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

Jeremy Linton
2021-08-19T21:57:21Z

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@arm.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