PCI: only save/restore existent registers in the PCIe capability

PCIe 1.1 base neither requires the endpoint to implement the entire
PCIe capability structure nor specifies default values of registers
that are not implemented by the device. So we only save and restore
registers that must be implemented by different device types if the
device PCIe capability version is 1.

PCIe 1.1 Capability Structure Expansion ECN and PCIe 2.0 requires
all registers in the PCIe capability to be either implemented or
hardwired to 0. Their PCIe capability version is 2.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.c

@@ -681,11 +681,34 @@ EXPORT_SYMBOL(pci_choose_state);
 
 #define PCI_EXP_SAVE_REGS	7
 
+#define pcie_cap_has_devctl(type, flags)	1
+#define pcie_cap_has_lnkctl(type, flags)		\
+		((flags & PCI_EXP_FLAGS_VERS) > 1 ||	\
+		 (type == PCI_EXP_TYPE_ROOT_PORT ||	\
+		  type == PCI_EXP_TYPE_ENDPOINT ||	\
+		  type == PCI_EXP_TYPE_LEG_END))
+#define pcie_cap_has_sltctl(type, flags)		\
+		((flags & PCI_EXP_FLAGS_VERS) > 1 ||	\
+		 ((type == PCI_EXP_TYPE_ROOT_PORT) ||	\
+		  (type == PCI_EXP_TYPE_DOWNSTREAM &&	\
+		   (flags & PCI_EXP_FLAGS_SLOT))))
+#define pcie_cap_has_rtctl(type, flags)			\
+		((flags & PCI_EXP_FLAGS_VERS) > 1 ||	\
+		 (type == PCI_EXP_TYPE_ROOT_PORT ||	\
+		  type == PCI_EXP_TYPE_RC_EC))
+#define pcie_cap_has_devctl2(type, flags)		\
+		((flags & PCI_EXP_FLAGS_VERS) > 1)
+#define pcie_cap_has_lnkctl2(type, flags)		\
+		((flags & PCI_EXP_FLAGS_VERS) > 1)
+#define pcie_cap_has_sltctl2(type, flags)		\
+		((flags & PCI_EXP_FLAGS_VERS) > 1)
+
 static int pci_save_pcie_state(struct pci_dev *dev)
 {
 	int pos, i = 0;
 	struct pci_cap_saved_state *save_state;
 	u16 *cap;
+	u16 flags;
 
 	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
 	if (pos <= 0)
@@ -698,12 +721,21 @@ static int pci_save_pcie_state(struct pci_dev *dev)
 	}
 	cap = (u16 *)&save_state->data[0];
 
+	pci_read_config_word(dev, pos + PCI_EXP_FLAGS, &flags);
+
+	if (pcie_cap_has_devctl(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_DEVCTL, &cap[i++]);
+	if (pcie_cap_has_lnkctl(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_LNKCTL, &cap[i++]);
+	if (pcie_cap_has_sltctl(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_SLTCTL, &cap[i++]);
+	if (pcie_cap_has_rtctl(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_RTCTL, &cap[i++]);
+	if (pcie_cap_has_devctl2(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &cap[i++]);
+	if (pcie_cap_has_lnkctl2(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_LNKCTL2, &cap[i++]);
+	if (pcie_cap_has_sltctl2(dev->pcie_type, flags))
 		pci_read_config_word(dev, pos + PCI_EXP_SLTCTL2, &cap[i++]);
 
 	return 0;
@@ -714,6 +746,7 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
 	int i = 0, pos;
 	struct pci_cap_saved_state *save_state;
 	u16 *cap;
+	u16 flags;
 
 	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
 	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
@@ -721,12 +754,21 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
 		return;
 	cap = (u16 *)&save_state->data[0];
 
+	pci_read_config_word(dev, pos + PCI_EXP_FLAGS, &flags);
+
+	if (pcie_cap_has_devctl(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_DEVCTL, cap[i++]);
+	if (pcie_cap_has_lnkctl(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_LNKCTL, cap[i++]);
+	if (pcie_cap_has_sltctl(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_SLTCTL, cap[i++]);
+	if (pcie_cap_has_rtctl(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_RTCTL, cap[i++]);
+	if (pcie_cap_has_devctl2(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, cap[i++]);
+	if (pcie_cap_has_lnkctl2(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_LNKCTL2, cap[i++]);
+	if (pcie_cap_has_sltctl2(dev->pcie_type, flags))
 		pci_write_config_word(dev, pos + PCI_EXP_SLTCTL2, cap[i++]);
 }
 

include/linux/pci_regs.h

@@ -376,6 +376,7 @@
 #define  PCI_EXP_TYPE_DOWNSTREAM 0x6	/* Downstream Port */
 #define  PCI_EXP_TYPE_PCI_BRIDGE 0x7	/* PCI/PCI-X Bridge */
 #define  PCI_EXP_TYPE_RC_END	0x9	/* Root Complex Integrated Endpoint */
+#define  PCI_EXP_TYPE_RC_EC	0x10	/* Root Complex Event Collector */
 #define PCI_EXP_FLAGS_SLOT	0x0100	/* Slot implemented */
 #define PCI_EXP_FLAGS_IRQ	0x3e00	/* Interrupt message number */
 #define PCI_EXP_DEVCAP		4	/* Device capabilities */