s390/pci: Allow allocation of more than 1 MSI interrupt

On a PCI adapter that provides up to 8 MSI interrupt sources the s390
implementation of PCI interrupts rejected to accommodate them, although
the underlying hardware is able to support that.

For MSI-X it is sufficient to allocate a single irq_desc per msi_desc,
but for MSI multiple irq descriptors are attached to and controlled by
a single msi descriptor. Add the appropriate loops to maintain multiple
irq descriptors and tie/untie them to/from the appropriate AIBV bit, if
a device driver allocates more than 1 MSI interrupt.

Common PCI code passes on requests to allocate a number of interrupt
vectors based on the device drivers' demand and the PCI functions'
capabilities. However, the root-complex of s390 systems support just a
limited number of interrupt vectors per PCI function.
Produce a kernel log message to inform about any architecture-specific
capping that might be done.

With this change, we had a PCI adapter successfully raising
interrupts to its device driver via all 8 sources.

Fixes: a384c8924a8b ("s390/PCI: Fix single MSI only check")
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
index 979f776b09b8d9f25e0b457f93843e2c5f43d6ba..84482a92133220f446e30ae61b6af196aa17b4b4 100644 (file)
--- a/arch/s390/pci/pci_irq.c
+++ b/arch/s390/pci/pci_irq.c
@@ -298,8 +298,8 @@ static int __alloc_airq(struct zpci_dev *zdev, int msi_vecs,
 
 int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
 {
+       unsigned int hwirq, msi_vecs, irqs_per_msi, i, cpu;
        struct zpci_dev *zdev = to_zpci(pdev);
-       unsigned int hwirq, msi_vecs, cpu;
        struct msi_desc *msi;
        struct msi_msg msg;
        unsigned long bit;
@@ -309,30 +309,46 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
        zdev->aisb = -1UL;
        zdev->msi_first_bit = -1U;
 
-       if (type == PCI_CAP_ID_MSI && nvec > 1)
-               return 1;
        msi_vecs = min_t(unsigned int, nvec, zdev->max_msi);
+       if (msi_vecs < nvec) {
+               pr_info("%s requested %d irqs, allocate system limit of %d",
+                       pci_name(pdev), nvec, zdev->max_msi);
+       }
 
        rc = __alloc_airq(zdev, msi_vecs, &bit);
        if (rc < 0)
                return rc;
 
-       /* Request MSI interrupts */
+       /*
+        * Request MSI interrupts:
+        * When using MSI, nvec_used interrupt sources and their irq
+        * descriptors are controlled through one msi descriptor.
+        * Thus the outer loop over msi descriptors shall run only once,
+        * while two inner loops iterate over the interrupt vectors.
+        * When using MSI-X, each interrupt vector/irq descriptor
+        * is bound to exactly one msi descriptor (nvec_used is one).
+        * So the inner loops are executed once, while the outer iterates
+        * over the MSI-X descriptors.
+        */
        hwirq = bit;
        msi_for_each_desc(msi, &pdev->dev, MSI_DESC_NOTASSOCIATED) {
-               rc = -EIO;
                if (hwirq - bit >= msi_vecs)
                        break;
-               irq = __irq_alloc_descs(-1, 0, 1, 0, THIS_MODULE,
-                               (irq_delivery == DIRECTED) ?
-                               msi->affinity : NULL);
+               irqs_per_msi = min_t(unsigned int, msi_vecs, msi->nvec_used);
+               irq = __irq_alloc_descs(-1, 0, irqs_per_msi, 0, THIS_MODULE,
+                                       (irq_delivery == DIRECTED) ?
+                                       msi->affinity : NULL);
                if (irq < 0)
                        return -ENOMEM;
-               rc = irq_set_msi_desc(irq, msi);
-               if (rc)
-                       return rc;
-               irq_set_chip_and_handler(irq, &zpci_irq_chip,
-                                        handle_percpu_irq);
+
+               for (i = 0; i < irqs_per_msi; i++) {
+                       rc = irq_set_msi_desc_off(irq, i, msi);
+                       if (rc)
+                               return rc;
+                       irq_set_chip_and_handler(irq + i, &zpci_irq_chip,
+                                                handle_percpu_irq);
+               }
+
                msg.data = hwirq - bit;
                if (irq_delivery == DIRECTED) {
                        if (msi->affinity)
@@ -345,31 +361,35 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
                        msg.address_lo |= (cpu_addr << 8);
 
                        for_each_possible_cpu(cpu) {
-                               airq_iv_set_data(zpci_ibv[cpu], hwirq, irq);
+                               for (i = 0; i < irqs_per_msi; i++)
+                                       airq_iv_set_data(zpci_ibv[cpu],
+                                                        hwirq + i, irq + i);
                        }
                } else {
                        msg.address_lo = zdev->msi_addr & 0xffffffff;
-                       airq_iv_set_data(zdev->aibv, hwirq, irq);
+                       for (i = 0; i < irqs_per_msi; i++)
+                               airq_iv_set_data(zdev->aibv, hwirq + i, irq + i);
                }
                msg.address_hi = zdev->msi_addr >> 32;
                pci_write_msi_msg(irq, &msg);
-               hwirq++;
+               hwirq += irqs_per_msi;
        }
 
        zdev->msi_first_bit = bit;
-       zdev->msi_nr_irqs = msi_vecs;
+       zdev->msi_nr_irqs = hwirq - bit;
 
        rc = zpci_set_irq(zdev);
        if (rc)
                return rc;
 
-       return (msi_vecs == nvec) ? 0 : msi_vecs;
+       return (zdev->msi_nr_irqs == nvec) ? 0 : zdev->msi_nr_irqs;
 }
 
 void arch_teardown_msi_irqs(struct pci_dev *pdev)
 {
        struct zpci_dev *zdev = to_zpci(pdev);
        struct msi_desc *msi;
+       unsigned int i;
        int rc;
 
        /* Disable interrupts */
@@ -379,8 +399,10 @@ void arch_teardown_msi_irqs(struct pci_dev *pdev)
 
        /* Release MSI interrupts */
        msi_for_each_desc(msi, &pdev->dev, MSI_DESC_ASSOCIATED) {
-               irq_set_msi_desc(msi->irq, NULL);
-               irq_free_desc(msi->irq);
+               for (i = 0; i < msi->nvec_used; i++) {
+                       irq_set_msi_desc(msi->irq + i, NULL);
+                       irq_free_desc(msi->irq + i);
+               }
                msi->msg.address_lo = 0;
                msi->msg.address_hi = 0;
                msi->msg.data = 0;