[PATCH V14 0/7] PCI: Loongson pci improvements and quirks

[PATCH V14 0/7] PCI: Loongson pci improvements and quirks

[Huacai Chen]

This patchset improves Loongson PCI controller driver and resolves some
problems: LS2K/LS7A's PCI config space supports 1/2/4-bytes access, so
the first patch use pci_generic_config_read()/pci_generic_config_write()
for them; the second patch add ACPI init support which will be used by
LoongArch; the third patch improves the mrrs quirk for LS7A chipset; The
fourth patch add a new quirk for LS7A chipset to avoid poweroff/reboot
failure, and the fifth patch add a new quirk for LS7A chipset to fix the
multifunction devices' irq pin mappings.

V1 -> V2:
1, Rework the 4th patch;
2, Improve commit messages;
3, Remove the last patch since there is better solutions.

V2 -> V3:
1, Add more affected device ids for the 4th patch;
2, Improve commit messages to describe root causes.

V3 -> V4:
1, Rework the MRRS quirk patch;
2, Improve commit messages to describe root causes, again.

V4 -> V5:
1, Improve the MRRS quirk patch;
2, Change the order of 2nd and 3rd patch;
3, Improve commit messages to describe root causes, again.

V5 -> V6:
1, Rework the 1st patch;
2, Adjust the order of the series.

V6 -> V7:
1, Use correct pci config access operations;
2, Add ACPI init support for LoongArch;
3, Don't move to quirks.c since the driver has ACPI support;
4, Some other minor improvements.

V7 -> V8:
1, Use CFG1 method for LS2K/LS7A pci config.

V8 -> V9:
1, Use pci_controller_data for the first patch. 

V9 -> V10:
1, Add a patch to avoid LS2K/LS7A access unexisting devices.

V10 -> V11:
1, Rebased on 5.16-rc4.

V11 -> V12:
1, Rebased on 5.17-rc5.

V12 -> V13:
1, Rebased on 5.18-rc2;
2, Some minor improvements (adopt Rob Herring's suggestions).

V13 -> V14:
1, Rebased on 5.18;
2, Split ARM64-specific mcfg_quirks to a separate patch;
3, Refactor "PCI: loongson: Don't access non-existant devices";
4, Refactor "PCI: Add quirk for LS7A to avoid reboot failure";
5, Some other minor improvements (adopt Bjorn's suggestions).

Huacai Chen, Tiezhu Yang and Jianmin Lv(6):
 PCI/ACPI: Guard ARM64-specific mcfg_quirks
 PCI: loongson: Use generic 8/16/32-bit config ops on LS2K/LS7A.
 PCI: loongson: Add ACPI init support.
 PCI: loongson: Don't access non-existant devices.
 PCI: loongson: Improve the MRRS quirk for LS7A.
 PCI: Add quirk for LS7A to avoid reboot failure.
 PCI: Add quirk for multifunction devices of LS7A.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn> 
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 drivers/acpi/pci_mcfg.c               |  13 ++
 drivers/pci/controller/Kconfig        |   2 +-
 drivers/pci/controller/pci-loongson.c | 233 ++++++++++++++++++++++++++--------
 drivers/pci/pci.c                     |   6 +
 drivers/pci/pcie/portdrv_core.c       |   1 -
 drivers/pci/pcie/portdrv_pci.c        |  20 ++-
 include/linux/pci-ecam.h              |   1 +
 include/linux/pci.h                   |   2 +
 8 files changed, 225 insertions(+), 53 deletions(-)
--
2.27.0

[PATCH V14 1/7] PCI/ACPI: Guard ARM64-specific mcfg_quirks

[Huacai Chen]

Guard ARM64-specific quirks with CONFIG_ARM64 to avoid build errors,
since mcfg_quirks will be shared by more than one architectures.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/acpi/pci_mcfg.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
index 53cab975f612..63b98eae5e75 100644
--- a/drivers/acpi/pci_mcfg.c
+++ b/drivers/acpi/pci_mcfg.c
@@ -41,6 +41,8 @@ struct mcfg_fixup {
 static struct mcfg_fixup mcfg_quirks[] = {
 /*	{ OEM_ID, OEM_TABLE_ID, REV, SEGMENT, BUS_RANGE, ops, cfgres }, */
 
+#ifdef CONFIG_ARM64
+
 #define AL_ECAM(table_id, rev, seg, ops) \
 	{ "AMAZON", table_id, rev, seg, MCFG_BUS_ANY, ops }
 
@@ -169,6 +171,7 @@ static struct mcfg_fixup mcfg_quirks[] = {
 	ALTRA_ECAM_QUIRK(1, 13),
 	ALTRA_ECAM_QUIRK(1, 14),
 	ALTRA_ECAM_QUIRK(1, 15),
+#endif /* ARM64 */
 };
 
 static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
-- 
2.27.0

[PATCH V14 2/7] PCI: loongson: Use generic 8/16/32-bit config ops on LS2K/LS7A

[Huacai Chen]

LS2K/LS7A support 8/16/32-bits PCI config access operations via CFG1, so
we can disable CFG0 for them and safely use pci_generic_config_read()/
pci_generic_config_write() instead of pci_generic_config_read32()/pci_
generic_config_write32().

