linux-kernel - [PATCH 02/22] PCI: Unify PCI error response checking

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Message-Id: <c632b07eb1b08cc7d4346455a55641436a379abd.1633972263.git.naveennaidu479@gmail.com>
Date:   Mon, 11 Oct 2021 23:08:32 +0530
From:   Naveen Naidu <naveennaidu479@...il.com>
To:     bhelgaas@...gle.com
Cc:     Naveen Naidu <naveennaidu479@...il.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 02/22] PCI: Unify PCI error response checking

An MMIO read from a PCI device that doesn't exist or doesn't respond
causes a PCI error.  There's no real data to return to satisfy the
CPU read, so most hardware fabricates ~0 data.

Use SET_PCI_ERROR_RESPONSE() to set the error response and
RESPONSE_IS_PCI_ERROR() to check the error response during hardware
read.

These definitions make error checks consistent and easier to find.

Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
---
 drivers/pci/access.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 46935695cfb9..e1954bbbd137 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -81,7 +81,7 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
 
 	addr = bus->ops->map_bus(bus, devfn, where);
 	if (!addr) {
-		*val = ~0;
+		SET_PCI_ERROR_RESPONSE(val);
 		return PCIBIOS_DEVICE_NOT_FOUND;
 	}
 
@@ -123,7 +123,7 @@ int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn,
 
 	addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
 	if (!addr) {
-		*val = ~0;
+		SET_PCI_ERROR_RESPONSE(val);
 		return PCIBIOS_DEVICE_NOT_FOUND;
 	}
 
@@ -411,10 +411,10 @@ int pcie_capability_read_word(struct pci_dev *dev, int pos, u16 *val)
 		ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
 		/*
 		 * Reset *val to 0 if pci_read_config_word() fails, it may
-		 * have been written as 0xFFFF if hardware error happens
-		 * during pci_read_config_word().
+		 * have been written as 0xFFFF (PCI_ERROR_RESPONSE) if hardware error
+		 * happens during pci_read_config_word().
 		 */
-		if (ret)
+		if (RESPONSE_IS_PCI_ERROR(val))
 			*val = 0;
 		return ret;
 	}
@@ -446,10 +446,10 @@ int pcie_capability_read_dword(struct pci_dev *dev, int pos, u32 *val)
 		ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
 		/*
 		 * Reset *val to 0 if pci_read_config_dword() fails, it may
-		 * have been written as 0xFFFFFFFF if hardware error happens
-		 * during pci_read_config_dword().
+		 * have been written as 0xFFFFFFFF (PCI_ERROR_RESPONSE) if hardware
+		 * error happens during pci_read_config_dword().
 		 */
-		if (ret)
+		if (RESPONSE_IS_PCI_ERROR(val))
 			*val = 0;
 		return ret;
 	}
@@ -523,7 +523,7 @@ EXPORT_SYMBOL(pcie_capability_clear_and_set_dword);
 int pci_read_config_byte(const struct pci_dev *dev, int where, u8 *val)
 {
 	if (pci_dev_is_disconnected(dev)) {
-		*val = ~0;
+		SET_PCI_ERROR_RESPONSE(val);
 		return PCIBIOS_DEVICE_NOT_FOUND;
 	}
 	return pci_bus_read_config_byte(dev->bus, dev->devfn, where, val);
@@ -533,7 +533,7 @@ EXPORT_SYMBOL(pci_read_config_byte);
 int pci_read_config_word(const struct pci_dev *dev, int where, u16 *val)
 {
 	if (pci_dev_is_disconnected(dev)) {
-		*val = ~0;
+		SET_PCI_ERROR_RESPONSE(val);
 		return PCIBIOS_DEVICE_NOT_FOUND;
 	}
 	return pci_bus_read_config_word(dev->bus, dev->devfn, where, val);
@@ -544,7 +544,7 @@ int pci_read_config_dword(const struct pci_dev *dev, int where,
 					u32 *val)
 {
 	if (pci_dev_is_disconnected(dev)) {
-		*val = ~0;
+		SET_PCI_ERROR_RESPONSE(val);
 		return PCIBIOS_DEVICE_NOT_FOUND;
 	}
 	return pci_bus_read_config_dword(dev->bus, dev->devfn, where, val);
-- 
2.25.1