[PATCH v2 2/4] PCI: brcmstb: Add ACPI config space quirk

[Jeremy Linton]

The PFTF CM4 is an ACPI platform that isn't ECAM compliant. Its config
space is in two parts. One part is for the root port registers and a
second moveable window pointing at a device's 4K config space. Thus it
doesn't have an MCFG, and any MCFG provided would be nonsense
anyway. Instead, a Linux specific host bridge _DSD selects a custom
ECAM ops and cfgres. The cfg op picks between those two regions while
disallowing problematic accesses.

Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
 drivers/pci/controller/Makefile            |  1 +
 drivers/pci/controller/pcie-brcmstb-acpi.c | 74 ++++++++++++++++++++++
 include/linux/pci-ecam.h                   |  1 +
 3 files changed, 76 insertions(+)
 create mode 100644 drivers/pci/controller/pcie-brcmstb-acpi.c

diff --git a/drivers/pci/controller/Makefile b/drivers/pci/controller/Makefile
index aaf30b3dcc14..65aa6fd3ed89 100644
--- a/drivers/pci/controller/Makefile
+++ b/drivers/pci/controller/Makefile
@@ -57,5 +57,6 @@ ifdef CONFIG_PCI_QUIRKS
 obj-$(CONFIG_ARM64) += pci-thunder-ecam.o
 obj-$(CONFIG_ARM64) += pci-thunder-pem.o
 obj-$(CONFIG_ARM64) += pci-xgene.o
+obj-$(CONFIG_ARM64) += pcie-brcmstb-acpi.o
 endif
 endif
diff --git a/drivers/pci/controller/pcie-brcmstb-acpi.c b/drivers/pci/controller/pcie-brcmstb-acpi.c
new file mode 100644
index 000000000000..71f6def3074c
--- /dev/null
+++ b/drivers/pci/controller/pcie-brcmstb-acpi.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ACPI quirks for Brcm2711 PCIe host controller
+ * As used on the Raspberry Pi Compute Module 4
+ *
+ * Copyright (C) 2021 Arm Ltd.
+ */
+
+#include <linux/io.h>
+#include <linux/pci.h>
+#include <linux/pci-ecam.h>
+#include "../pci.h"
+#include "pcie-brcmstb.h"
+
+static int brcm_acpi_init(struct pci_config_window *cfg)
+{
+	/*
+	 * This platform doesn't technically have anything that could be called
+	 * ECAM. Its config region has root port specific registers between
+	 * standard PCIe defined config registers. Thus the region setup by the
+	 * generic ECAM code needs to be adjusted. The HW can access bus 0-ff
+	 * but the footprint isn't a nice power of 2 (40k). For purposes of
+	 * mapping the config region we are just going to squash the standard
+	 * and nonstandard registers together rather than mapping them separately.
+	 */
+	iounmap(cfg->win);
+	cfg->win = pci_remap_cfgspace(cfg->res.start, resource_size(&cfg->res));
+	if (!cfg->win)
+		goto err_exit;
+
+	/* MSI is nonstandard as well */
+	pci_no_msi();
+
+	return 0;
+err_exit:
+	dev_err(cfg->parent, "PCI: Failed to remap config\n");
+	return -ENOMEM;
+}
+
+static void __iomem *brcm_pcie_map_conf2(struct pci_bus *bus,
+					unsigned int devfn, int where)
+{
+	struct pci_config_window *cfg = bus->sysdata;
+	void __iomem *base = cfg->win;
+	int idx;
+	u32 up;
+
+	/* Accesses to the RC go right to the RC registers if slot==0 */
+	if (pci_is_root_bus(bus))
+		return PCI_SLOT(devfn) ? NULL : base + where;
+
+	/* Assure link up before sending request */
+	up = readl(base + PCIE_MISC_PCIE_STATUS);
+	if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_DL_ACTIVE_MASK))
+		return NULL;
+
+	if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_PHYLINKUP_MASK))
+		return NULL;
+
+	/* For devices, write to the config space index register */
+	idx = PCIE_ECAM_OFFSET(bus->number, devfn, 0);
+	writel(idx, base + PCIE_EXT_CFG_INDEX);
+	return base + PCIE_EXT_CFG_DATA + where;
+}
+
+const struct pci_ecam_ops bcm2711_pcie_ops = {
+	.init		= brcm_acpi_init,
+	.bus_shift	= 1,
+	.pci_ops	= {
+		.map_bus	= brcm_pcie_map_conf2,
+		.read		= pci_generic_config_read,
+		.write		= pci_generic_config_write,
+	}
+};
diff --git a/include/linux/pci-ecam.h b/include/linux/pci-ecam.h
index adea5a4771cf..a5de0285bb7f 100644
--- a/include/linux/pci-ecam.h
+++ b/include/linux/pci-ecam.h
@@ -87,6 +87,7 @@ extern const struct pci_ecam_ops xgene_v1_pcie_ecam_ops; /* APM X-Gene PCIe v1 *
 extern const struct pci_ecam_ops xgene_v2_pcie_ecam_ops; /* APM X-Gene PCIe v2.x */
 extern const struct pci_ecam_ops al_pcie_ops;	/* Amazon Annapurna Labs PCIe */
 extern const struct pci_ecam_ops tegra194_pcie_ops; /* Tegra194 PCIe */
+extern const struct pci_ecam_ops bcm2711_pcie_ops; /* Bcm2711 PCIe */
 #endif
 
 #if IS_ENABLED(CONFIG_PCI_HOST_COMMON)
-- 
2.31.1