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 65 +++++++++++++++++++--------
 1 file changed, 46 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 50a8e1d6f70a..565453882ffe 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -25,11 +25,16 @@
 #define FLAG_CFG1	BIT(1)
 #define FLAG_DEV_FIX	BIT(2)
 
+struct loongson_pci_data {
+	u32 flags;
+	struct pci_ops *ops;
+};
+
 struct loongson_pci {
 	void __iomem *cfg0_base;
 	void __iomem *cfg1_base;
 	struct platform_device *pdev;
-	u32 flags;
+	const struct loongson_pci_data *data;
 };
 
 /* Fixup wrong class code in PCIe bridges */
@@ -126,8 +131,8 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
 	 * Do not read more than one device on the bus other than
 	 * the host bus. For our hardware the root bus is always bus 0.
 	 */
-	if (priv->flags & FLAG_DEV_FIX && busnum != 0 &&
-		PCI_SLOT(devfn) > 0)
+	if (priv->data->flags & FLAG_DEV_FIX &&
+			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
 		return NULL;
 
 	/* CFG0 can only access standard space */
@@ -159,20 +164,42 @@ static int loongson_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 	return val;
 }
 
-/* H/w only accept 32-bit PCI operations */
+/* LS2K/LS7A accept 8/16/32-bit PCI config operations */
 static struct pci_ops loongson_pci_ops = {
+	.map_bus = pci_loongson_map_bus,
+	.read	= pci_generic_config_read,
+	.write	= pci_generic_config_write,
+};
+
+/* RS780/SR5690 only accept 32-bit PCI config operations */
+static struct pci_ops loongson_pci_ops32 = {
 	.map_bus = pci_loongson_map_bus,
 	.read	= pci_generic_config_read32,
 	.write	= pci_generic_config_write32,
 };
 
+static const struct loongson_pci_data ls2k_pci_data = {
+	.flags = FLAG_CFG1 | FLAG_DEV_FIX,
+	.ops = &loongson_pci_ops,
+};
+
+static const struct loongson_pci_data ls7a_pci_data = {
+	.flags = FLAG_CFG1 | FLAG_DEV_FIX,
+	.ops = &loongson_pci_ops,
+};
+
+static const struct loongson_pci_data rs780e_pci_data = {
+	.flags = FLAG_CFG0,
+	.ops = &loongson_pci_ops32,
+};
+
 static const struct of_device_id loongson_pci_of_match[] = {
 	{ .compatible = "loongson,ls2k-pci",
-		.data = (void *)(FLAG_CFG0 | FLAG_CFG1 | FLAG_DEV_FIX), },
+		.data = &ls2k_pci_data, },
 	{ .compatible = "loongson,ls7a-pci",
-		.data = (void *)(FLAG_CFG0 | FLAG_CFG1 | FLAG_DEV_FIX), },
+		.data = &ls7a_pci_data, },
 	{ .compatible = "loongson,rs780e-pci",
-		.data = (void *)(FLAG_CFG0), },
+		.data = &rs780e_pci_data, },
 	{}
 };
 
@@ -193,20 +220,20 @@ static int loongson_pci_probe(struct platform_device *pdev)
 
 	priv = pci_host_bridge_priv(bridge);
 	priv->pdev = pdev;
-	priv->flags = (unsigned long)of_device_get_match_data(dev);
+	priv->data = of_device_get_match_data(dev);
 
-	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!regs) {
-		dev_err(dev, "missing mem resources for cfg0\n");
-		return -EINVAL;
+	if (priv->data->flags & FLAG_CFG0) {
+		regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!regs)
+			dev_err(dev, "missing mem resources for cfg0\n");
+		else {
+			priv->cfg0_base = devm_pci_remap_cfg_resource(dev, regs);
+			if (IS_ERR(priv->cfg0_base))
+				return PTR_ERR(priv->cfg0_base);
+		}
 	}
 
-	priv->cfg0_base = devm_pci_remap_cfg_resource(dev, regs);
-	if (IS_ERR(priv->cfg0_base))
-		return PTR_ERR(priv->cfg0_base);
-
-	/* CFG1 is optional */
-	if (priv->flags & FLAG_CFG1) {
+	if (priv->data->flags & FLAG_CFG1) {
 		regs = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 		if (!regs)
 			dev_info(dev, "missing mem resource for cfg1\n");
@@ -218,7 +245,7 @@ static int loongson_pci_probe(struct platform_device *pdev)
 	}
 
 	bridge->sysdata = priv;
-	bridge->ops = &loongson_pci_ops;
+	bridge->ops = priv->data->ops;
 	bridge->map_irq = loongson_map_irq;
 
 	return pci_host_probe(bridge);
-- 
2.27.0

[PATCH V14 3/7] PCI: loongson: Add ACPI init support

[Huacai Chen]

Loongson PCH (LS7A chipset) will be used by both MIPS-based and
LoongArch-based Loongson processors. MIPS-based Loongson uses FDT
while LoongArch-base Loongson uses ACPI, this patch add ACPI init
support for the driver in drivers/pci/controller/pci-loongson.c
because it is currently FDT-only.

LoongArch is a new RISC ISA, mainline support will come soon, and
documentations are here (in translation):

https://github.com/loongson/LoongArch-Documentation

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/acpi/pci_mcfg.c               | 10 +++++
 drivers/pci/controller/Kconfig        |  2 +-
 drivers/pci/controller/pci-loongson.c | 62 +++++++++++++++++++++++++--
 include/linux/pci-ecam.h              |  1 +
 4 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
index 63b98eae5e75..860014b89b8e 100644
--- a/drivers/acpi/pci_mcfg.c
+++ b/drivers/acpi/pci_mcfg.c
@@ -172,6 +172,16 @@ static struct mcfg_fixup mcfg_quirks[] = {
 	ALTRA_ECAM_QUIRK(1, 14),
 	ALTRA_ECAM_QUIRK(1, 15),
 #endif /* ARM64 */
+
+#ifdef CONFIG_LOONGARCH
+#define LOONGSON_ECAM_MCFG(table_id, seg) \
+	{ "LOONGS", table_id, 1, seg, MCFG_BUS_ANY, &loongson_pci_ecam_ops }
+
+	LOONGSON_ECAM_MCFG("\0", 0),
+	LOONGSON_ECAM_MCFG("LOONGSON", 0),
+	LOONGSON_ECAM_MCFG("\0", 1),
+	LOONGSON_ECAM_MCFG("LOONGSON", 1),
+#endif /* LOONGARCH */
 };
 
 static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
index b8d96d38064d..9dbd73898b47 100644
--- a/drivers/pci/controller/Kconfig
+++ b/drivers/pci/controller/Kconfig
@@ -293,7 +293,7 @@ config PCI_HYPERV_INTERFACE
 config PCI_LOONGSON
 	bool "LOONGSON PCI Controller"
 	depends on MACH_LOONGSON64 || COMPILE_TEST
-	depends on OF
+	depends on OF || ACPI
 	depends on PCI_QUIRKS
 	default MACH_LOONGSON64
 	help
diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 565453882ffe..a1222fc15454 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -9,6 +9,8 @@
 #include <linux/of_pci.h>
 #include <linux/pci.h>
 #include <linux/pci_ids.h>
+#include <linux/pci-acpi.h>
+#include <linux/pci-ecam.h>
 
