AHCI: Support multiple MSIs

Take advantage of multiple MSIs implementation on x86 - on
systems with IRQ remapping AHCI ports not only get assigned
separate MSI vectors - but also separate IRQs. As result,
interrupts generated by different ports could be serviced on
different CPUs rather than on a single one.

In cases when number of allocated MSIs is less than requested
the Sharing Last MSI mode does not get used, no matter
implemented in hardware or not. Instead, the driver assumes the
advantage of multiple MSIs is negated and falls back to the
single MSI mode as if MRSM bit was set (some Intel chips
implement this strategy anyway - MRSM bit gets set even if the
number of allocated MSIs exceeds the number of implemented ports).

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Acked-by: Jeff Garzik <jgarzik@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/15bf7ee314dd55f21ec7d2a01c47613cd8190a7c.1353324359.git.agordeev@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 89 insertions, 4 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 497912732566..495aeed26779 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1061,6 +1061,86 @@ static inline void ahci_gtf_filter_workaround(struct ata_host *host)
 {}
 #endif
 
+int ahci_init_interrupts(struct pci_dev *pdev, struct ahci_host_priv *hpriv)
+{
+        int rc;
+        unsigned int maxvec;
+
+        if (!(hpriv->flags & AHCI_HFLAG_NO_MSI)) {
+                rc = pci_enable_msi_block_auto(pdev, &maxvec);
+                if (rc > 0) {
+                        if ((rc == maxvec) || (rc == 1))
+                                return rc;
+                        /*
+                         * Assume that advantage of multipe MSIs is negated,
+                         * so fallback to single MSI mode to save resources
+                         */
+                        pci_disable_msi(pdev);
+                        if (!pci_enable_msi(pdev))
+                                return 1;
+                }
+        }
+
+        pci_intx(pdev, 1);
+        return 0;
+}
+
+/**
+ *      ahci_host_activate - start AHCI host, request IRQs and register it
+ *      @host: target ATA host
+ *      @irq: base IRQ number to request
+ *      @n_msis: number of MSIs allocated for this host
+ *      @irq_handler: irq_handler used when requesting IRQs
+ *      @irq_flags: irq_flags used when requesting IRQs
+ *
+ *      Similar to ata_host_activate, but requests IRQs according to AHCI-1.1
+ *      when multiple MSIs were allocated. That is one MSI per port, starting
+ *      from @irq.
+ *
+ *      LOCKING:
+ *      Inherited from calling layer (may sleep).
+ *
+ *      RETURNS:
+ *      0 on success, -errno otherwise.
+ */
+int ahci_host_activate(struct ata_host *host, int irq, unsigned int n_msis)
+{
+        int i, rc;
+
+        /* Sharing Last Message among several ports is not supported */
+        if (n_msis < host->n_ports)
+                return -EINVAL;
+
+        rc = ata_host_start(host);
+        if (rc)
+                return rc;
+
+        for (i = 0; i < host->n_ports; i++) {
+                rc = devm_request_threaded_irq(host->dev,
+                        irq + i, ahci_hw_interrupt, ahci_thread_fn, IRQF_SHARED,
+                        dev_driver_string(host->dev), host->ports[i]);
+                if (rc)
+                        goto out_free_irqs;
+        }
+
+        for (i = 0; i < host->n_ports; i++)
+                ata_port_desc(host->ports[i], "irq %d", irq + i);
+
+        rc = ata_host_register(host, &ahci_sht);
+        if (rc)
+                goto out_free_all_irqs;
+
+        return 0;
+
+out_free_all_irqs:
+        i = host->n_ports;
+out_free_irqs:
+        for (i--; i >= 0; i--)
+                devm_free_irq(host->dev, irq + i, host->ports[i]);
+
+        return rc;
+}
+
 static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
         unsigned int board_id = ent->driver_data;
@@ -1069,7 +1149,7 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
         struct device *dev = &pdev->dev;
         struct ahci_host_priv *hpriv;
         struct ata_host *host;
-        int n_ports, i, rc;
+        int n_ports, n_msis, i, rc;
         int ahci_pci_bar = AHCI_PCI_BAR_STANDARD;
 
         VPRINTK("ENTER\n");
@@ -1156,11 +1236,12 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
         if (ahci_sb600_enable_64bit(pdev))
                 hpriv->flags &= ~AHCI_HFLAG_32BIT_ONLY;
 
-        if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev))
-                pci_intx(pdev, 1);
-
         hpriv->mmio = pcim_iomap_table(pdev)[ahci_pci_bar];
 
+        n_msis = ahci_init_interrupts(pdev, hpriv);
+        if (n_msis > 1)
+                hpriv->flags |= AHCI_HFLAG_MULTI_MSI;
+
         /* save initial config */
         ahci_pci_save_initial_config(pdev, hpriv);
 
@@ -1256,6 +1337,10 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
         ahci_pci_print_info(host);
 
         pci_set_master(pdev);
+
+        if (hpriv->flags & AHCI_HFLAG_MULTI_MSI)
+                return ahci_host_activate(host, pdev->irq, n_msis);
+
         return ata_host_activate(host, pdev->irq, ahci_interrupt, IRQF_SHARED,
                                  &ahci_sht);
 }