[openwrt/openwrt] kernel: backport a fix for a regression that broke IRQ affinity on ARM

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/9c5128854eaf44395ab09e423fe7e36e7acfd241

commit 9c5128854eaf44395ab09e423fe7e36e7acfd241
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Aug 21 20:44:25 2020 +0200

    kernel: backport a fix for a regression that broke IRQ affinity on ARM
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 ...nity-Make-affinity-setting-if-activated-o.patch | 129 +++++++++++++++++++++
 1 file changed, 129 insertions(+)

diff --git a/target/linux/generic/backport-5.4/041-genirq-affinity-Make-affinity-setting-if-activated-o.patch b/target/linux/generic/backport-5.4/041-genirq-affinity-Make-affinity-setting-if-activated-o.patch
new file mode 100644
index 0000000000..cf4f6e1e21
--- /dev/null
+++ b/target/linux/generic/backport-5.4/041-genirq-affinity-Make-affinity-setting-if-activated-o.patch
@@ -0,0 +1,129 @@
+From: Thomas Gleixner <tglx at linutronix.de>
+Date: Fri, 24 Jul 2020 22:44:41 +0200
+Subject: [PATCH] genirq/affinity: Make affinity setting if activated opt-in
+
+commit f0c7baca180046824e07fc5f1326e83a8fd150c7 upstream.
+
+John reported that on a RK3288 system the perf per CPU interrupts are all
+affine to CPU0 and provided the analysis:
+
+ "It looks like what happens is that because the interrupts are not per-CPU
+  in the hardware, armpmu_request_irq() calls irq_force_affinity() while
+  the interrupt is deactivated and then request_irq() with IRQF_PERCPU |
+  IRQF_NOBALANCING.
+
+  Now when irq_startup() runs with IRQ_STARTUP_NORMAL, it calls
+  irq_setup_affinity() which returns early because IRQF_PERCPU and
+  IRQF_NOBALANCING are set, leaving the interrupt on its original CPU."
+
+This was broken by the recent commit which blocked interrupt affinity
+setting in hardware before activation of the interrupt. While this works in
+general, it does not work for this particular case. As contrary to the
+initial analysis not all interrupt chip drivers implement an activate
+callback, the safe cure is to make the deferred interrupt affinity setting
+at activation time opt-in.
+
+Implement the necessary core logic and make the two irqchip implementations
+for which this is required opt-in. In hindsight this would have been the
+right thing to do, but ...
+
+Fixes: baedb87d1b53 ("genirq/affinity: Handle affinity setting on inactive interrupts correctly")
+Reported-by: John Keeping <john at metanate.com>
+Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
+Tested-by: Marc Zyngier <maz at kernel.org>
+Acked-by: Marc Zyngier <maz at kernel.org>
+Cc: stable at vger.kernel.org
+Link: https://lkml.kernel.org/r/87blk4tzgm.fsf@nanos.tec.linutronix.de
+Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
+---
+
+--- a/arch/x86/kernel/apic/vector.c
++++ b/arch/x86/kernel/apic/vector.c
+@@ -554,6 +554,10 @@ static int x86_vector_alloc_irqs(struct
+ 		irqd->chip_data = apicd;
+ 		irqd->hwirq = virq + i;
+ 		irqd_set_single_target(irqd);
++
++		/* Don't invoke affinity setter on deactivated interrupts */
++		irqd_set_affinity_on_activate(irqd);
++
+ 		/*
+ 		 * Legacy vectors are already assigned when the IOAPIC
+ 		 * takes them over. They stay on the same vector. This is
+--- a/drivers/irqchip/irq-gic-v3-its.c
++++ b/drivers/irqchip/irq-gic-v3-its.c
+@@ -2581,6 +2581,7 @@ static int its_irq_domain_alloc(struct i
+ 	msi_alloc_info_t *info = args;
+ 	struct its_device *its_dev = info->scratchpad[0].ptr;
+ 	struct its_node *its = its_dev->its;
++	struct irq_data *irqd;
+ 	irq_hw_number_t hwirq;
+ 	int err;
+ 	int i;
+@@ -2600,7 +2601,9 @@ static int its_irq_domain_alloc(struct i
+ 
+ 		irq_domain_set_hwirq_and_chip(domain, virq + i,
+ 					      hwirq + i, &its_irq_chip, its_dev);
+-		irqd_set_single_target(irq_desc_get_irq_data(irq_to_desc(virq + i)));
++		irqd = irq_get_irq_data(virq + i);
++		irqd_set_single_target(irqd);
++		irqd_set_affinity_on_activate(irqd);
+ 		pr_debug("ID:%d pID:%d vID:%d\n",
+ 			 (int)(hwirq + i - its_dev->event_map.lpi_base),
+ 			 (int)(hwirq + i), virq + i);
+--- a/include/linux/irq.h
++++ b/include/linux/irq.h
+@@ -211,6 +211,8 @@ struct irq_data {
+  * IRQD_CAN_RESERVE		- Can use reservation mode
+  * IRQD_MSI_NOMASK_QUIRK	- Non-maskable MSI quirk for affinity change
+  *				  required
++ * IRQD_AFFINITY_ON_ACTIVATE	- Affinity is set on activation. Don't call
++ *				  irq_chip::irq_set_affinity() when deactivated.
+  */
+ enum {
+ 	IRQD_TRIGGER_MASK		= 0xf,
+@@ -234,6 +236,7 @@ enum {
+ 	IRQD_DEFAULT_TRIGGER_SET	= (1 << 25),
+ 	IRQD_CAN_RESERVE		= (1 << 26),
+ 	IRQD_MSI_NOMASK_QUIRK		= (1 << 27),
++	IRQD_AFFINITY_ON_ACTIVATE	= (1 << 29),
+ };
+ 
+ #define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, state_use_accessors)
+@@ -408,6 +411,16 @@ static inline bool irqd_msi_nomask_quirk
+ 	return __irqd_to_state(d) & IRQD_MSI_NOMASK_QUIRK;
+ }
+ 
++static inline void irqd_set_affinity_on_activate(struct irq_data *d)
++{
++	__irqd_to_state(d) |= IRQD_AFFINITY_ON_ACTIVATE;
++}
++
++static inline bool irqd_affinity_on_activate(struct irq_data *d)
++{
++	return __irqd_to_state(d) & IRQD_AFFINITY_ON_ACTIVATE;
++}
++
+ #undef __irqd_to_state
+ 
+ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
+--- a/kernel/irq/manage.c
++++ b/kernel/irq/manage.c
+@@ -281,12 +281,16 @@ static bool irq_set_affinity_deactivated
+ 	struct irq_desc *desc = irq_data_to_desc(data);
+ 
+ 	/*
++	 * Handle irq chips which can handle affinity only in activated
++	 * state correctly
++	 *
+ 	 * If the interrupt is not yet activated, just store the affinity
+ 	 * mask and do not call the chip driver at all. On activation the
+ 	 * driver has to make sure anyway that the interrupt is in a
+ 	 * useable state so startup works.
+ 	 */
+-	if (!IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) || irqd_is_activated(data))
++	if (!IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) ||
++	    irqd_is_activated(data) || !irqd_affinity_on_activate(data))
+ 		return false;
+ 
+ 	cpumask_copy(desc->irq_common_data.affinity, mask);