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Message-ID: <55D20B6E.2050209@linaro.org>
Date: Mon, 17 Aug 2015 18:27:26 +0200
From: Eric Auger <eric.auger@...aro.org>
To: Marc Zyngier <marc.zyngier@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Jason Cooper <jason@...edaemon.net>
CC: Christoffer Dall <christoffer.dall@...aro.org>,
Jiang Liu <jiang.liu@...ux.intel.com>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] irqchip: GIC: Convert to EOImode == 1
On 08/13/2015 10:28 AM, Marc Zyngier wrote:
> So far, GICv2 has been used in with EOImode == 0. The effect of this
in with?
> mode is to perform the priority drop and the deactivation of the
> interrupt at the same time.
>
> While this works perfectly for Linux (we only have a single priority),
> it causes issues when an interrupt is forwarded to a guest, and when
> we want the guest to perform the EOI itself.
>
> For this case, the GIC architecture provides EOImode == 1, where:
> - A write to the EOI register drops the priority of the interrupt and leaves
> it active. Other interrupts at the same priority level can now be taken,
> but the active interrupt cannot be taken again
> - A write to the DIR marks the interrupt as inactive, meaning it can
> now be taken again.
>
> We only enable this feature when booted in HYP mode and that
> the device-tree reporte a suitable CPU interface. Observable behaviour
reporte
> should remain unchanged.
I Get some checkpatch warnings.
I have no other remark on the code.
Eric
>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
> drivers/irqchip/irq-gic.c | 51 +++++++++++++++++++++++++++++++++++++++--
> include/linux/irqchip/arm-gic.h | 4 ++++
> 2 files changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index 4dd8826..b020c3a 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -46,6 +46,7 @@
> #include <asm/irq.h>
> #include <asm/exception.h>
> #include <asm/smp_plat.h>
> +#include <asm/virt.h>
>
> #include "irq-gic-common.h"
> #include "irqchip.h"
> @@ -82,6 +83,8 @@ static DEFINE_RAW_SPINLOCK(irq_controller_lock);
> #define NR_GIC_CPU_IF 8
> static u8 gic_cpu_map[NR_GIC_CPU_IF] __read_mostly;
>
> +static struct static_key supports_deactivate = STATIC_KEY_INIT_TRUE;
> +
> #ifndef MAX_GIC_NR
> #define MAX_GIC_NR 1
> #endif
> @@ -137,6 +140,14 @@ static inline unsigned int gic_irq(struct irq_data *d)
> return d->hwirq;
> }
>
> +static inline bool primary_gic_irq(struct irq_data *d)
> +{
> + if (MAX_GIC_NR > 1)
> + return irq_data_get_irq_chip_data(d) == &gic_data[0];
> +
> + return true;
> +}
> +
> /*
> * Routines to acknowledge, disable and enable interrupts
> */
> @@ -164,7 +175,14 @@ static void gic_unmask_irq(struct irq_data *d)
>
> static void gic_eoi_irq(struct irq_data *d)
> {
> - writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
> + u32 deact_offset = GIC_CPU_EOI;
> +
> + if (static_key_true(&supports_deactivate)) {
> + if (primary_gic_irq(d))
> + deact_offset = GIC_CPU_DEACTIVATE;
> + }
> +
> + writel_relaxed(gic_irq(d), gic_cpu_base(d) + deact_offset);
> }
>
> static int gic_irq_set_irqchip_state(struct irq_data *d,
> @@ -272,11 +290,15 @@ static void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
> irqnr = irqstat & GICC_IAR_INT_ID_MASK;
>