 #include "../pci.h"
 
@@ -97,6 +99,18 @@ static void loongson_mrrs_quirk(struct pci_dev *dev)
 }
 DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk);
 
+static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
+{
+	struct pci_config_window *cfg;
+
+	if (acpi_disabled)
+		return (struct loongson_pci *)(bus->sysdata);
+	else {
+		cfg = bus->sysdata;
+		return (struct loongson_pci *)(cfg->priv);
+	}
+}
+
 static void __iomem *cfg1_map(struct loongson_pci *priv, int bus,
 				unsigned int devfn, int where)
 {
@@ -124,12 +138,14 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
 			       int where)
 {
 	unsigned char busnum = bus->number;
-	struct pci_host_bridge *bridge = pci_find_host_bridge(bus);
-	struct loongson_pci *priv =  pci_host_bridge_priv(bridge);
+	struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
+
+	if (pci_is_root_bus(bus))
+		busnum = 0;
 
 	/*
 	 * Do not read more than one device on the bus other than
-	 * the host bus. For our hardware the root bus is always bus 0.
+	 * the host bus.
 	 */
 	if (priv->data->flags & FLAG_DEV_FIX &&
 			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
@@ -146,6 +162,8 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
 	return NULL;
 }
 
+#ifdef CONFIG_OF
+
 static int loongson_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 {
 	int irq;
@@ -259,3 +277,41 @@ static struct platform_driver loongson_pci_driver = {
 	.probe = loongson_pci_probe,
 };
 builtin_platform_driver(loongson_pci_driver);
+
+#endif
+
+#ifdef CONFIG_ACPI
+
+static int loongson_pci_ecam_init(struct pci_config_window *cfg)
+{
+	struct device *dev = cfg->parent;
+	struct loongson_pci *priv;
+	struct loongson_pci_data *data;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	cfg->priv = priv;
+	data->flags = FLAG_CFG1;
+	priv->data = data;
+	priv->cfg1_base = cfg->win - (cfg->busr.start << 16);
+
+	return 0;
+}
+
+const struct pci_ecam_ops loongson_pci_ecam_ops = {
+	.bus_shift = 16,
+	.init	   = loongson_pci_ecam_init,
+	.pci_ops   = {
+		.map_bus = pci_loongson_map_bus,
+		.read	 = pci_generic_config_read,
+		.write	 = pci_generic_config_write,
+	}
+};
+
+#endif
diff --git a/include/linux/pci-ecam.h b/include/linux/pci-ecam.h
index adea5a4771cf..6b1301e2498e 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 loongson_pci_ecam_ops; /* Loongson PCIe */
 #endif
 
 #if IS_ENABLED(CONFIG_PCI_HOST_COMMON)
-- 
2.27.0

[PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Huacai Chen]

On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
scanning. This is a hardware flaw but we can only avoid it by software
now.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index a1222fc15454..e22142f75d97 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -134,10 +134,20 @@ static void __iomem *cfg0_map(struct loongson_pci *priv, int bus,
 	return priv->cfg0_base + addroff;
 }
 
+static bool pdev_is_existant(unsigned char bus, unsigned int device, unsigned int function)
+{
+	if ((bus == 0) && (device >= 9 && device <= 20) && (function > 0))
+		return false;
+
+	return true;
+}
+
 static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devfn,
 			       int where)
 {
 	unsigned char busnum = bus->number;
+	unsigned int device = PCI_SLOT(devfn);
+	unsigned int function = PCI_FUNC(devfn);
 	struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
 
 	if (pci_is_root_bus(bus))
@@ -147,8 +157,13 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
 	 * Do not read more than one device on the bus other than
 	 * the host bus.
 	 */
-	if (priv->data->flags & FLAG_DEV_FIX &&
-			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
+	if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
+		if (!pci_is_root_bus(bus) && (device > 0))
+			return NULL;
+	}
+
+	/* Don't access non-existant devices */
+	if (!pdev_is_existant(busnum, device, function))
 		return NULL;
 
 	/* CFG0 can only access standard space */
-- 
2.27.0

[PATCH V14 5/7] PCI: loongson: Improve the MRRS quirk for LS7A

[Huacai Chen]

In new revision of LS7A, some PCIe ports support larger value than 256,
but their maximum supported MRRS values are not detectable. Moreover,
the current loongson_mrrs_quirk() cannot avoid devices increasing its
MRRS after pci_enable_device(), and some devices (e.g. Realtek 8169)
will actually set a big value in its driver. So the only possible way
is configure MRRS of all devices in BIOS, and add a pci host bridge bit
flag (i.e., no_inc_mrrs) to stop the increasing MRRS operations.

However, according to PCIe Spec, it is legal for an OS to program any
value for MRRS, and it is also legal for an endpoint to generate a Read
Request with any size up to its MRRS. As the hardware engineers say, the
root cause here is LS7A doesn't break up large read requests. In detail,
LS7A PCIe port reports CA (Completer Abort) if it receives a Memory Read
request with a size that's "too big" ("too big" means larger than the
PCIe ports can handle, which means 256 for some ports and 4096 for the
others, and of course this is a problem in the LS7A's hardware design).

