[PATCH] PCI: dwc: Move interrupt acking into the proper callback

[Niklas Cassel <niklas.cassel@linaro.org>]

From: Marc Zyngier <marc.zyngier@arm.com>

The write to the status register is really an ACK for the HW,
and should be treated as such by the driver. Let's move it to the
irq_ack() callback, which will prevent people from moving it around
in order to paper over other bugs.

Fixes: 8c934095fa2f ("PCI: dwc: Clear MSI interrupt status after it is handled,
not before")
Fixes: 7c5925afbc58 ("PCI: dwc: Move MSI IRQs allocation to IRQ domains
hierarchical API")
Link: https://lore.kernel.org/linux-pci/20181113225734.8026-1-marc.zyngier@arm.com/
Reported-by: Trent Piepho <tpiepho@impinj.com>
Tested-by: Niklas Cassel <niklas.cassel@linaro.org>
Tested-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Tested-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org
---
Original upstream commit SHA1: 3f7bb2ec20ce07c02b2002349d256c91a463fcc5

Sending a backport (which is authored by Marc, just like the original
commit), for 4.14-stable, since the original commit failed to apply there.

Not sure if Tested-by tags should remain.
Mine can be kept, since I've tested the backport.

 drivers/pci/dwc/pcie-designware-host.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
index bc3e2d8d0cce..58b38c54a7cf 100644
--- a/drivers/pci/dwc/pcie-designware-host.c
+++ b/drivers/pci/dwc/pcie-designware-host.c
@@ -45,8 +45,19 @@ static int dw_pcie_wr_own_conf(struct pcie_port *pp, int where, int size,
 	return dw_pcie_write(pci->dbi_base + where, size, val);
 }
 
+static void dwc_irq_ack(struct irq_data *d)
+{
+	struct msi_desc *msi = irq_data_get_msi_desc(d);
+	struct pcie_port *pp = msi_desc_to_pci_sysdata(msi);
+	int pos = d->hwirq % 32;
+	int i = d->hwirq / 32;
+
+	dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12, 4, BIT(pos));
+}
+
 static struct irq_chip dw_msi_irq_chip = {
 	.name = "PCI-MSI",
+	.irq_ack = dwc_irq_ack,
 	.irq_enable = pci_msi_unmask_irq,
 	.irq_disable = pci_msi_mask_irq,
 	.irq_mask = pci_msi_mask_irq,
@@ -72,8 +83,6 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
 					    pos)) != 32) {
 			irq = irq_find_mapping(pp->irq_domain, i * 32 + pos);
 			generic_handle_irq(irq);
-			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12,
-					    4, 1 << pos);
 			pos++;
 		}
 	}
@@ -263,7 +272,7 @@ static struct msi_controller dw_pcie_msi_chip = {
 static int dw_pcie_msi_map(struct irq_domain *domain, unsigned int irq,
 			   irq_hw_number_t hwirq)
 {
-	irq_set_chip_and_handler(irq, &dw_msi_irq_chip, handle_simple_irq);
+	irq_set_chip_and_handler(irq, &dw_msi_irq_chip, handle_edge_irq);
 	irq_set_chip_data(irq, domain->host_data);
 
 	return 0;
-- 
2.20.1