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Date: Tue, 06 Jul 2021 14:21:08 +0100
From: Marc Zyngier <maz@...nel.org>
To: Huacai Chen <chenhuacai@...ngson.cn>
Cc: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
Xuefeng Li <lixuefeng@...ngson.cn>,
Huacai Chen <chenhuacai@...il.com>,
Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH 7/9] irqchip: Add LoongArch CPU interrupt controller support
On Tue, 06 Jul 2021 04:09:02 +0100,
Huacai Chen <chenhuacai@...ngson.cn> wrote:
>
> We are preparing to add new Loongson (based on LoongArch, not MIPS)
> support. This patch add LoongArch CPU interrupt controller support.
>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
> drivers/irqchip/Kconfig | 10 ++++
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-loongarch-cpu.c | 87 +++++++++++++++++++++++++++++
> 3 files changed, 98 insertions(+)
> create mode 100644 drivers/irqchip/irq-loongarch-cpu.c
>
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index 084bc4c2eebd..443c3a7a0cc1 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -528,6 +528,16 @@ config EXYNOS_IRQ_COMBINER
> Say yes here to add support for the IRQ combiner devices embedded
> in Samsung Exynos chips.
>
> +config IRQ_LOONGARCH_CPU
> + bool
> + select GENERIC_IRQ_CHIP
> + select IRQ_DOMAIN
> + select GENERIC_IRQ_EFFECTIVE_AFF_MASK
> + help
> + Support for the LoongArch CPU Interrupt Controller. For details of
> + irq chip hierarchy on LoongArch platforms please read the document
> + Documentation/loongarch/irq-chip-model.rst.
> +
> config LOONGSON_LIOINTC
> bool "Loongson Local I/O Interrupt Controller"
> depends on MACH_LOONGSON64
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index f88cbf36a9d2..4e34eebe180b 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -105,6 +105,7 @@ obj-$(CONFIG_LS1X_IRQ) += irq-ls1x.o
> obj-$(CONFIG_TI_SCI_INTR_IRQCHIP) += irq-ti-sci-intr.o
> obj-$(CONFIG_TI_SCI_INTA_IRQCHIP) += irq-ti-sci-inta.o
> obj-$(CONFIG_TI_PRUSS_INTC) += irq-pruss-intc.o
> +obj-$(CONFIG_IRQ_LOONGARCH_CPU) += irq-loongarch-cpu.o
> obj-$(CONFIG_LOONGSON_LIOINTC) += irq-loongson-liointc.o
> obj-$(CONFIG_LOONGSON_HTPIC) += irq-loongson-htpic.o
> obj-$(CONFIG_LOONGSON_HTVEC) += irq-loongson-htvec.o
> diff --git a/drivers/irqchip/irq-loongarch-cpu.c b/drivers/irqchip/irq-loongarch-cpu.c
> new file mode 100644
> index 000000000000..918d61a5a980
> --- /dev/null
> +++ b/drivers/irqchip/irq-loongarch-cpu.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020 Loongson Technologies, Inc.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqdomain.h>
> +
> +#include <asm/setup.h>
> +#include <asm/loongarchregs.h>
> +
> +static struct irq_domain *irq_domain;
> +
> +static inline void unmask_loongarch_irq(struct irq_data *d)
> +{
> + set_csr_ecfg(ECFGF(d->hwirq));
> +}
> +
> +static inline void mask_loongarch_irq(struct irq_data *d)
> +{
> + clear_csr_ecfg(ECFGF(d->hwirq));
> +}
> +
> +#define enable_loongarch_irq unmask_loongarch_irq
> +#define disable_loongarch_irq mask_loongarch_irq
> +
> +static struct irq_chip loongarch_cpu_irq_controller = {
> + .name = "LoongArch",
> + .irq_ack = mask_loongarch_irq,
> + .irq_mask = mask_loongarch_irq,
> + .irq_mask_ack = mask_loongarch_irq,
> + .irq_unmask = unmask_loongarch_irq,
> + .irq_eoi = unmask_loongarch_irq,
> + .irq_enable = enable_loongarch_irq,
> + .irq_disable = disable_loongarch_irq,
NAK. Clearly, you don't understand what these callbacks do.
> +};
> +
> +asmlinkage void __weak plat_irq_dispatch(int irq)
> +{
> + do_IRQ(irq_linear_revmap(irq_domain, irq));
> +}
NAK. If you are going to add a new architecture to Linux, do not mimic
the MIPS brain-damage. Have your new architecture to support multiple
interrupt controllers from day one without the need to add these silly
weak symbols.
Move the low-level code such as this into the architecture code, and
use the existing domain abstractions.
> +
> +static int loongarch_cpu_intc_map(struct irq_domain *d, unsigned int irq,
> + irq_hw_number_t hwirq)
> +{
> + struct irq_chip *chip;
> +
> + chip = &loongarch_cpu_irq_controller;
> + set_vi_handler(EXCCODE_INT_START + hwirq, plat_irq_dispatch);
> + irq_set_chip_and_handler(irq, chip, handle_percpu_irq);
> +
> + return 0;
> +}
> +
> +static const struct irq_domain_ops loongarch_cpu_intc_irq_domain_ops = {
> + .map = loongarch_cpu_intc_map,
> + .xlate = irq_domain_xlate_onecell,
Are all interrupts with the same trigger?
> +};
> +
> +
> +int __init loongarch_cpu_irq_init(struct device_node *of_node, struct device_node *parent)
> +{
> + int i;
> +
> + /* Mask interrupts. */
> + clear_csr_ecfg(ECFG0_IM);
> + clear_csr_estat(ESTATF_IP);
> +
> + irq_alloc_descs(-1, LOONGSON_CPU_IRQ_BASE, EXCCODE_INT_NUM, 0);
> +
> + for (i = LOONGSON_CPU_IRQ_BASE; i <= LOONGSON_CPU_LAST_IRQ; i++)
> + irq_set_noprobe(i);
> +
> + irq_domain = irq_domain_add_legacy(of_node, EXCCODE_INT_NUM,
> + LOONGSON_CPU_IRQ_BASE, 0, &loongarch_cpu_intc_irq_domain_ops, NULL);
Oh, the irony of using irq_domain_add_legacy() for a brand new
architecture...
> +
> + if (!irq_domain)
> + panic("Failed to add irqdomain for loongarch CPU");
> +
> + return 0;
> +}
> +
> +IRQCHIP_DECLARE(cpu_intc, "loongson,cpu-interrupt-controller", loongarch_cpu_irq_init);
As it stands, this driver has zero chance of being merged. You
seriously need to move your low-level interrupt handling code into the
21st century.
M.
--
Without deviation from the norm, progress is not possible.
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