From: Samuel Holland <samuel@sholland.org> To: Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <maz@kernel.org>, Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: Samuel Holland <samuel@sholland.org>, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: [PATCH v3 2/2] irqchip/sifive-plic: Separate the enable and mask operations Date: Fri, 1 Jul 2022 15:24:40 -0500 [thread overview] Message-ID: <20220701202440.59059-3-samuel@sholland.org> (raw) In-Reply-To: <20220701202440.59059-1-samuel@sholland.org> The PLIC has two per-IRQ checks before sending an IRQ to a hart context. First, it checks that the IRQ's priority is nonzero. Then, it checks that the enable bit is set for that combination of IRQ and context. Currently, the PLIC driver sets both the priority value and the enable bit in its (un)mask operations. However, modifying the enable bit is problematic for two reasons: 1) The enable bits are packed, so changes are not atomic and require taking a spinlock. 2) The following requirement from the PLIC spec, which explains the racy (un)mask operations in plic_irq_eoi(): If the completion ID does not match an interrupt source that is currently enabled for the target, the completion is silently ignored. Both of these problems are solved by using the priority value to mask IRQs. Each IRQ has a separate priority register, so writing the priority value is atomic. And since the enable bit remains set while an IRQ is masked, the EOI operation works normally. The enable bits are still used to control the IRQ's affinity. Signed-off-by: Samuel Holland <samuel@sholland.org> --- Changes in v3: - Rebased on top of irqchip-next drivers/irqchip/irq-sifive-plic.c | 55 +++++++++++++++++++------------ 1 file changed, 34 insertions(+), 21 deletions(-) diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c index 46595e607b0e..ba4938188570 100644 --- a/drivers/irqchip/irq-sifive-plic.c +++ b/drivers/irqchip/irq-sifive-plic.c @@ -108,9 +108,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, struct irq_data *d, int enable) { int cpu; - struct plic_priv *priv = irq_data_get_irq_chip_data(d); - 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); @@ -118,16 +116,37 @@ static inline void plic_irq_toggle(const struct cpumask *mask, } } -static void plic_irq_unmask(struct irq_data *d) +static void plic_irq_enable(struct irq_data *d) { plic_irq_toggle(irq_data_get_effective_affinity_mask(d), d, 1); } -static void plic_irq_mask(struct irq_data *d) +static void plic_irq_disable(struct irq_data *d) { plic_irq_toggle(irq_data_get_effective_affinity_mask(d), d, 0); } +static void plic_irq_unmask(struct irq_data *d) +{ + struct plic_priv *priv = irq_data_get_irq_chip_data(d); + + writel(1, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID); +} + +static void plic_irq_mask(struct irq_data *d) +{ + struct plic_priv *priv = irq_data_get_irq_chip_data(d); + + writel(0, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID); +} + +static void plic_irq_eoi(struct irq_data *d) +{ + struct plic_handler *handler = this_cpu_ptr(&plic_handlers); + + writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); +} + #ifdef CONFIG_SMP static int plic_set_affinity(struct irq_data *d, const struct cpumask *mask_val, bool force) @@ -146,32 +165,21 @@ static int plic_set_affinity(struct irq_data *d, if (cpu >= nr_cpu_ids) return -EINVAL; - plic_irq_mask(d); + plic_irq_disable(d); irq_data_update_effective_affinity(d, cpumask_of(cpu)); - if (!irqd_irq_masked(d)) - plic_irq_unmask(d); + if (!irqd_irq_disabled(d)) + plic_irq_enable(d); return IRQ_SET_MASK_OK_DONE; } #endif -static void plic_irq_eoi(struct irq_data *d) -{ - struct plic_handler *handler = this_cpu_ptr(&plic_handlers); - - if (irqd_irq_masked(d)) { - plic_irq_unmask(d); - writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); - plic_irq_mask(d); - } else { - writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); - } -} - static struct irq_chip plic_edge_chip = { .name = "SiFive PLIC", + .irq_enable = plic_irq_enable, + .irq_disable = plic_irq_disable, .irq_ack = plic_irq_eoi, .irq_mask = plic_irq_mask, .irq_unmask = plic_irq_unmask, @@ -184,6 +192,8 @@ static struct irq_chip plic_edge_chip = { static struct irq_chip plic_chip = { .name = "SiFive PLIC", + .irq_enable = plic_irq_enable, + .irq_disable = plic_irq_disable, .irq_mask = plic_irq_mask, .irq_unmask = plic_irq_unmask, .irq_eoi = plic_irq_eoi, @@ -429,8 +439,11 @@ static int __init __plic_init(struct device_node *node, i * CONTEXT_ENABLE_SIZE; handler->priv = priv; done: - for (hwirq = 1; hwirq <= nr_irqs; hwirq++) + for (hwirq = 1; hwirq <= nr_irqs; hwirq++) { plic_toggle(handler, hwirq, 0); + writel(1, priv->regs + PRIORITY_BASE + + hwirq * PRIORITY_PER_ID); + } nr_handlers++; } -- 2.35.1
WARNING: multiple messages have this Message-ID (diff)
