linux-kernel - [PATCH 3/4] AHCI: Request multiple MSIs

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Date:	Sat,  5 Jul 2008 09:34:14 -0400
From:	Matthew Wilcox <matthew@....cx>
To:	linux-pci@...r.kernel.org
Cc:	kaneshige.kenji@...fujitsu.com, mingo@...e.hu, tglx@...utronix.de,
	davem@...emloft.net, dan.j.williams@...el.com,
	Martine.Silbermann@...com, benh@...nel.crashing.org,
	michael@...erman.id.au, linux-kernel@...r.kernel.org,
	Matthew Wilcox <matthew@....cx>,
	Matthew Wilcox <willy@...ux.intel.com>
Subject: [PATCH 3/4] AHCI: Request multiple MSIs

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@...ux.intel.com>
---
 drivers/ata/ahci.c |   84 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 79 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 061817a..4b2f90a 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 +1772,13 @@ static void ahci_port_intr(struct ata_port *ap)
 	}
 }
 
+static irqreturn_t ahci_msi_interrupt(int irq, void *dev_instance)
+{
+	struct ata_port *ap = dev_instance;
+	ahci_port_intr(ap);
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
 {
 	struct ata_host *host = dev_instance;
@@ -2210,6 +2218,66 @@ static void ahci_p5wdh_workaround(struct ata_host *host)
 	}
 }
 
+static int ahci_request_irqs(struct pci_dev *pdev, struct ata_host *host)
+{
+	int i, n_irqs, rc;
+	struct ahci_host_priv *hpriv = host->private_data;
+
+	if (hpriv->flags & AHCI_HFLAG_NO_MSI) {
+		n_irqs = 1;
+	} else {
+		u16 control;
+		int 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);
+
+		for (;;) {
+			rc = pci_enable_msi_block(pdev, n_irqs);
+			if (rc == 0) {
+				void __iomem *mmio = host->iomap[AHCI_PCI_BAR];
+				u32 host_ctl = readl(mmio + HOST_CTL);
+				if ((host_ctl & HOST_MSI_RSM) == 0)
+					break;
+				pci_disable_msi(pdev);
+				n_irqs = 1;
+			} else if (rc < 0) {
+				n_irqs = 1;
+				pci_intx(pdev, 1);
+				break;
+			} else {
+				n_irqs = rc;
+			}
+		}
+	}
+
+	/* FIXME: Add support for CCC */
+	if (n_irqs > host->n_ports) {
+		n_irqs = host->n_ports;
+	} else if (n_irqs < host->n_ports) {
+		n_irqs--;
+		rc = devm_request_irq(host->dev, pdev->irq + n_irqs,
+				ahci_interrupt, IRQF_SHARED,
+				dev_driver_string(host->dev), host);
+		if (rc)
+			goto release_block;
+	}
+
+	for (i = 0; i < n_irqs; i++) {
+		rc = devm_request_irq(host->dev, pdev->irq + i,
+				ahci_msi_interrupt, IRQF_SHARED,
+				dev_driver_string(host->dev), host->ports[i]);
+		if (rc)
+			goto release_block;
+	}
+
+	return 0;
+
+ release_block:
+	pci_disable_msi(pdev);
+	pci_intx(pdev, 1);
+	return rc;
+}
+
 static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	static int printed_version;
@@ -2268,9 +2336,6 @@ 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);
 
@@ -2325,8 +2390,17 @@ 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_request_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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