diff mbox series

[v6,2/4] PCI/portdrv: Consolidate comments

Message ID 20171020162211.6391.34085.stgit@bhelgaas-glaptop.roam.corp.google.com
State Accepted
Headers show
Series PCI/portdrv: Fix MSI/MSI-X bug for PCIe port service drivers | expand

Commit Message

Bjorn Helgaas Oct. 20, 2017, 4:22 p.m. UTC 
From: Bjorn Helgaas <bhelgaas@google.com>

Consolidate some repetitive comments so we can see the code better.  No
functional change.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/pci/pcie/portdrv_core.c |   63 ++++++---------------------------------
 1 file changed, 9 insertions(+), 54 deletions(-)
diff mbox series

Patch

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 72fcbe5567dd..accd16082348 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -56,40 +56,27 @@  static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 {
 	int nr_entries, entry, nvec = 0;
 
-	/*
-	 * Allocate as many entries as the port wants, so that we can check
-	 * which of them will be useful.  Moreover, if nr_entries is correctly
-	 * equal to the number of entries this port actually uses, we'll happily
-	 * go through without any tricks.
-	 */
+	/* Allocate the maximum possible number of MSI/MSI-X vectors */
 	nr_entries = pci_alloc_irq_vectors(dev, 1, PCIE_PORT_MAX_MSI_ENTRIES,
 			PCI_IRQ_MSIX | PCI_IRQ_MSI);
 	if (nr_entries < 0)
 		return nr_entries;
 
+	/*
+	 * The Interrupt Message Number indicates which vector is used, i.e.,
+	 * the MSI-X table entry or the MSI offset between the base Message
+	 * Data and the generated interrupt message.  See PCIe r3.1, sec
+	 * 7.8.2, 7.10.10, 7.31.2.
+	 */
 	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP)) {
 		u16 reg16;
 
-		/*
-		 * Per PCIe r3.1, sec 6.1.6, "PME and Hot-Plug Event
-		 * interrupts (when both are implemented) always share the
-		 * same MSI or MSI-X vector, as indicated by the Interrupt
-		 * Message Number field in the PCI Express Capabilities
-		 * register".
-		 *
-		 * Per sec 7.8.2, "For MSI, the [Interrupt Message Number]
-		 * indicates the offset between the base Message Data and
-		 * the interrupt message that is generated."
-		 *
-		 * "For MSI-X, the [Interrupt Message Number] indicates
-		 * which MSI-X Table entry is used to generate the
-		 * interrupt message."
-		 */
 		pcie_capability_read_word(dev, PCI_EXP_FLAGS, &reg16);
 		entry = (reg16 & PCI_EXP_FLAGS_IRQ) >> 9;
 		if (entry >= nr_entries)
 			goto out_free_irqs;
 
+		/* PME and hotplug share an MSI/MSI-X vector */
 		irqs[PCIE_PORT_SERVICE_PME_SHIFT] = pci_irq_vector(dev, entry);
 		irqs[PCIE_PORT_SERVICE_HP_SHIFT] = pci_irq_vector(dev, entry);
 
@@ -99,19 +86,6 @@  static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 	if (mask & PCIE_PORT_SERVICE_AER) {
 		u32 reg32, pos;
 
-		/*
-		 * Per PCIe r3.1, sec 7.10.10, the Advanced Error Interrupt
-		 * Message Number in the Root Error Status register
-		 * indicates which MSI/MSI-X vector is used for AER.
-		 *
-		 * "For MSI, the [Advanced Error Interrupt Message Number]
-		 * indicates the offset between the base Message Data and
-		 * the interrupt message that is generated."
-		 *
-		 * "For MSI-X, the [Advanced Error Interrupt Message
-		 * Number] indicates which MSI-X Table entry is used to
-		 * generate the interrupt message."
-		 */
 		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
 		pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &reg32);
 		entry = (reg32 & PCI_ERR_ROOT_AER_IRQ) >> 27;
@@ -126,19 +100,6 @@  static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 	if (mask & PCIE_PORT_SERVICE_DPC) {
 		u16 reg16, pos;
 
-		/*
-		 * Per PCIe r4.0 (v0.9), sec 7.9.15.2, the DPC Interrupt
-		 * Message Number in the DPC Capability register indicates
-		 * which MSI/MSI-X vector is used for DPC.
-		 *
-		 * "For MSI, the [DPC Interrupt Message Number] indicates
-		 * the offset between the base Message Data and the
-		 * interrupt message that is generated."
-		 *
-		 * "For MSI-X, the [DPC Interrupt Message Number] indicates
-		 * which MSI-X Table entry is used to generate the
-		 * interrupt message."
-		 */
 		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC);
 		pci_read_config_word(dev, pos + PCI_EXP_DPC_CAP, &reg16);
 		entry = reg16 & PCI_EXP_DPC_IRQ;
@@ -150,16 +111,10 @@  static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 		nvec = max(nvec, entry + 1);
 	}
 
-	/*
-	 * If nvec is equal to the allocated number of entries, we can just use
-	 * what we have.  Otherwise, the port has some extra entries not for the
-	 * services we know and we need to work around that.
-	 */
+	/* If we allocated more than we need, free them and allocate fewer */
 	if (nvec != nr_entries) {
-		/* Drop the temporary MSI-X setup */
 		pci_free_irq_vectors(dev);
 
-		/* Now allocate the MSI-X vectors for real */
 		nr_entries = pci_alloc_irq_vectors(dev, nvec, nvec,
 				PCI_IRQ_MSIX | PCI_IRQ_MSI);
 		if (nr_entries < 0)