ata: ahci: simplify init function

This patch moves all the IRQ vector allocations into a single
function. Instead of having the allocations spread out over
two separate call sites everything will be handled in ahci_init_irq.
Also a direct call into pci(m)_intx will be removed.

The main part of this change is done by adding a PCI_IRQ_INTX flag into
an already existing pci_alloc_irq_vectors invocation.
In the current implementation of the pci_alloc_irq_vectors is the sequence
of calls msi-x -> msi -> legacy irq and whatever there succeeds stops the
call chain. That makes it impossible to merge all instances into as
a single call to pci_alloc_irq_vectors since the order of calls there is:
multiple msi-x
a single msi
a single msi-x
a legacy irq.
The two last steps can be merged into a single one which are
the msi-x and legacy irq option.

When PCI_IRQ_INTX flag is set the pci_alloc_irq_vectors succeeds in almost
all cases - that makes it possible to convert ahci_init_irq(msi) into
a void function. The exception is when dev->irq is zero then the
pci_alloc_irq_vectors may return with an error code also pci_intx isn't
called from  pci_alloc_irq_vectors and thus certain pci calls aren't
performed.
That's just a negligible issue as later in ahci_init_one the (zero)
value of dev->irq is via pci_irq_vector assigned to hpriv->irq.
That value is then later tested in ahci_host_activate->ata_host_activate
where it is welcomed with a WARN_ON message and fails with setting up
irq and then the probe function (ahci_init_one) fails.
The special zero value's meaning is that polling mode is being be set
up which isn't the case.

No functional change.

Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Link: https://lore.kernel.org/r/20250319155030.16410-1-thenzl@redhat.com
Signed-off-by: Niklas Cassel <cassel@kernel.org>

drivers/ata/ahci.c

@@ -1676,13 +1676,15 @@ static int ahci_get_irq_vector(struct ata_host *host, int port)
 	return pci_irq_vector(to_pci_dev(host->dev), port);
 }
 
-static int ahci_init_msi(struct pci_dev *pdev, unsigned int n_ports,
+static void ahci_init_irq(struct pci_dev *pdev, unsigned int n_ports,
 			struct ahci_host_priv *hpriv)
 {
 	int nvec;
 
-	if (hpriv->flags & AHCI_HFLAG_NO_MSI)
-		return -ENODEV;
+	if (hpriv->flags & AHCI_HFLAG_NO_MSI) {
+		pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_INTX);
+		return;
+	}
 
 	/*
 	 * If number of MSIs is less than number of ports then Sharing Last
@@ -1696,7 +1698,7 @@ static int ahci_init_msi(struct pci_dev *pdev, unsigned int n_ports,
 			if (!(readl(hpriv->mmio + HOST_CTL) & HOST_MRSM)) {
 				hpriv->get_irq_vector = ahci_get_irq_vector;
 				hpriv->flags |= AHCI_HFLAG_MULTI_MSI;
-				return nvec;
+				return;
 			}
 
 			/*
@@ -1711,12 +1713,13 @@ static int ahci_init_msi(struct pci_dev *pdev, unsigned int n_ports,
 
 	/*
 	 * If the host is not capable of supporting per-port vectors, fall
-	 * back to single MSI before finally attempting single MSI-X.
+	 * back to single MSI before finally attempting single MSI-X or
+	 * a legacy INTx.
 	 */
 	nvec = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSI);
 	if (nvec == 1)
-		return nvec;
-	return pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSIX);
+		return;
+	pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSIX | PCI_IRQ_INTX);
 }
 
 static void ahci_mark_external_port(struct ata_port *ap)
@@ -1996,10 +1999,8 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	}
 	host->private_data = hpriv;
 
-	if (ahci_init_msi(pdev, n_ports, hpriv) < 0) {
-		/* legacy intx interrupts */
-		pcim_intx(pdev, 1);
-	}
+	ahci_init_irq(pdev, n_ports, hpriv);
+
 	hpriv->irq = pci_irq_vector(pdev, 0);
 
 	if (!(hpriv->cap & HOST_CAP_SSS) || ahci_ignore_sss)