[PATCH 7/7] irqchip/gic-v5: Defer default SPI and LPI IAFFID programming

[Lorenzo Pieralisi]

SPI and LPI interrupts do not have an architected default value for their
IAFFID (interrupt affinity ID) - the property that determines an IRQ
affinity.

Current code awkwardly tries to set a default IAFFID value corresponding
to the logical cpu executing the gicv5_hwirq_init() function at SPI/LPI
allocation time.

There are two issues with this approach:

- gicv5_hwirq_init() is called in preemptible context and current code
  uses smp_processor_id() to check the logical cpu executing the function.
  Whilst that's harmless, it can spit a splat on DEBUG_PREEMPT kernels
- Setting the default SPI/LPI IAFFID to the one belonging to the cpu
  executing the IRQ allocation is a completely arbitrary choice

It is saner to remove the SPI/LPI IAFFID set-up in the SPI/LPI domain IRQ
allocation code and flag SPI/LPI irqchips as IRQCHIP_AFFINITY_PRE_STARTUP
so that the SPI/LPI affinity is initialized by IRQ core to a sane value
before an IRQ is started up using the respective irq_chip
irq_set_affinity() callback.

Fixes: 5cb1b6dab2de ("irqchip/gic-v5: Add GICv5 IRS/SPI support")
Fixes: 0f0101325876 ("irqchip/gic-v5: Add GICv5 LPI/IPI support")
Signed-off-by: Lorenzo Pieralisi <lpieralisi at kernel.org>
Cc: Thomas Gleixner <tglx at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
---
 drivers/irqchip/irq-gic-v5.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
index 4f5d1eebb4fa..d6f1c0c8b747 100644
--- a/drivers/irqchip/irq-gic-v5.c
+++ b/drivers/irqchip/irq-gic-v5.c
@@ -87,25 +87,13 @@ static void gicv5_ppi_priority_init(void)
 
 static void gicv5_hwirq_init(irq_hw_number_t hwirq, u8 priority, u8 hwirq_type)
 {
-	u64 cdpri, cdaff;
-	u16 iaffid;
-	int ret;
+	u64 cdpri;
 
 	if (hwirq_type == GICV5_HWIRQ_TYPE_LPI || hwirq_type == GICV5_HWIRQ_TYPE_SPI) {
 		cdpri = FIELD_PREP(GICV5_GIC_CDPRI_PRIORITY_MASK, priority)	|
 			FIELD_PREP(GICV5_GIC_CDPRI_TYPE_MASK, hwirq_type)	|
 			FIELD_PREP(GICV5_GIC_CDPRI_ID_MASK, hwirq);
 		gic_insn(cdpri, CDPRI);
-
-		ret = gicv5_irs_cpu_to_iaffid(smp_processor_id(), &iaffid);
-
-		if (WARN_ON_ONCE(ret))
-			return;
-
-		cdaff = FIELD_PREP(GICV5_GIC_CDAFF_IAFFID_MASK, iaffid)		|
-			FIELD_PREP(GICV5_GIC_CDAFF_TYPE_MASK, hwirq_type)	|
-			FIELD_PREP(GICV5_GIC_CDAFF_ID_MASK, hwirq);
-		gic_insn(cdaff, CDAFF);
 	}
 }
 
@@ -548,6 +536,7 @@ static const struct irq_chip gicv5_spi_irq_chip = {
 	.irq_get_irqchip_state	= gicv5_spi_irq_get_irqchip_state,
 	.irq_set_irqchip_state	= gicv5_spi_irq_set_irqchip_state,
 	.flags			= IRQCHIP_SET_TYPE_MASKED |
+				  IRQCHIP_AFFINITY_PRE_STARTUP |
 				  IRQCHIP_SKIP_SET_WAKE	  |
 				  IRQCHIP_MASK_ON_SUSPEND,
 };
@@ -561,7 +550,8 @@ static const struct irq_chip gicv5_lpi_irq_chip = {
 	.irq_retrigger		= gicv5_lpi_irq_retrigger,
 	.irq_get_irqchip_state	= gicv5_lpi_irq_get_irqchip_state,
 	.irq_set_irqchip_state	= gicv5_lpi_irq_set_irqchip_state,
-	.flags			= IRQCHIP_SKIP_SET_WAKE	  |
+	.flags			= IRQCHIP_AFFINITY_PRE_STARTUP |
+				  IRQCHIP_SKIP_SET_WAKE	  |
 				  IRQCHIP_MASK_ON_SUSPEND,
 };
 

-- 
2.53.0