> if (likely(irqnr > 15 && irqnr < 1021)) {
> + if (static_key_true(&supports_deactivate))
> + writel_relaxed(irqstat, cpu_base + GIC_CPU_EOI);
> handle_domain_irq(gic->domain, irqnr, regs);
> continue;
> }
> if (irqnr < 16) {
> writel_relaxed(irqstat, cpu_base + GIC_CPU_EOI);
> + if (static_key_true(&supports_deactivate))
> + writel_relaxed(irqstat, cpu_base + GIC_CPU_DEACTIVATE);
> #ifdef CONFIG_SMP
> handle_IPI(irqnr, regs);
> #endif
> @@ -359,6 +381,10 @@ static void gic_cpu_if_up(void)
> {
> void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
> u32 bypass = 0;
> + u32 mode = 0;
> +
> + if (static_key_true(&supports_deactivate))
> + mode = GIC_CPU_CTRL_EOImodeNS;
>
> /*
> * Preserve bypass disable bits to be written back later
> @@ -366,7 +392,7 @@ static void gic_cpu_if_up(void)
> bypass = readl(cpu_base + GIC_CPU_CTRL);
> bypass &= GICC_DIS_BYPASS_MASK;
>
> - writel_relaxed(bypass | GICC_ENABLE, cpu_base + GIC_CPU_CTRL);
> + writel_relaxed(bypass | mode | GICC_ENABLE, cpu_base + GIC_CPU_CTRL);
> }
>
>
> @@ -986,6 +1012,8 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
> register_cpu_notifier(&gic_cpu_notifier);
> #endif
> set_handle_irq(gic_handle_irq);
> + if (static_key_true(&supports_deactivate))
> + pr_info ("GIC: Using split EOI/Deactivate mode\n");
> }
>
> gic_dist_init(gic);
> @@ -1001,6 +1029,7 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> {
> void __iomem *cpu_base;
> void __iomem *dist_base;
> + struct resource cpu_res;
> u32 percpu_offset;
> int irq;
>
> @@ -1013,6 +1042,16 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> cpu_base = of_iomap(node, 1);
> WARN(!cpu_base, "unable to map gic cpu registers\n");
>
> + of_address_to_resource(node, 1, &cpu_res);
> +
> + /*
> + * Disable split EOI/Deactivate if either HYP is not available
> + * or the CPU interface is too small.
> + */
> + if (gic_cnt == 0 && (!is_hyp_mode_available() ||
> + resource_size(&cpu_res) < SZ_8K))
> + static_key_slow_dec(&supports_deactivate);
> +
> if (of_property_read_u32(node, "cpu-offset", &percpu_offset))
> percpu_offset = 0;
>
> @@ -1132,6 +1171,14 @@ gic_v2_acpi_init(struct acpi_table_header *table)
> }
>
> /*
> + * Disable split EOI/Deactivate if HYP is not available. ACPI
> + * guarantees that we'll always have a GICv2, so the CPU
> + * interface will always be the right size.
> + */
> + if (!is_hyp_mode_available())
> + static_key_slow_dec(&supports_deactivate);
> +
> + /*
> * Initialize zero GIC instance (no multi-GIC support). Also, set GIC
> * as default IRQ domain to allow for GSI registration and GSI to IRQ
> * number translation (see acpi_register_gsi() and acpi_gsi_to_irq()).
> diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
> index 9de976b..b1533c0 100644
> --- a/include/linux/irqchip/arm-gic.h
> +++ b/include/linux/irqchip/arm-gic.h
> @@ -20,9 +20,13 @@
> #define GIC_CPU_ALIAS_BINPOINT 0x1c
> #define GIC_CPU_ACTIVEPRIO 0xd0
> #define GIC_CPU_IDENT 0xfc
> +#define GIC_CPU_DEACTIVATE 0x1000
>
> #define GICC_ENABLE 0x1
> #define GICC_INT_PRI_THRESHOLD 0xf0
> +
> +#define GIC_CPU_CTRL_EOImodeNS (1 << 9)
> +
> #define GICC_IAR_INT_ID_MASK 0x3ff
> #define GICC_INT_SPURIOUS 1023
> #define GICC_DIS_BYPASS_MASK 0x1e0
>
--
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