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SubjectRe: [PATCH v2 2/4] irqchip: Add Aspeed SCU interrupt controller


On Sat, 28 Sep 2019, at 06:28, Eddie James wrote:
> The Aspeed SOCs provide some interrupts through the System Control
> Unit registers. Add an interrupt controller that provides these
> interrupts to the system.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>
> ---
> Changes since v1:
> - add a spinlock to protect read-modify-write operation for irq masking
> - use readl/writel relaxed versions

What's your motivation? I might have missed some comments on v1. The
descriptions make me slightly nervous (not guaranteed to be ordered wrt
spinlocks).

> - add a comment explaining the irq status/enable register
> - provide affinity callback that returns -EINVAL
>
> MAINTAINERS | 1 +
> drivers/irqchip/Makefile | 2 +-
> drivers/irqchip/irq-aspeed-scu-ic.c | 233 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 235 insertions(+), 1 deletion(-)
> create mode 100644 drivers/irqchip/irq-aspeed-scu-ic.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c7e028c..b6db122 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2656,6 +2656,7 @@ M: Eddie James <eajames@linux.ibm.com>
> L: linux-aspeed@lists.ozlabs.org (moderated for non-subscribers)
> S: Maintained
>
> F: Documentation/devicetree/bindings/interrupt-controller/aspeed,ast2xxx-scu-ic.txt
> +F: drivers/irqchip/irq-aspeed-scu-ic.c
> F: include/dt-bindings/interrupt-controller/aspeed-scu-ic.h
>
> ASPEED VIDEO ENGINE DRIVER
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index cc7c439..fce6b1d 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -86,7 +86,7 @@ obj-$(CONFIG_MVEBU_PIC) += irq-mvebu-pic.o
> obj-$(CONFIG_MVEBU_SEI) += irq-mvebu-sei.o
> obj-$(CONFIG_LS_SCFG_MSI) += irq-ls-scfg-msi.o
> obj-$(CONFIG_EZNPS_GIC) += irq-eznps.o
> -obj-$(CONFIG_ARCH_ASPEED) += irq-aspeed-vic.o irq-aspeed-i2c-ic.o
> +obj-$(CONFIG_ARCH_ASPEED) += irq-aspeed-vic.o irq-aspeed-i2c-ic.o
> irq-aspeed-scu-ic.o
> obj-$(CONFIG_STM32_EXTI) += irq-stm32-exti.o
> obj-$(CONFIG_QCOM_IRQ_COMBINER) += qcom-irq-combiner.o
> obj-$(CONFIG_IRQ_UNIPHIER_AIDET) += irq-uniphier-aidet.o
> diff --git a/drivers/irqchip/irq-aspeed-scu-ic.c
> b/drivers/irqchip/irq-aspeed-scu-ic.c
> new file mode 100644
> index 0000000..64c3ac4
> --- /dev/null
> +++ b/drivers/irqchip/irq-aspeed-scu-ic.c
> @@ -0,0 +1,233 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Aspeed AST24XX, AST25XX, and AST26XX SCU Interrupt Controller
> + * Copyright 2019 IBM Corporation
> + *
> + * Eddie James <eajames@linux.ibm.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/irqdomain.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/io.h>
> +#include <linux/spinlock.h>
> +
> +#define ASPEED_SCU_IC_SHIFT 0
> +#define ASPEED_SCU_IC_ENABLE GENMASK(6, ASPEED_SCU_IC_SHIFT)
> +#define ASPEED_SCU_IC_NUM_IRQS 7
> +#define ASPEED_SCU_IC_STATUS_SHIFT 16
> +
> +#define ASPEED_AST2600_SCU_IC0_SHIFT 0
> +#define ASPEED_AST2600_SCU_IC0_ENABLE \
> + GENMASK(5, ASPEED_AST2600_SCU_IC0_SHIFT)
> +#define ASPEED_AST2600_SCU_IC0_NUM_IRQS 6
> +
> +#define ASPEED_AST2600_SCU_IC1_SHIFT 4
> +#define ASPEED_AST2600_SCU_IC1_ENABLE \
> + GENMASK(5, ASPEED_AST2600_SCU_IC1_SHIFT)
> +#define ASPEED_AST2600_SCU_IC1_NUM_IRQS 2
> +
> +struct aspeed_scu_ic {
> + unsigned long irq_enable;
> + unsigned long irq_shift;

> + unsigned int num_irqs;
> + void __iomem *reg;
> + struct irq_domain *irq_domain;
> + spinlock_t lock;
> +};
> +
> +static void aspeed_scu_ic_irq_handler(struct irq_desc *desc)
> +{
> + unsigned int irq;
> + unsigned long bit;
> + unsigned long enabled;
> + unsigned long max;
> + unsigned long status;
> + struct aspeed_scu_ic *scu_ic = irq_desc_get_handler_data(desc);
> + struct irq_chip *chip = irq_desc_get_chip(desc);
> +
> + chained_irq_enter(chip, desc);
> +
> + /*
> + * The SCU IC has just one register to control its operation and read
> + * status. The interrupt enable bits occupy the lower 16 bits of the
> + * register, while the interrupt status bits occupy the upper 16 bits.
> + * The status bit for a given interrupt is always 16 bits shifted from
> + * the enable bit for the same interrupt.
> + * Therefore, perform the IRQ operations in the enable bit space by
> + * shifting the status down to get the mapping and then back up to
> + * clear the bit.
> + */
> + status = readl_relaxed(scu_ic->reg);
> + enabled = status & scu_ic->irq_enable;
> + status = (status >> ASPEED_SCU_IC_STATUS_SHIFT) & enabled;
> +
> + bit = scu_ic->irq_shift;
> + max = scu_ic->num_irqs + bit;
> +
> + for_each_set_bit_from(bit, &status, max) {
> + irq = irq_find_mapping(scu_ic->irq_domain,
> + bit - scu_ic->irq_shift);
> + generic_handle_irq(irq);
> +
> + writel_relaxed(enabled | BIT(bit + ASPEED_SCU_IC_STATUS_SHIFT),
> + scu_ic->reg);
> + }
> +
> + chained_irq_exit(chip, desc);
> +}
> +
> +static void aspeed_scu_ic_irq_mask(struct irq_data *data)
> +{
> + struct aspeed_scu_ic *scu_ic = irq_data_get_irq_chip_data(data);
> + unsigned long bit = BIT(data->hwirq + scu_ic->irq_shift);
> + unsigned long flags;
> + unsigned long reg;
> +
> + spin_lock_irqsave(&scu_ic->lock, flags);

The SCU is represented by a syscon in the devicetree, which has a regmap,
which does it's own locking internally. You could use regmap_update_bits()
to do an atomic read/modify/write and this will provide consistency for
other SCU drivers that might be accessing shared registers. Nothing else
should _currently_ be touching the SCU IRQ status/enable register, but
using the regmap would give us a consistent approach across all SCU
drivers.

Andrew

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