PCI: pci-bridge-emul: Add support for PCIe extended capabilities

Add support for PCIe extended capabilities, which we just redirect to the
emulating driver.

[pali: Fix writing new value with W1C bits]
Link: https://lore.kernel.org/r/20220222155030.988-3-pali@kernel.org
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: Russell King

drivers/pci/pci-bridge-emul.c

@@ -437,26 +437,37 @@ int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
 		read_op = bridge->ops->read_pcie;
 		cfgspace = (__le32 *) &bridge->pcie_conf;
 		behavior = bridge->pcie_cap_regs_behavior;
-	} else {
-		/* Beyond our PCIe space */
+	} else if (reg < PCI_CFG_SPACE_SIZE) {
+		/* Rest of PCI space not implemented */
 		*value = 0;
 		return PCIBIOS_SUCCESSFUL;
+	} else {
+		/* PCIe extended capability space */
+		reg -= PCI_CFG_SPACE_SIZE;
+		read_op = bridge->ops->read_ext;
+		cfgspace = NULL;
+		behavior = NULL;
 	}
 
 	if (read_op)
 		ret = read_op(bridge, reg, value);
 	else
 		ret = PCI_BRIDGE_EMUL_NOT_HANDLED;
 
-	if (ret == PCI_BRIDGE_EMUL_NOT_HANDLED)
-		*value = le32_to_cpu(cfgspace[reg / 4]);
+	if (ret == PCI_BRIDGE_EMUL_NOT_HANDLED) {
+		if (cfgspace)
+			*value = le32_to_cpu(cfgspace[reg / 4]);
+		else
+			*value = 0;
+	}
 
 	/*
 	 * Make sure we never return any reserved bit with a value
 	 * different from 0.
 	 */
-	*value &= behavior[reg / 4].ro | behavior[reg / 4].rw |
-		  behavior[reg / 4].w1c;
+	if (behavior)
+		*value &= behavior[reg / 4].ro | behavior[reg / 4].rw |
+			  behavior[reg / 4].w1c;
 
 	if (size == 1)
 		*value = (*value >> (8 * (where & 3))) & 0xff;
@@ -502,8 +513,15 @@ int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
 		write_op = bridge->ops->write_pcie;
 		cfgspace = (__le32 *) &bridge->pcie_conf;
 		behavior = bridge->pcie_cap_regs_behavior;
-	} else {
+	} else if (reg < PCI_CFG_SPACE_SIZE) {
+		/* Rest of PCI space not implemented */
 		return PCIBIOS_SUCCESSFUL;
+	} else {
+		/* PCIe extended capability space */
+		reg -= PCI_CFG_SPACE_SIZE;
+		write_op = bridge->ops->write_ext;
+		cfgspace = NULL;
+		behavior = NULL;
 	}
 
 	shift = (where & 0x3) * 8;
@@ -517,29 +535,38 @@ int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
 	else
 		return PCIBIOS_BAD_REGISTER_NUMBER;
 
-	/* Keep all bits, except the RW bits */
-	new = old & (~mask | ~behavior[reg / 4].rw);
+	if (behavior) {
+		/* Keep all bits, except the RW bits */
+		new = old & (~mask | ~behavior[reg / 4].rw);
 
-	/* Update the value of the RW bits */
-	new |= (value << shift) & (behavior[reg / 4].rw & mask);
+		/* Update the value of the RW bits */
+		new |= (value << shift) & (behavior[reg / 4].rw & mask);
 
-	/* Clear the W1C bits */
-	new &= ~((value << shift) & (behavior[reg / 4].w1c & mask));
+		/* Clear the W1C bits */
+		new &= ~((value << shift) & (behavior[reg / 4].w1c & mask));
+	} else {
+		new = old & ~mask;
+		new |= (value << shift) & mask;
+	}
 
-	/* Save the new value with the cleared W1C bits into the cfgspace */
-	cfgspace[reg / 4] = cpu_to_le32(new);
+	if (cfgspace) {
+		/* Save the new value with the cleared W1C bits into the cfgspace */
+		cfgspace[reg / 4] = cpu_to_le32(new);
+	}
 
-	/*
-	 * Clear the W1C bits not specified by the write mask, so that the
-	 * write_op() does not clear them.
-	 */
-	new &= ~(behavior[reg / 4].w1c & ~mask);
+	if (behavior) {
+		/*
+		 * Clear the W1C bits not specified by the write mask, so that the
+		 * write_op() does not clear them.
+		 */
+		new &= ~(behavior[reg / 4].w1c & ~mask);
 
-	/*
-	 * Set the W1C bits specified by the write mask, so that write_op()
-	 * knows about that they are to be cleared.
-	 */
-	new |= (value << shift) & (behavior[reg / 4].w1c & mask);
+		/*
+		 * Set the W1C bits specified by the write mask, so that write_op()
+		 * knows about that they are to be cleared.
+		 */
+		new |= (value << shift) & (behavior[reg / 4].w1c & mask);
+	}
 
 	if (write_op)
 		write_op(bridge, reg, old, new, mask);

drivers/pci/pci-bridge-emul.h

@@ -90,6 +90,14 @@ struct pci_bridge_emul_ops {
 	 */
 	pci_bridge_emul_read_status_t (*read_pcie)(struct pci_bridge_emul *bridge,
 						   int reg, u32 *value);
+
+	/*
+	 * Same as ->read_base(), except it is for reading from the
+	 * PCIe extended capability configuration space.
+	 */
+	pci_bridge_emul_read_status_t (*read_ext)(struct pci_bridge_emul *bridge,
+						  int reg, u32 *value);
+
 	/*
 	 * Called when writing to the regular PCI bridge configuration
 	 * space. old is the current value, new is the new value being
@@ -105,6 +113,13 @@ struct pci_bridge_emul_ops {
 	 */
 	void (*write_pcie)(struct pci_bridge_emul *bridge, int reg,
 			   u32 old, u32 new, u32 mask);
+
+	/*
+	 * Same as ->write_base(), except it is for writing from the
+	 * PCIe extended capability configuration space.
+	 */
+	void (*write_ext)(struct pci_bridge_emul *bridge, int reg,
+			  u32 old, u32 new, u32 mask);
 };
 
 struct pci_bridge_reg_behavior;