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 44 +++++++++------------------
 drivers/pci/pci.c                     |  6 ++++
 include/linux/pci.h                   |  1 +
 3 files changed, 22 insertions(+), 29 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index e22142f75d97..62ac91b2a5c5 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -67,37 +67,23 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_LS7A_LPC, system_bus_quirk);
 
-static void loongson_mrrs_quirk(struct pci_dev *dev)
+static void loongson_mrrs_quirk(struct pci_dev *pdev)
 {
-	struct pci_bus *bus = dev->bus;
-	struct pci_dev *bridge;
-	static const struct pci_device_id bridge_devids[] = {
-		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_0) },
-		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_1) },
-		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_2) },
-		{ 0, },
-	};
-
-	/* look for the matching bridge */
-	while (!pci_is_root_bus(bus)) {
-		bridge = bus->self;
-		bus = bus->parent;
-		/*
-		 * Some Loongson PCIe ports have a h/w limitation of
-		 * 256 bytes maximum read request size. They can't handle
-		 * anything larger than this. So force this limit on
-		 * any devices attached under these ports.
-		 */
-		if (pci_match_id(bridge_devids, bridge)) {
-			if (pcie_get_readrq(dev) > 256) {
-				pci_info(dev, "limiting MRRS to 256\n");
-				pcie_set_readrq(dev, 256);
-			}
-			break;
-		}
-	}
+	/*
+	 * Some Loongson PCIe ports have h/w limitations of maximum read
+	 * request size. They can't handle anything larger than this. So
+	 * force this limit on any devices attached under these ports.
+	 */
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	bridge->no_inc_mrrs = 1;
 }
-DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_0, loongson_mrrs_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_1, loongson_mrrs_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_2, loongson_mrrs_quirk);
 
 static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
 {
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index cfaf40a540a8..79157cbad835 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6052,6 +6052,7 @@ int pcie_set_readrq(struct pci_dev *dev, int rq)
 {
 	u16 v;
 	int ret;
+	struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
 
 	if (rq < 128 || rq > 4096 || !is_power_of_2(rq))
 		return -EINVAL;
@@ -6070,6 +6071,11 @@ int pcie_set_readrq(struct pci_dev *dev, int rq)
 
 	v = (ffs(rq) - 8) << 12;
 
+	if (bridge->no_inc_mrrs) {
+		if (rq > pcie_get_readrq(dev))
+			return -EINVAL;
+	}
+
 	ret = pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL,
 						  PCI_EXP_DEVCTL_READRQ, v);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 81a57b498f22..a9211074add6 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -569,6 +569,7 @@ struct pci_host_bridge {
 	void		*release_data;
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */
+	unsigned int	no_inc_mrrs:1;		/* No Increase MRRS */
 	unsigned int	native_aer:1;		/* OS may use PCIe AER */
 	unsigned int	native_pcie_hotplug:1;	/* OS may use PCIe hotplug */
 	unsigned int	native_shpc_hotplug:1;	/* OS may use SHPC hotplug */
-- 
2.27.0

[PATCH V14 6/7] PCI: Add quirk for LS7A to avoid reboot failure

[Huacai Chen]

cc27b735ad3a7557 ("PCI/portdrv: Turn off PCIe services during shutdown")
causes poweroff/reboot failure on systems with LS7A chipset. We found
that if we remove "pci_command &= ~PCI_COMMAND_MASTER" in do_pci_disable
_device(), it can work well. The hardware engineer says that the root
cause is that CPU is still accessing PCIe devices while poweroff/reboot,
and if we disable the Bus Master Bit at this time, the PCIe controller
doesn't forward requests to downstream devices, and also does not send
TIMEOUT to CPU, which causes CPU wait forever (hardware deadlock). This
behavior is a PCIe protocol violation (Bus Master should not be involved
in CPU MMIO transactions), and it will be fixed in new revisions of
hardware (add timeout mechanism for CPU read request, whether or not Bus
Master bit is cleared).

On some x86 platforms, radeon/amdgpu devices can cause similar problems
[1][2]. Once before I wanted to make a single patch to solve "all of
these problems" together, but it seems unreasonable because maybe they
are not exactly the same problem. So, this patch add a new function
pcie_portdrv_shutdown(), a slight modified copy of pcie_portdrv_remove()
dedicated for the shutdown path, and then add a quirk just for LS7A to
avoid clearing Bus Master bit in pcie_portdrv_shutdown(). Leave other
platforms behave as before.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=97980
[2] https://bugs.freedesktop.org/show_bug.cgi?id=98638

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 17 +++++++++++++++++
 drivers/pci/pcie/portdrv_core.c       |  1 -
 drivers/pci/pcie/portdrv_pci.c        | 20 +++++++++++++++++++-
 include/linux/pci.h                   |  1 +
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 62ac91b2a5c5..6d7276debcfd 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -85,6 +85,23 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_2, loongson_mrrs_quirk);
 
+static void loongson_bmaster_quirk(struct pci_dev *pdev)
+{
+	/*
+	 * Some Loongson PCIe ports will cause CPU deadlock if disable
+	 * the Bus Master bit during poweroff/reboot.
+	 */
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	bridge->no_dis_bmaster = 1;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_0, loongson_bmaster_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_1, loongson_bmaster_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_2, loongson_bmaster_quirk);
+
 static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
 {
 	struct pci_config_window *cfg;
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 604feeb84ee4..ee3d654dcbb4 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -493,7 +493,6 @@ void pcie_port_device_remove(struct pci_dev *dev)
 {
 	device_for_each_child(&dev->dev, NULL, remove_iter);
 	pci_free_irq_vectors(dev);
-	pci_disable_device(dev);
 }
 
 /**
diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 7f8788a970ae..f821f916d020 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -148,6 +148,24 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
 	}
 
 	pcie_port_device_remove(dev);
+
+	pci_disable_device(dev);
+}
+
+static void pcie_portdrv_shutdown(struct pci_dev *dev)
+{
+	struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
+
+	if (pci_bridge_d3_possible(dev)) {
+		pm_runtime_forbid(&dev->dev);
+		pm_runtime_get_noresume(&dev->dev);
+		pm_runtime_dont_use_autosuspend(&dev->dev);
+	}
+
+	pcie_port_device_remove(dev);
+
+	if (!bridge->no_dis_bmaster)
+		pci_disable_device(dev);
 }
 
 static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
@@ -198,7 +216,7 @@ static struct pci_driver pcie_portdriver = {
 
 	.probe		= pcie_portdrv_probe,
 	.remove		= pcie_portdrv_remove,
-	.shutdown	= pcie_portdrv_remove,
+	.shutdown	= pcie_portdrv_shutdown,
 
