On Monday 30 August 2021 11:10:55 Jeremy Linton wrote:

Hi,

On 8/29/21 6:13 AM, Pali Rohár wrote:

quoted

On Thursday 19 August 2021 16:56:53 Jeremy Linton wrote:

quoted

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.

I'm not sure if Lorenzo would like this patch series...

That was sorta true since the arm64/ACPI/PCI patches landed. The underlying
reason is the desire for arm platforms to require less one-off kernel
patching in order to "just work". But, its become apparent that there
continue to be problems with PCIe IP and Arm interconnect integration. So, a
firmware interface was standardized which solves most of the nonstandard
ECAM issues. At that point it was decided though that the kernel maintainers
would prefer to have the quirks visible to the kernel rather than hidden in
the firmware, and that they would be more open to merging these quirks. The
Tegra patch you listed above has been merged.

More info about this: https://lkml.org/lkml/2021/3/25/777

Hi and thanks for pointer!

I did not know about that new discussion and a new solution.

Anyway, according to that discussion, adding a new MCFG quirk into
kernel requires adding some errata entry for documenting buggy HW. And
seems that this documentation update is not included in this patch
series...

Thanks,

quoted

In past there was a long discussion about ECAM compliance, MCFG quirks
and usage of ACPI (on other platform), see long thread:
https://lore.kernel.org/linux-pci/20200207183427.GA40158@google.com/ (local)

And I think it is not a good idea to extend MCFG quirks table as
according to discussion it was just temporary plaster and if platform is
not ACPI / ECAM compliant then it should use DT booting...

Lorenzo, could you put any comment on this?

quoted

Signed-off-by: Jeremy Linton <redacted>
---
  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