irqdomain: Allow quiet failure mode

Some interrupt controllers refuse to map interrupts marked as
"protected" by firwmare. Since we try to map everyting in the
device-tree on some platforms, we end up with a lot of nasty
WARN's in the boot log for what is a normal situation on those
machines.

This defines a specific return code (-EPERM) from the host map()
callback which cause irqdomain to fail silently.

MPIC is updated to return this when hitting a protected source
printing only a single line message for diagnostic purposes.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 17 insertions, 3 deletions

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 96f3a1d9c379..5a83dde8ca0c 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -462,9 +462,23 @@ int irq_domain_associate_many(struct irq_domain *domain, unsigned int irq_base,
                 if (domain->ops->map) {
                         ret = domain->ops->map(domain, virq, hwirq);
                         if (ret != 0) {
-                                pr_err("irq-%i==>hwirq-0x%lx mapping failed: %d\n",
-                                       virq, hwirq, ret);
-                                WARN_ON(1);
+                                /*
+                                 * If map() returns -EPERM, this interrupt is protected
+                                 * by the firmware or some other service and shall not
+                                 * be mapped.
+                                 *
+                                 * Since on some platforms we blindly try to map everything
+                                 * we end up with a log full of backtraces.
+                                 *
+                                 * So instead, we silently fail on -EPERM, it is the
+                                 * responsibility of the PIC driver to display a relevant
+                                 * message if needed.
+                                 */
+                                if (ret != -EPERM) {
+                                        pr_err("irq-%i==>hwirq-0x%lx mapping failed: %d\n",
+                                               virq, hwirq, ret);
+                                        WARN_ON(1);
+                                }
                                 irq_data->domain = NULL;
                                 irq_data->hwirq = 0;
                                 goto err_unmap;