 	.err_handler	= &pcie_portdrv_err_handler,
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a9211074add6..0f0908679074 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -570,6 +570,7 @@ struct pci_host_bridge {
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */
 	unsigned int	no_inc_mrrs:1;		/* No Increase MRRS */
+	unsigned int	no_dis_bmaster:1;	/* No Disable Bus Master */
 	unsigned int	native_aer:1;		/* OS may use PCIe AER */
 	unsigned int	native_pcie_hotplug:1;	/* OS may use PCIe hotplug */
 	unsigned int	native_shpc_hotplug:1;	/* OS may use SHPC hotplug */
-- 
2.27.0

[PATCH V14 7/7] PCI: Add quirk for multifunction devices of LS7A

[Huacai Chen]

From: Jianmin Lv <lvjianmin@loongson.cn>

In LS7A, multifunction device use same PCI PIN (because the PIN register
report the same INTx value to each function) but we need different IRQ
for different functions, so add a quirk to fix it for standard PCI PIN
usage.

This patch only affect ACPI based systems (and only needed by ACPI based
systems, too). For DT based systems, the irq mappings is defined in .dts
files and be handled by of_irq_parse_pci().

Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 32 +++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 6d7276debcfd..e8ed3dfa188a 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -22,6 +22,13 @@
 #define DEV_LS2K_APB	0x7a02
 #define DEV_LS7A_CONF	0x7a10
 #define DEV_LS7A_LPC	0x7a0c
+#define DEV_LS7A_GMAC	0x7a03
+#define DEV_LS7A_DC1	0x7a06
+#define DEV_LS7A_DC2	0x7a36
+#define DEV_LS7A_GPU	0x7a15
+#define DEV_LS7A_AHCI	0x7a08
+#define DEV_LS7A_EHCI	0x7a14
+#define DEV_LS7A_OHCI	0x7a24
 
 #define FLAG_CFG0	BIT(0)
 #define FLAG_CFG1	BIT(1)
@@ -102,6 +109,31 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_2, loongson_bmaster_quirk);
 
+static void loongson_pci_pin_quirk(struct pci_dev *pdev)
+{
+	pdev->pin = 1 + (PCI_FUNC(pdev->devfn) & 3);
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_DC1, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_DC2, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_GPU, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_GMAC, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_AHCI, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_EHCI, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_OHCI, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_0, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_1, loongson_pci_pin_quirk);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_2, loongson_pci_pin_quirk);
+
 static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
 {
 	struct pci_config_window *cfg;
-- 
2.27.0

Re: [PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Bjorn Helgaas]

On Fri, Jun 17, 2022 at 03:43:27PM +0800, Huacai Chen wrote:
> On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
> scanning. This is a hardware flaw but we can only avoid it by software
> now.

We should say what *does* happen if we do a config read to a device
that doesn't exit.  Machine check, hang, etc?

> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
>  drivers/pci/controller/pci-loongson.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> index a1222fc15454..e22142f75d97 100644
> --- a/drivers/pci/controller/pci-loongson.c
> +++ b/drivers/pci/controller/pci-loongson.c
> @@ -134,10 +134,20 @@ static void __iomem *cfg0_map(struct loongson_pci *priv, int bus,
>  	return priv->cfg0_base + addroff;
>  }
>  
> +static bool pdev_is_existant(unsigned char bus, unsigned int device, unsigned int function)
> +{
> +	if ((bus == 0) && (device >= 9 && device <= 20) && (function > 0))
> +		return false;

Why do you test pci_is_root_bus() below and "bus == 0" here?  I think
you intend them both to test the same thing.  If so, I think you
should test for "if (pci_is_root_bus(bus) ..." here.

Generally speaking we only probe for functions > 0 if .0 is marked as
multi-function, so I guess this means 00:09.0 is marked as a
multi-function device, but config reads to 00:09.1 would fail?

> +	return true;

Returning "true" here means "the device *may* exist," not "this device
*does* exist," right?  If so, the function name probably should be
"pdev_may_exist()".

I guess that when we do a config read to a non-root bus device that
doesn't exist, e.g., "01:00.0", that read terminates with an
Unsupported Request error, the config read gets the ~0 data we expect?

> +}
> +
>  static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devfn,
>  			       int where)
>  {
>  	unsigned char busnum = bus->number;
> +	unsigned int device = PCI_SLOT(devfn);
> +	unsigned int function = PCI_FUNC(devfn);
>  	struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
>  
>  	if (pci_is_root_bus(bus))
> @@ -147,8 +157,13 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
>  	 * Do not read more than one device on the bus other than
>  	 * the host bus.
>  	 */
> -	if (priv->data->flags & FLAG_DEV_FIX &&
> -			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
> +	if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
> +		if (!pci_is_root_bus(bus) && (device > 0))
> +			return NULL;
> +	}
> +
> +	/* Don't access non-existant devices */
> +	if (!pdev_is_existant(busnum, device, function))
>  		return NULL;

Is this a "forever" hardware bug that will never be fixed, or should
there be a flag like FLAG_DEV_FIX so we only do this on the broken
devices?

>  	/* CFG0 can only access standard space */
> -- 
> 2.27.0
> 

Re: [PATCH V14 1/7] PCI/ACPI: Guard ARM64-specific mcfg_quirks

[Bjorn Helgaas]

On Fri, Jun 17, 2022 at 03:43:24PM +0800, Huacai Chen wrote:
> Guard ARM64-specific quirks with CONFIG_ARM64 to avoid build errors,
> since mcfg_quirks will be shared by more than one architectures.
> 
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

pci_mcfg.o is only built when CONFIG_ACPI_MCFG=y.  Where's the patch
that sets CONFIG_ACPI_MCFG=y for loongson?

I see that "PCI: loongson: Add ACPI init support" adds the #ifdef
CONFIG_LOONGARCH here, but AFAICS we still won't build it.

