[PATCH v3 0/2] Improve PLIC functionality

[PATCH v3 0/2] Improve PLIC functionality

[Atish Patra]

This series adds following PLIC functionalities

1. Enable/disable interrupts only on cpu online/offline events.
2. Support multiple PLIC nodes in the device tree. This is required
for multi-socket platforms such as OmniXtend.

The 1st patch was originally part of the CPU hotplug series[1]. It is added to
this series now to keep all the PLIC related changes together.

Rebased on top of 5.6-rc4.
 
[1] https://patchwork.kernel.org/patch/11407379/

Atish Patra (2):
irqchip/sifive-plic: Enable/Disable external interrupts upon cpu
online/offline
irqchip/sifive-plic: Add support for multiple PLICs

arch/riscv/kernel/traps.c         |   2 +-
drivers/irqchip/irq-sifive-plic.c | 119 +++++++++++++++++++++---------
include/linux/cpuhotplug.h        |   1 +
3 files changed, 87 insertions(+), 35 deletions(-)

--
2.25.0

[PATCH v3 1/2] irqchip/sifive-plic: Enable/Disable external interrupts upon cpu online/offline

[Atish Patra]

Currently, PLIC threshold is only initialized once in the beginning.
However, threshold can be set to disabled if a CPU is marked offline with
CPU hotplug feature. This will not allow to change the irq affinity to a
CPU that just came online.

Add PLIC specific CPU hotplug callbacks and enable the threshold when a CPU
comes online. Take this opportunity to move the external interrupt enable
code from trap init to PLIC driver as well. On cpu offline path, the driver
performs the exact opposite operations i.e. disable the interrupt and
the threshold.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/kernel/traps.c         |  2 +-
 drivers/irqchip/irq-sifive-plic.c | 38 +++++++++++++++++++++++++++----
 include/linux/cpuhotplug.h        |  1 +
 3 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index ffb3d94bf0cc..55ea614d89bf 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -157,5 +157,5 @@ void __init trap_init(void)
 	/* Set the exception vector address */
 	csr_write(CSR_TVEC, &handle_exception);
 	/* Enable interrupts */
-	csr_write(CSR_IE, IE_SIE | IE_EIE);
+	csr_write(CSR_IE, IE_SIE);
 }
diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index aa4af886e43a..7c7f37393f99 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2018 Christoph Hellwig
  */
 #define pr_fmt(fmt) "plic: " fmt
+#include <linux/cpu.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
@@ -55,6 +56,9 @@
 #define     CONTEXT_THRESHOLD		0x00
 #define     CONTEXT_CLAIM		0x04
 
+#define	PLIC_DISABLE_THRESHOLD		0xf
+#define	PLIC_ENABLE_THRESHOLD		0
+
 static void __iomem *plic_regs;
 
 struct plic_handler {
@@ -230,6 +234,32 @@ static int plic_find_hart_id(struct device_node *node)
 	return -1;
 }
 
+static void plic_set_threshold(struct plic_handler *handler, u32 threshold)
+{
+	/* priority must be > threshold to trigger an interrupt */
+	writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
+}
+
+static int plic_dying_cpu(unsigned int cpu)
+{
+	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
+
+	csr_clear(CSR_IE, IE_EIE);
+	plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
+
+	return 0;
+}
+
+static int plic_starting_cpu(unsigned int cpu)
+{
+	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
+
+	csr_set(CSR_IE, IE_EIE);
+	plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);
+
+	return 0;
+}
+
 static int __init plic_init(struct device_node *node,
 		struct device_node *parent)
 {
@@ -267,7 +297,6 @@ static int __init plic_init(struct device_node *node,
 		struct plic_handler *handler;
 		irq_hw_number_t hwirq;
 		int cpu, hartid;
-		u32 threshold = 0;
 
 		if (of_irq_parse_one(node, i, &parent)) {
 			pr_err("failed to parse parent for context %d.\n", i);
@@ -301,7 +330,7 @@ static int __init plic_init(struct device_node *node,
 		handler = per_cpu_ptr(&plic_handlers, cpu);
 		if (handler->present) {
 			pr_warn("handler already present for context %d.\n", i);
-			threshold = 0xffffffff;
+			plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
 			goto done;
 		}
 
@@ -313,13 +342,14 @@ static int __init plic_init(struct device_node *node,
 			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
 
 done:
-		/* priority must be > threshold to trigger an interrupt */
-		writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
 		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
 			plic_toggle(handler, hwirq, 0);
 		nr_handlers++;
 	}
 
