PCI: designware: Setup and clear exactly one MSI at a time

The setup_irq function is supposed to set up exactly one MSI IRQ.  Multiple
IRQ setup is handled differently, to respect the choices made by the upper
layers.

Also only clear one MSI IRQ at a time; the PCI core will call into this
function multiple times if it has to tear down more than one MSI IRQ.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pratyush Anand <pratyush.anand@st.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>

drivers/pci/host/pcie-designware.c

@@ -313,54 +313,17 @@ static int assign_irq(int no_irqs, struct msi_desc *desc, int *pos)
 	return -ENOSPC;
 }
 
-static void clear_irq(unsigned int irq)
-{
-	unsigned int pos, nvec;
-	struct msi_desc *msi;
-	struct pcie_port *pp;
-	struct irq_data *data = irq_get_irq_data(irq);
-
-	/* get the port structure */
-	msi = irq_data_get_msi(data);
-	pp = sys_to_pcie(msi->dev->bus->sysdata);
-
-	/* undo what was done in assign_irq */
-	pos = data->hwirq;
-	nvec = 1 << msi->msi_attrib.multiple;
-
-	clear_irq_range(pp, irq, nvec, pos);
-
-	/* all irqs cleared; reset attributes */
-	msi->irq = 0;
-	msi->msi_attrib.multiple = 0;
-}
-
 static int dw_msi_setup_irq(struct msi_chip *chip, struct pci_dev *pdev,
 			struct msi_desc *desc)
 {
-	int irq, pos, msgvec;
-	u16 msg_ctr;
+	int irq, pos;
 	struct msi_msg msg;
 	struct pcie_port *pp = sys_to_pcie(pdev->bus->sysdata);
 
-	pci_read_config_word(pdev, desc->msi_attrib.pos+PCI_MSI_FLAGS,
-				&msg_ctr);
-	msgvec = (msg_ctr&PCI_MSI_FLAGS_QSIZE) >> 4;
-	if (msgvec == 0)
-		msgvec = (msg_ctr & PCI_MSI_FLAGS_QMASK) >> 1;
-	if (msgvec > 5)
-		msgvec = 0;
-
-	irq = assign_irq((1 << msgvec), desc, &pos);
+	irq = assign_irq(1, desc, &pos);
 	if (irq < 0)
 		return irq;
 
-	/*
-	 * write_msi_msg() will update PCI_MSI_FLAGS so there is
-	 * no need to explicitly call pci_write_config_word().
-	 */
-	desc->msi_attrib.multiple = msgvec;
-
 	if (pp->ops->get_msi_addr)
 		msg.address_lo = pp->ops->get_msi_addr(pp);
 	else
@@ -379,7 +342,11 @@ static int dw_msi_setup_irq(struct msi_chip *chip, struct pci_dev *pdev,
 
 static void dw_msi_teardown_irq(struct msi_chip *chip, unsigned int irq)
 {
-	clear_irq(irq);
+	struct irq_data *data = irq_get_irq_data(irq);
+	struct msi_desc *msi = irq_data_get_msi(data);
+	struct pcie_port *pp = sys_to_pcie(msi->dev->bus->sysdata);
+
+	clear_irq_range(pp, irq, 1, data->hwirq);
 }
 
 static struct msi_chip dw_pcie_msi_chip = {