> ---
>  drivers/acpi/pci_mcfg.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> index 53cab975f612..63b98eae5e75 100644
> --- a/drivers/acpi/pci_mcfg.c
> +++ b/drivers/acpi/pci_mcfg.c
> @@ -41,6 +41,8 @@ struct mcfg_fixup {
>  static struct mcfg_fixup mcfg_quirks[] = {
>  /*	{ OEM_ID, OEM_TABLE_ID, REV, SEGMENT, BUS_RANGE, ops, cfgres }, */
>  
> +#ifdef CONFIG_ARM64
> +
>  #define AL_ECAM(table_id, rev, seg, ops) \
>  	{ "AMAZON", table_id, rev, seg, MCFG_BUS_ANY, ops }
>  
> @@ -169,6 +171,7 @@ static struct mcfg_fixup mcfg_quirks[] = {
>  	ALTRA_ECAM_QUIRK(1, 13),
>  	ALTRA_ECAM_QUIRK(1, 14),
>  	ALTRA_ECAM_QUIRK(1, 15),
> +#endif /* ARM64 */
>  };
>  
>  static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
> -- 
> 2.27.0
> 

Re: [PATCH V14 1/7] PCI/ACPI: Guard ARM64-specific mcfg_quirks

[Huacai Chen]

Hi, Bjorn,

On Tue, Jun 28, 2022 at 5:53 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Fri, Jun 17, 2022 at 03:43:24PM +0800, Huacai Chen wrote:
> > Guard ARM64-specific quirks with CONFIG_ARM64 to avoid build errors,
> > since mcfg_quirks will be shared by more than one architectures.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
>
> pci_mcfg.o is only built when CONFIG_ACPI_MCFG=y.  Where's the patch
> that sets CONFIG_ACPI_MCFG=y for loongson?
>
> I see that "PCI: loongson: Add ACPI init support" adds the #ifdef
> CONFIG_LOONGARCH here, but AFAICS we still won't build it.
MCFG is enabled by the arch-dependent patch "LoongArch: Add PCI
controller support". That one was in the arch series for 5.19, but in
the 5.19 merge window the PCI series was still under review so it was
dropped. When this PCI series is good enough, that one will be added
to 5.20 from the arch tree, I think.

Huacai
>
> > ---
> >  drivers/acpi/pci_mcfg.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> > index 53cab975f612..63b98eae5e75 100644
> > --- a/drivers/acpi/pci_mcfg.c
> > +++ b/drivers/acpi/pci_mcfg.c
> > @@ -41,6 +41,8 @@ struct mcfg_fixup {
> >  static struct mcfg_fixup mcfg_quirks[] = {
> >  /*   { OEM_ID, OEM_TABLE_ID, REV, SEGMENT, BUS_RANGE, ops, cfgres }, */
> >
> > +#ifdef CONFIG_ARM64
> > +
> >  #define AL_ECAM(table_id, rev, seg, ops) \
> >       { "AMAZON", table_id, rev, seg, MCFG_BUS_ANY, ops }
> >
> > @@ -169,6 +171,7 @@ static struct mcfg_fixup mcfg_quirks[] = {
> >       ALTRA_ECAM_QUIRK(1, 13),
> >       ALTRA_ECAM_QUIRK(1, 14),
> >       ALTRA_ECAM_QUIRK(1, 15),
> > +#endif /* ARM64 */
> >  };
> >
> >  static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
> > --
> > 2.27.0
> >

Re: [PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Jianmin Lv]

On 2022/6/28 上午5:38, Bjorn Helgaas wrote:
> On Fri, Jun 17, 2022 at 03:43:27PM +0800, Huacai Chen wrote:
>> On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
>> scanning. This is a hardware flaw but we can only avoid it by software
>> now.
> 
> We should say what *does* happen if we do a config read to a device
> that doesn't exit.  Machine check, hang, etc?
> 

The device is a hidden device(only for debug) that should not be 
scanned. If scanned in a non-normal way, the machine is hang(one case in 
ltp pci test can trigger the issue, which is explained blow).


>> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
>> ---
>>   drivers/pci/controller/pci-loongson.c | 19 +++++++++++++++++--
>>   1 file changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
>> index a1222fc15454..e22142f75d97 100644
>> --- a/drivers/pci/controller/pci-loongson.c
>> +++ b/drivers/pci/controller/pci-loongson.c
>> @@ -134,10 +134,20 @@ static void __iomem *cfg0_map(struct loongson_pci *priv, int bus,
>>   	return priv->cfg0_base + addroff;
>>   }
>>   
>> +static bool pdev_is_existant(unsigned char bus, unsigned int device, unsigned int function)
>> +{
>> +	if ((bus == 0) && (device >= 9 && device <= 20) && (function > 0))
>> +		return false;
> 
> Why do you test pci_is_root_bus() below and "bus == 0" here?  I think
> you intend them both to test the same thing.  If so, I think you
> should test for "if (pci_is_root_bus(bus) ..." here.
> 

I agree, I think we can only use pci_is_root_bus to do the work.


> Generally speaking we only probe for functions > 0 if .0 is marked as
> multi-function, so I guess this means 00:09.0 is marked as a
> multi-function device, but config reads to 00:09.1 would fail?
> 

Yes, definitely. Actually, the 00:09.0 is a single device, so fun1(09.1)
will not be scanned(e.g. the fun1 will be not scanned on pci enumeration
during kernel booting).

But, there is one situation: when running ltp pci test case on LS7A,
the 00:08.2 is a sata controller(a valid device), and the bus number(0)
and devfn(0x42) are inputted to kernel api pci_scan_slot(), which has
clear note: devfn must have zero function. So, apparently, the inputted
devfn's function is not zero, but 2, and then in the pci_scan_slot():


         for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, 
fn)) {
                 dev = pci_scan_single_device(bus, devfn + fn);
                 ...
         }


08.2,08.3...and 09.1 will be scanned one by one, so the 09.1(fun1) is
scanned.

>> +	return true;
> 
> Returning "true" here means "the device *may* exist," not "this device
> *does* exist," right?  If so, the function name probably should be
> "pdev_may_exist()".
> 

Yes, I think pdev_may_exist maybe better.

