IRQCHIP: mips-gic: Avoid rerouting timer IRQs for smp-cmp

Commit e9de688dac65 ("irqchip: mips-gic: Support local interrupts")
changed the GIC irqchip driver so that all local interrupts were routed
to the same CPU pin used for external interrupts. Unfortunately this
causes a regression when smp-cmp is used. The CPUs are started by the
bootloader and put in a timer based waiting poll loop, but when their
timer interrupts are rerouted to a different IRQ pin which is not
unmasked they never wake up.

Since smp-cmp support is deprecated and everybody who was using it
should be switching to smp-cps which brings up the secondary CPUs
without bootloader assistance, I've gone for the simple fix which can be
easily removed once smp-cmp is removed, rather than a fully generic fix.

In __gic_init() the local GIC_VPE_TIMER_MAP register is read to find the
boot-time routing of the local timer interrupt, and a chained handler is
added to that CPU pin as well as the normal one.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Fixes: e9de688dac65 ("irqchip: mips-gic: Support local interrupts")
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Patchwork: https://patchwork.linux-mips.org/patch/9081/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 2b0468e3df6a..56b96c63dc4b 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -37,6 +37,7 @@ static struct irq_domain *gic_irq_domain;
 static int gic_shared_intrs;
 static int gic_vpes;
 static unsigned int gic_cpu_pin;
+static unsigned int timer_cpu_pin;
 static struct irq_chip gic_level_irq_controller, gic_edge_irq_controller;
 
 static void __gic_irq_dispatch(void);
@@ -616,6 +617,8 @@ static int gic_local_irq_domain_map(struct irq_domain *d, unsigned int virq,
                         gic_write(GIC_REG(VPE_OTHER, GIC_VPE_COMPARE_MAP), val);
                         break;
                 case GIC_LOCAL_INT_TIMER:
+                        /* CONFIG_MIPS_CMP workaround (see __gic_init) */
+                        val = GIC_MAP_TO_PIN_MSK | timer_cpu_pin;
                         gic_write(GIC_REG(VPE_OTHER, GIC_VPE_TIMER_MAP), val);
                         break;
                 case GIC_LOCAL_INT_PERFCTR:
@@ -713,12 +716,36 @@ static void __init __gic_init(unsigned long gic_base_addr,
         if (cpu_has_veic) {
                 /* Always use vector 1 in EIC mode */
                 gic_cpu_pin = 0;
+                timer_cpu_pin = gic_cpu_pin;
                 set_vi_handler(gic_cpu_pin + GIC_PIN_TO_VEC_OFFSET,
                                __gic_irq_dispatch);
         } else {
                 gic_cpu_pin = cpu_vec - GIC_CPU_PIN_OFFSET;
                 irq_set_chained_handler(MIPS_CPU_IRQ_BASE + cpu_vec,
                                         gic_irq_dispatch);
+                /*
+                 * With the CMP implementation of SMP (deprecated), other CPUs
+                 * are started by the bootloader and put into a timer based
+                 * waiting poll loop. We must not re-route those CPU's local
+                 * timer interrupts as the wait instruction will never finish,
+                 * so just handle whatever CPU interrupt it is routed to by
+                 * default.
+                 *
+                 * This workaround should be removed when CMP support is
+                 * dropped.
+                 */
+                if (IS_ENABLED(CONFIG_MIPS_CMP) &&
+                    gic_local_irq_is_routable(GIC_LOCAL_INT_TIMER)) {
+                        timer_cpu_pin = gic_read(GIC_REG(VPE_LOCAL,
+                                                         GIC_VPE_TIMER_MAP)) &
+                                        GIC_MAP_MSK;
+                        irq_set_chained_handler(MIPS_CPU_IRQ_BASE +
+                                                GIC_CPU_PIN_OFFSET +
+                                                timer_cpu_pin,
+                                                gic_irq_dispatch);
+                } else {
+                        timer_cpu_pin = gic_cpu_pin;
+                }
         }
 
         gic_irq_domain = irq_domain_add_simple(node, GIC_NUM_LOCAL_INTRS +