFIG_SOC_INTEL_COMMON_BLOCK_PCIE) += pcie_helpers.c
+
 ramstage-$(CONFIG_SOC_INTEL_COMMON_BLOCK_PCIE) += pcie.c
+ramstage-$(CONFIG_SOC_INTEL_COMMON_BLOCK_PCIE) += pcie_helpers.c
 ramstage-$(CONFIG_SOC_INTEL_COMMON_BLOCK_PCIE) += pcie_rp.c

src/soc/intel/common/block/pcie/pcie_helpers.c

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/console.h>
+#include <device/device.h>
+#include <intelblocks/pcie_rp.h>
+#include <stdint.h>
+
+static uint32_t pcie_slot_enable_mask(unsigned int slot, unsigned int count)
+{
+	uint32_t mask = 0;
+	unsigned int i;
+	const struct device *dev;
+
+	for (i = 0; i < count; i++) {
+		dev = pcidev_on_root(slot, i);
+		if (is_dev_enabled(dev))
+			mask |= BIT(i);
+	}
+
+	return mask;
+}
+
+uint32_t pcie_rp_enable_mask(const struct pcie_rp_group *const groups)
+{
+	uint32_t mask = 0;
+	uint32_t offset = 0;
+	const struct pcie_rp_group *group;
+
+	for (group = groups; group->count; ++group) {
+		if (group->count + offset >= sizeof(mask) * 8) {
+			printk(BIOS_ERR, "ERROR: %s: Root port count greater than mask size!\n",
+			       __func__);
+			break;
+		}
+		mask |= pcie_slot_enable_mask(group->slot, group->count) << offset;
+		offset += group->count;
+	}
+
+	return mask;
+}