> I guess that when we do a config read to a non-root bus device that
> doesn't exist, e.g., "01:00.0", that read terminates with an
> Unsupported Request error, the config read gets the ~0 data we expect?
> 

Yes, I think so.

>> +}
>> +
>>   static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devfn,
>>   			       int where)
>>   {
>>   	unsigned char busnum = bus->number;
>> +	unsigned int device = PCI_SLOT(devfn);
>> +	unsigned int function = PCI_FUNC(devfn);
>>   	struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
>>   
>>   	if (pci_is_root_bus(bus))
>> @@ -147,8 +157,13 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
>>   	 * Do not read more than one device on the bus other than
>>   	 * the host bus.
>>   	 */
>> -	if (priv->data->flags & FLAG_DEV_FIX &&
>> -			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
>> +	if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
>> +		if (!pci_is_root_bus(bus) && (device > 0))
>> +			return NULL;
>> +	}
>> +
>> +	/* Don't access non-existant devices */
>> +	if (!pdev_is_existant(busnum, device, function))
>>   		return NULL;
> 
> Is this a "forever" hardware bug that will never be fixed, or should
> there be a flag like FLAG_DEV_FIX so we only do this on the broken
> devices?
> 

No, the next new version LS7A will correct it, so maybe we can use 
FLAG_DEV_FIX-like to address it.

>>   	/* CFG0 can only access standard space */
>> -- 
>> 2.27.0
>>

Re: [PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Bjorn Helgaas]

On Tue, Jun 28, 2022 at 09:03:02PM +0800, Jianmin Lv wrote:
> On 2022/6/28 上午5:38, Bjorn Helgaas wrote:
> > On Fri, Jun 17, 2022 at 03:43:27PM +0800, Huacai Chen wrote:
> > > On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
> > > scanning. This is a hardware flaw but we can only avoid it by software
> > > now.
> > 
> > We should say what *does* happen if we do a config read to a device
> > that doesn't exit.  Machine check, hang, etc?
> 
> The device is a hidden device(only for debug) that should not be
> scanned. If scanned in a non-normal way, the machine is hang(one
> case in ltp pci test can trigger the issue, which is explained
> below).

Reading the Vendor ID is the *normal* way to scan for a device.  It
seems that this hardware just hangs in some cases when the device
doesn't exist.

> > Generally speaking we only probe for functions > 0 if .0 is marked as
> > multi-function, so I guess this means 00:09.0 is marked as a
> > multi-function device, but config reads to 00:09.1 would fail?
> 
> Yes, definitely. Actually, the 00:09.0 is a single device, so fun1(09.1)
> will not be scanned(e.g. the fun1 will be not scanned on pci enumeration
> during kernel booting).
> 
> But, there is one situation: when running ltp pci test case on LS7A,
> the 00:08.2 is a sata controller(a valid device), and the bus number(0)
> and devfn(0x42) are inputted to kernel api pci_scan_slot(), which has
> clear note: devfn must have zero function. So, apparently, the inputted
> devfn's function is not zero, but 2, and then in the pci_scan_slot():
> 
>         for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn))
> {
>                 dev = pci_scan_single_device(bus, devfn + fn);
>                 ...
>         }
> 
> 08.2,08.3...and 09.1 will be scanned one by one, so the 09.1(fun1) is
> scanned.

Does the "((bus == 0) && (device >= 9 && device <= 20) && (function > 0))"
test catch *all* devfns where the hang occurs?  I wouldn't want to
only avoid the ones that LTP happens to use.  If we did that, a future
LTP change could easily break things again.  But I assume you know
exactly what devices are present on the root bus.

> > > -	if (priv->data->flags & FLAG_DEV_FIX &&
> > > -			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
> > > +	if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
> > > +		if (!pci_is_root_bus(bus) && (device > 0))
> > > +			return NULL;
> > > +	}
> > > +
> > > +	/* Don't access non-existant devices */
> > > +	if (!pdev_is_existant(busnum, device, function))
> > >   		return NULL;
> > 
> > Is this a "forever" hardware bug that will never be fixed, or should
> > there be a flag like FLAG_DEV_FIX so we only do this on the broken
> > devices?
> 
> No, the next new version LS7A will correct it, so maybe we can use
> FLAG_DEV_FIX-like to address it.

You should add the flag now instead of waiting for the new hardware.
Otherwise you may not remember or notice the need to make this
conditional on the hardware version, you'll wonder why the fixed
hardware doesn't enumerate devices correctly.

Bjorn

Re: [PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Jianmin Lv]

On 2022/6/29 上午12:04, Bjorn Helgaas wrote:
> On Tue, Jun 28, 2022 at 09:03:02PM +0800, Jianmin Lv wrote:
>> On 2022/6/28 上午5:38, Bjorn Helgaas wrote:
>>> On Fri, Jun 17, 2022 at 03:43:27PM +0800, Huacai Chen wrote:
>>>> On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
>>>> scanning. This is a hardware flaw but we can only avoid it by software
>>>> now.
>>>
>>> We should say what *does* happen if we do a config read to a device
>>> that doesn't exit.  Machine check, hang, etc?
>>
>> The device is a hidden device(only for debug) that should not be
>> scanned. If scanned in a non-normal way, the machine is hang(one
>> case in ltp pci test can trigger the issue, which is explained
>> below).
> 
> Reading the Vendor ID is the *normal* way to scan for a device.  It
> seems that this hardware just hangs in some cases when the device
> doesn't exist.
> 
>>> Generally speaking we only probe for functions > 0 if .0 is marked as
>>> multi-function, so I guess this means 00:09.0 is marked as a
>>> multi-function device, but config reads to 00:09.1 would fail?
>>
>> Yes, definitely. Actually, the 00:09.0 is a single device, so fun1(09.1)
>> will not be scanned(e.g. the fun1 will be not scanned on pci enumeration
>> during kernel booting).
>>
>> But, there is one situation: when running ltp pci test case on LS7A,
>> the 00:08.2 is a sata controller(a valid device), and the bus number(0)
>> and devfn(0x42) are inputted to kernel api pci_scan_slot(), which has
>> clear note: devfn must have zero function. So, apparently, the inputted
>> devfn's function is not zero, but 2, and then in the pci_scan_slot():
>>
>>          for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn))
>> {
>>                  dev = pci_scan_single_device(bus, devfn + fn);
>>                  ...
>>          }
>>
>> 08.2,08.3...and 09.1 will be scanned one by one, so the 09.1(fun1) is
>> scanned.
> 
> Does the "((bus == 0) && (device >= 9 && device <= 20) && (function > 0))"
> test catch *all* devfns where the hang occurs?  I wouldn't want to
> only avoid the ones that LTP happens to use.  If we did that, a future
> LTP change could easily break things again.  But I assume you know
> exactly what devices are present on the root bus.
> 

Yes, as you said, I'm sure that only these hidden functions(fun1 of dev 
9 to 20) on root bus can cause issue, so this fix is enough to address it.

