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 <20210706030904.1411775-8-chenhuacai@loongson.cn> <8735sr8tob.wl-maz@kernel.org>
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From:   Huacai Chen <chenhuacai@gmail.com>
Date:   Wed, 7 Jul 2021 12:57:17 +0800
Message-ID: <CAAhV-H4ToQ=r8f7pkf3JGoDj2MkrZA+MkMoDEVnQHYZA8exWiA@mail.gmail.com>
Subject: Re: [PATCH 7/9] irqchip: Add LoongArch CPU interrupt controller support
To:     Marc Zyngier <maz@kernel.org>
Cc:     Huacai Chen <chenhuacai@loongson.cn>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
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Hi, Marc,

On Tue, Jul 6, 2021 at 9:21 PM Marc Zyngier <maz@kernel.org> wrote:
>
> On Tue, 06 Jul 2021 04:09:02 +0100,
> Huacai Chen <chenhuacai@loongson.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@loongson.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.
Thanks, I will consider to rework the whole thing.

Huacai
>
> > +
> > +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.