From: Samuel Holland <samuel@sholland.org> To: Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <maz@kernel.org>, Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: Samuel Holland <samuel@sholland.org>, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: [PATCH v3 2/2] irqchip/sifive-plic: Separate the enable and mask operations Date: Fri, 1 Jul 2022 15:24:40 -0500 [thread overview] Message-ID: <20220701202440.59059-3-samuel@sholland.org> (raw) In-Reply-To: <20220701202440.59059-1-samuel@sholland.org> The PLIC has two per-IRQ checks before sending an IRQ to a hart context. First, it checks that the IRQ's priority is nonzero. Then, it checks that the enable bit is set for that combination of IRQ and context. Currently, the PLIC driver sets both the priority value and the enable bit in its (un)mask operations. However, modifying the enable bit is problematic for two reasons: 1) The enable bits are packed, so changes are not atomic and require taking a spinlock. 2) The following requirement from the PLIC spec, which explains the racy (un)mask operations in plic_irq_eoi(): If the completion ID does not match an interrupt source that is currently enabled for the target, the completion is silently ignored. Both of these problems are solved by using the priority value to mask IRQs. Each IRQ has a separate priority register, so writing the priority value is atomic. And since the enable bit remains set while an IRQ is masked, the EOI operation works normally. The enable bits are still used to control the IRQ's affinity. Signed-off-by: Samuel Holland <samuel@sholland.org> --- Changes in v3: - Rebased on top of irqchip-next drivers/irqchip/irq-sifive-plic.c | 55 +++++++++++++++++++------------ 1 file changed, 34 insertions(+), 21 deletions(-) diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c index 46595e607b0e..ba4938188570 100644 --- a/drivers/irqchip/irq-sifive-plic.c +++ b/drivers/irqchip/irq-sifive-plic.c @@ -108,9 +108,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, struct irq_data *d, int enable) { int cpu; - struct plic_priv *priv = irq_data_get_irq_chip_data(d); - 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); @@ -118,16 +116,37 @@ static inline void plic_irq_toggle(const struct cpumask *mask, } } -static void plic_irq_unmask(struct irq_data *d) +static void plic_irq_enable(struct irq_data *d) { plic_irq_toggle(irq_data_get_effective_affinity_mask(d), d, 1); } -static void plic_irq_mask(struct irq_data *d) +static void plic_irq_disable(struct irq_data *d) { plic_irq_toggle(irq_data_get_effective_affinity_mask(d), d, 0); } +static void plic_irq_unmask(struct irq_data *d) +{ + struct plic_priv *priv = irq_data_get_irq_chip_data(d); + + writel(1, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID); +} + +static void plic_irq_mask(struct irq_data *d) +{ + struct plic_priv *priv = irq_data_get_irq_chip_data(d); + + writel(0, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID); +} + +static void plic_irq_eoi(struct irq_data *d) +{ + struct plic_handler *handler = this_cpu_ptr(&plic_handlers); + + writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); +} + #ifdef CONFIG_SMP static int plic_set_affinity(struct irq_data *d, const struct cpumask *mask_val, bool force) @@ -146,32 +165,21 @@ static int plic_set_affinity(struct irq_data *d, if (cpu >= nr_cpu_ids) return -EINVAL; - plic_irq_mask(d); + plic_irq_disable(d); irq_data_update_effective_affinity(d, cpumask_of(cpu)); - if (!irqd_irq_masked(d)) - plic_irq_unmask(d); + if (!irqd_irq_disabled(d)) + plic_irq_enable(d); return IRQ_SET_MASK_OK_DONE; } #endif -static void plic_irq_eoi(struct irq_data *d) -{ - struct plic_handler *handler = this_cpu_ptr(&plic_handlers); - - if (irqd_irq_masked(d)) { - plic_irq_unmask(d); - writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); - plic_irq_mask(d); - } else { - writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM); - } -} - static struct irq_chip plic_edge_chip = { .name = "SiFive PLIC", + .irq_enable = plic_irq_enable, + .irq_disable = plic_irq_disable, .irq_ack = plic_irq_eoi, .irq_mask = plic_irq_mask, .irq_unmask = plic_irq_unmask, @@ -184,6 +192,8 @@ static struct irq_chip plic_edge_chip = { static struct irq_chip plic_chip = { .name = "SiFive PLIC", + .irq_enable = plic_irq_enable, + .irq_disable = plic_irq_disable, .irq_mask = plic_irq_mask, .irq_unmask = plic_irq_unmask, .irq_eoi = plic_irq_eoi, @@ -429,8 +439,11 @@ static int __init __plic_init(struct device_node *node, i * CONTEXT_ENABLE_SIZE; handler->priv = priv; done: - for (hwirq = 1; hwirq <= nr_irqs; hwirq++) + for (hwirq = 1; hwirq <= nr_irqs; hwirq++) { plic_toggle(handler, hwirq, 0); + writel(1, priv->regs + PRIORITY_BASE + + hwirq * PRIORITY_PER_ID); + } nr_handlers++; } -- 2.35.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2022-07-01 20:24 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-01 20:24 [PATCH v3 0/2] irqchip: RISC-V PLIC cleanup and optimization Samuel Holland 2022-07-01 20:24 ` Samuel Holland 2022-07-01 20:24 ` [PATCH v3 1/2] irqchip/sifive-plic: Make better use of the effective affinity mask Samuel Holland 2022-07-01 20:24 ` Samuel Holland 2022-07-07 13:31 ` [irqchip: irq/irqchip-next] " irqchip-bot for Samuel Holland 2022-07-10 8:55 ` irqchip-bot for Samuel Holland 2022-07-01 20:24 ` Samuel Holland [this message] 2022-07-01 20:24 ` [PATCH v3 2/2] irqchip/sifive-plic: Separate the enable and mask operations Samuel Holland 2022-07-07 13:31 ` [irqchip: irq/irqchip-next] " irqchip-bot for Samuel Holland 2022-07-10 8:55 ` irqchip-bot for Samuel Holland
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