+	cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
+				  "irqchip/sifive/plic:starting",
+				  plic_starting_cpu, plic_dying_cpu);
 	pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
 		nr_irqs, nr_handlers, nr_contexts);
 	set_handle_irq(plic_handle_irq);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index d37c17e68268..77d70b633531 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -102,6 +102,7 @@ enum cpuhp_state {
 	CPUHP_AP_IRQ_ARMADA_XP_STARTING,
 	CPUHP_AP_IRQ_BCM2836_STARTING,
 	CPUHP_AP_IRQ_MIPS_GIC_STARTING,
+	CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
 	CPUHP_AP_ARM_MVEBU_COHERENCY,
 	CPUHP_AP_MICROCODE_LOADER,
 	CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
-- 
2.25.0

Re: [PATCH v3 1/2] irqchip/sifive-plic: Enable/Disable external interrupts upon cpu online/offline

[Marc Zyngier]

On Mon,  2 Mar 2020 15:11:45 -0800
Atish Patra <atish.patra@wdc.com> wrote:

> Currently, PLIC threshold is only initialized once in the beginning.
> However, threshold can be set to disabled if a CPU is marked offline with
> CPU hotplug feature. This will not allow to change the irq affinity to a
> CPU that just came online.
> 
> Add PLIC specific CPU hotplug callbacks and enable the threshold when a CPU
> comes online. Take this opportunity to move the external interrupt enable
> code from trap init to PLIC driver as well. On cpu offline path, the driver
> performs the exact opposite operations i.e. disable the interrupt and
> the threshold.
> 
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Reviewed-by: Anup Patel <anup@brainfault.org>

Both patches queued for 5.7 (please add a cover letter when sending a
patch series).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH v3 1/2] irqchip/sifive-plic: Enable/Disable external interrupts upon cpu online/offline

[Marc Zyngier]

On Sun, 8 Mar 2020 13:59:31 +0000
Marc Zyngier <maz@kernel.org> wrote:

> On Mon,  2 Mar 2020 15:11:45 -0800
> Atish Patra <atish.patra@wdc.com> wrote:
> 
> > Currently, PLIC threshold is only initialized once in the beginning.
> > However, threshold can be set to disabled if a CPU is marked offline with
> > CPU hotplug feature. This will not allow to change the irq affinity to a
> > CPU that just came online.
> > 
> > Add PLIC specific CPU hotplug callbacks and enable the threshold when a CPU
> > comes online. Take this opportunity to move the external interrupt enable
> > code from trap init to PLIC driver as well. On cpu offline path, the driver
> > performs the exact opposite operations i.e. disable the interrupt and
> > the threshold.
> > 
> > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > Reviewed-by: Anup Patel <anup@brainfault.org>  
> 
> Both patches queued for 5.7 (please add a cover letter when sending a
> patch series).

Apologies, there was a cover letter. I just messed my filters... ;-)

	M.
-- 
Jazz is not dead. It just smells funny...

[PATCH v3 2/2] irqchip/sifive-plic: Add support for multiple PLICs

[Atish Patra]

Current, PLIC driver can support only 1 PLIC on the board. However,
there can be multiple PLICs present on a two socket systems in RISC-V.

Modify the driver so that each PLIC handler can have a information
about individual PLIC registers and an irqdomain associated with it.

Tested on two socket RISC-V system based on VCU118 FPGA connected via
OmniXtend protocol.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 drivers/irqchip/irq-sifive-plic.c | 81 +++++++++++++++++++------------
 1 file changed, 51 insertions(+), 30 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 7c7f37393f99..c34fb3ae0ff8 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -59,7 +59,11 @@
 #define	PLIC_DISABLE_THRESHOLD		0xf
 #define	PLIC_ENABLE_THRESHOLD		0
 
-static void __iomem *plic_regs;
+struct plic_priv {
+	struct cpumask lmask;
+	struct irq_domain *irqdomain;
+	void __iomem *regs;
+};
 
 struct plic_handler {
 	bool			present;
@@ -70,6 +74,7 @@ struct plic_handler {
 	 */
 	raw_spinlock_t		enable_lock;
 	void __iomem		*enable_base;
+	struct plic_priv	*priv;
 };
 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
 
@@ -88,31 +93,40 @@ static inline void plic_toggle(struct plic_handler *handler,
 }
 
 static inline void plic_irq_toggle(const struct cpumask *mask,
-				   int hwirq, int enable)
+				   struct irq_data *d, int enable)
 {
 	int cpu;
+	struct plic_priv *priv = irq_get_chip_data(d->irq);
 
-	writel(enable, plic_regs + PRIORITY_BASE + hwirq * PRIORITY_PER_ID);
+	writel(enable, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
 	for_each_cpu(cpu, mask) {
 		struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
 
