[PATCH 5/6] AHCI: Request multiple MSIs

[Matthew Wilcox]

AHCI controllers can support up to 16 interrupts, one per port.  This
saves us a readl() in the interrupt path to determine which port has
generated the interrupt.

Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
---
 drivers/ata/ahci.c |  104 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 99 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 5e6468a..a3f6331 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -102,6 +102,7 @@ enum {
 	/* HOST_CTL bits */
 	HOST_RESET		= (1 << 0),  /* reset controller; self-clear */
 	HOST_IRQ_EN		= (1 << 1),  /* global IRQ enable */
+	HOST_MSI_RSM		= (1 << 2),  /* Revert to Single Message */
 	HOST_AHCI_EN		= (1 << 31), /* AHCI enabled */
 
 	/* HOST_CAP bits */
@@ -1771,6 +1772,19 @@ static void ahci_port_intr(struct ata_port *ap)
 	}
 }
 
+static irqreturn_t ahci_msi_interrupt(int irq, void *dev_instance)
+{
+	struct ata_host *host = dev_instance;
+	int port = get_irq_subchannel(irq);
+	struct ata_port *ap = host->ports[port];
+
+	spin_lock(&ap->host->lock);
+	ahci_port_intr(ap);
+	spin_unlock(&ap->host->lock);
+
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
@@ -2220,6 +2234,80 @@ static void ahci_p5wdh_workaround(struct ata_host *host)
 	}
 }
 
+static int ahci_request_irq(struct pci_dev *pdev, struct ata_host *host,
+							int n_irqs)
+{
+	int rc;
+
+	if (n_irqs) {
+		rc = pci_enable_msi_block(pdev, n_irqs);
+		if (rc)
+			return rc;
+	}
+
+	if (n_irqs > 1) {
+		void __iomem *mmio = host->iomap[AHCI_PCI_BAR];
+		u32 host_ctl = readl(mmio + HOST_CTL);
+		if (host_ctl & HOST_MSI_RSM)
+			goto try_different;
+		rc = devm_request_irq(host->dev, pdev->irq, ahci_msi_interrupt,
+				IRQF_DISABLED,
+				dev_driver_string(host->dev), host);
+	} else {
+		rc = devm_request_irq(host->dev, pdev->irq, ahci_interrupt,
+				IRQF_SHARED,
+				dev_driver_string(host->dev), host);
+	}
+
+	if (!rc)
+		return 0;
+
+ try_different:
+	pci_disable_msi(pdev);
+	pci_intx(pdev, 1);
+	return (n_irqs == 1) ? rc : 1;
+}
+
+/*
+ * We only need one interrupt per port (plus one for CCC which isn't
+ * supported yet), but some AHCI controllers refuse to use multiple MSIs
+ * unless they get the maximum number of interrupts.  We don't support the
+ * mode where fewer interrupts are assigned than we have ports.
+ */
+static int ahci_setup_irqs(struct pci_dev *pdev, struct ata_host *host)
+{
+	struct ahci_host_priv *hpriv = host->private_data;
+	int n_irqs, pos, rc;
+	u16 control;
+
+	if (hpriv->flags & AHCI_HFLAG_NO_MSI)
+		goto no_msi;
+
+	rc = ahci_request_irq(pdev, host, host->n_ports);
+	if (rc == 0)
+		return 0;
+	if (rc < 0)
+		goto no_msi;
+
+	/* Find out how many it might want */
+	pos = pci_find_capability(pdev, PCI_CAP_ID_MSI);
+	pci_read_config_word(pdev, pos + PCI_MSI_FLAGS, &control);
+	n_irqs = 1 << ((control & PCI_MSI_FLAGS_QMASK) >> 1);
+
+	rc = ahci_request_irq(pdev, host, n_irqs);
+	if (rc == 0)
+		return 0;
+	if (rc < 0)
+		goto no_msi;
+
+	rc = ahci_request_irq(pdev, host, 1);
+	if (rc == 0)
+		return 0;
+
+ no_msi:
+	return ahci_request_irq(pdev, host, 0);
+}
+
 static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	static int printed_version;
@@ -2278,9 +2366,6 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	    (pdev->revision == 0xa1 || pdev->revision == 0xa2))
 		hpriv->flags |= AHCI_HFLAG_NO_MSI;
 
-	if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev))
-		pci_intx(pdev, 1);
-
 	/* save initial config */
 	ahci_save_initial_config(pdev, hpriv);
 
@@ -2335,8 +2420,17 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	ahci_print_info(host);
 
 	pci_set_master(pdev);
-	return ata_host_activate(host, pdev->irq, ahci_interrupt, IRQF_SHARED,
-				 &ahci_sht);
+
+	rc = ata_host_start(host);
+	if (rc)
+		return rc;
+
+	rc = ahci_setup_irqs(pdev, host);
+	if (rc)
+		return rc;
+
+	rc = ata_host_register(host, &ahci_sht);
+	return rc;
 }
 
 static int __init ahci_init(void)
-- 
1.5.5.4

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