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

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Message-Id: <20210819215655.84866-3-jeremy.linton@arm.com>
Date:   Thu, 19 Aug 2021 16:56:53 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     linux-pci@...r.kernel.org
Cc:     lorenzo.pieralisi@....com, nsaenz@...nel.org, bhelgaas@...gle.com,
        rjw@...ysocki.net, lenb@...nel.org, robh@...nel.org, kw@...ux.com,
        f.fainelli@...il.com, sdonthineni@...dia.com,
        stefan.wahren@...e.com, bcm-kernel-feedback-list@...adcom.com,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jeremy Linton <jeremy.linton@....com>
Subject: [PATCH v2 2/4] PCI: brcmstb: Add ACPI config space quirk

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@....com>
---
 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