-		if (handler->present)
-			plic_toggle(handler, hwirq, enable);
+		if (handler->present &&
+		    cpumask_test_cpu(cpu, &handler->priv->lmask))
+			plic_toggle(handler, d->hwirq, enable);
 	}
 }
 
 static void plic_irq_unmask(struct irq_data *d)
 {
-	unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
-					   cpu_online_mask);
+	struct cpumask amask;
+	unsigned int cpu;
+	struct plic_priv *priv = irq_get_chip_data(d->irq);
+
+	cpumask_and(&amask, &priv->lmask, cpu_online_mask);
+	cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
+					   &amask);
 	if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
 		return;
-	plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
+	plic_irq_toggle(cpumask_of(cpu), d, 1);
 }
 
 static void plic_irq_mask(struct irq_data *d)
 {
-	plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
+	struct plic_priv *priv = irq_get_chip_data(d->irq);
+
+	plic_irq_toggle(&priv->lmask, d, 0);
 }
 
 #ifdef CONFIG_SMP
@@ -120,17 +134,21 @@ static int plic_set_affinity(struct irq_data *d,
 			     const struct cpumask *mask_val, bool force)
 {
 	unsigned int cpu;
+	struct cpumask amask;
+	struct plic_priv *priv = irq_get_chip_data(d->irq);
+
+	cpumask_and(&amask, &priv->lmask, mask_val);
 
 	if (force)
-		cpu = cpumask_first(mask_val);
+		cpu = cpumask_first(&amask);
 	else
-		cpu = cpumask_any_and(mask_val, cpu_online_mask);
+		cpu = cpumask_any_and(&amask, cpu_online_mask);
 
 	if (cpu >= nr_cpu_ids)
 		return -EINVAL;
 
-	plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
-	plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
+	plic_irq_toggle(&priv->lmask, d, 0);
+	plic_irq_toggle(cpumask_of(cpu), d, 1);
 
 	irq_data_update_effective_affinity(d, cpumask_of(cpu));
 
@@ -191,8 +209,6 @@ static const struct irq_domain_ops plic_irqdomain_ops = {
 	.free		= irq_domain_free_irqs_top,
 };
 
-static struct irq_domain *plic_irqdomain;
-
 /*
  * Handling an interrupt is a two-step process: first you claim the interrupt
  * by reading the claim register, then you complete the interrupt by writing
@@ -209,7 +225,7 @@ static void plic_handle_irq(struct pt_regs *regs)
 
 	csr_clear(CSR_IE, IE_EIE);
 	while ((hwirq = readl(claim))) {
-		int irq = irq_find_mapping(plic_irqdomain, hwirq);
+		int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);
 
 		if (unlikely(irq <= 0))
 			pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
@@ -265,15 +281,17 @@ static int __init plic_init(struct device_node *node,
 {
 	int error = 0, nr_contexts, nr_handlers = 0, i;
 	u32 nr_irqs;
+	struct plic_priv *priv;
 
-	if (plic_regs) {
-		pr_warn("PLIC already present.\n");
-		return -ENXIO;
-	}
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
 
-	plic_regs = of_iomap(node, 0);
-	if (WARN_ON(!plic_regs))
-		return -EIO;
+	priv->regs = of_iomap(node, 0);
+	if (WARN_ON(!priv->regs)) {
+		error = -EIO;
+		goto out_free_priv;
+	}
 
 	error = -EINVAL;
 	of_property_read_u32(node, "riscv,ndev", &nr_irqs);
@@ -287,9 +305,9 @@ static int __init plic_init(struct device_node *node,
 		goto out_iounmap;
 
 	error = -ENOMEM;
-	plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
-			&plic_irqdomain_ops, NULL);
-	if (WARN_ON(!plic_irqdomain))
+	priv->irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
+			&plic_irqdomain_ops, priv);
+	if (WARN_ON(!priv->irqdomain))
 		goto out_iounmap;
 
 	for (i = 0; i < nr_contexts; i++) {
@@ -334,13 +352,14 @@ static int __init plic_init(struct device_node *node,
 			goto done;
 		}
 
+		cpumask_set_cpu(cpu, &priv->lmask);
 		handler->present = true;
 		handler->hart_base =
-			plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
+			priv->regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
 		raw_spin_lock_init(&handler->enable_lock);
 		handler->enable_base =
-			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
-
+			priv->regs + ENABLE_BASE + i * ENABLE_PER_HART;
+		handler->priv = priv;
 done:
 		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
 			plic_toggle(handler, hwirq, 0);
@@ -356,7 +375,9 @@ static int __init plic_init(struct device_node *node,
 	return 0;
 
 out_iounmap:
-	iounmap(plic_regs);
+	iounmap(priv->regs);
+out_free_priv:
+	kfree(priv);
 	return error;
 }
 
-- 
2.25.0