>>>> -	if (priv->data->flags & FLAG_DEV_FIX &&
>>>> -			!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
>>>> +	if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
>>>> +		if (!pci_is_root_bus(bus) && (device > 0))
>>>> +			return NULL;
>>>> +	}
>>>> +
>>>> +	/* Don't access non-existant devices */
>>>> +	if (!pdev_is_existant(busnum, device, function))
>>>>    		return NULL;
>>>
>>> Is this a "forever" hardware bug that will never be fixed, or should
>>> there be a flag like FLAG_DEV_FIX so we only do this on the broken
>>> devices?
>>
>> No, the next new version LS7A will correct it, so maybe we can use
>> FLAG_DEV_FIX-like to address it.
> 
> You should add the flag now instead of waiting for the new hardware.
> Otherwise you may not remember or notice the need to make this
> conditional on the hardware version, you'll wonder why the fixed
> hardware doesn't enumerate devices correctly.
> 

Thanks for your suggestion, I agree that, Huacai, WDYT?


> Bjorn
> 

Re: [PATCH V14 4/7] PCI: loongson: Don't access non-existant devices

[Huacai Chen]

Hi, Jianmin and Bjorn,

On Wed, Jun 29, 2022 at 8:33 AM Jianmin Lv <lvjianmin@loongson.cn> wrote:
>
>
>
> On 2022/6/29 上午12:04, Bjorn Helgaas wrote:
> > On Tue, Jun 28, 2022 at 09:03:02PM +0800, Jianmin Lv wrote:
> >> On 2022/6/28 上午5:38, Bjorn Helgaas wrote:
> >>> On Fri, Jun 17, 2022 at 03:43:27PM +0800, Huacai Chen wrote:
> >>>> On LS2K/LS7A, some non-existant devices don't return 0xffffffff when
> >>>> scanning. This is a hardware flaw but we can only avoid it by software
> >>>> now.
> >>>
> >>> We should say what *does* happen if we do a config read to a device
> >>> that doesn't exit.  Machine check, hang, etc?
> >>
> >> The device is a hidden device(only for debug) that should not be
> >> scanned. If scanned in a non-normal way, the machine is hang(one
> >> case in ltp pci test can trigger the issue, which is explained
> >> below).
> >
> > Reading the Vendor ID is the *normal* way to scan for a device.  It
> > seems that this hardware just hangs in some cases when the device
> > doesn't exist.
> >
> >>> Generally speaking we only probe for functions > 0 if .0 is marked as
> >>> multi-function, so I guess this means 00:09.0 is marked as a
> >>> multi-function device, but config reads to 00:09.1 would fail?
> >>
> >> Yes, definitely. Actually, the 00:09.0 is a single device, so fun1(09.1)
> >> will not be scanned(e.g. the fun1 will be not scanned on pci enumeration
> >> during kernel booting).
> >>
> >> But, there is one situation: when running ltp pci test case on LS7A,
> >> the 00:08.2 is a sata controller(a valid device), and the bus number(0)
> >> and devfn(0x42) are inputted to kernel api pci_scan_slot(), which has
> >> clear note: devfn must have zero function. So, apparently, the inputted
> >> devfn's function is not zero, but 2, and then in the pci_scan_slot():
> >>
> >>          for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn))
> >> {
> >>                  dev = pci_scan_single_device(bus, devfn + fn);
> >>                  ...
> >>          }
> >>
> >> 08.2,08.3...and 09.1 will be scanned one by one, so the 09.1(fun1) is
> >> scanned.
> >
> > Does the "((bus == 0) && (device >= 9 && device <= 20) && (function > 0))"
> > test catch *all* devfns where the hang occurs?  I wouldn't want to
> > only avoid the ones that LTP happens to use.  If we did that, a future
> > LTP change could easily break things again.  But I assume you know
> > exactly what devices are present on the root bus.
> >
>
> Yes, as you said, I'm sure that only these hidden functions(fun1 of dev
> 9 to 20) on root bus can cause issue, so this fix is enough to address it.
>
> >>>> -  if (priv->data->flags & FLAG_DEV_FIX &&
> >>>> -                  !pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
> >>>> +  if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
> >>>> +          if (!pci_is_root_bus(bus) && (device > 0))
> >>>> +                  return NULL;
> >>>> +  }
> >>>> +
> >>>> +  /* Don't access non-existant devices */
> >>>> +  if (!pdev_is_existant(busnum, device, function))
> >>>>                    return NULL;
> >>>
> >>> Is this a "forever" hardware bug that will never be fixed, or should
> >>> there be a flag like FLAG_DEV_FIX so we only do this on the broken
> >>> devices?
> >>
> >> No, the next new version LS7A will correct it, so maybe we can use
> >> FLAG_DEV_FIX-like to address it.
> >
> > You should add the flag now instead of waiting for the new hardware.
> > Otherwise you may not remember or notice the need to make this
> > conditional on the hardware version, you'll wonder why the fixed
> > hardware doesn't enumerate devices correctly.
> >
>
> Thanks for your suggestion, I agree that, Huacai, WDYT?
Agree, I think we can use a FLAG_DEV_HIDDEN flag.

Huacai
>
>
> > Bjorn
> >
>