Subject: [PATCH v2 2/3] irqchip: mtk-cirq: Add mediatek mtk-cirq implement

From: [email-masked] (Marc Zyngier)
Date: Fri, 04 Nov 2016 22:21:46 +0000

On Fri, Nov 04 2016 at 04:42:57 AM, Youlin Pei <[email-masked]> wrote:
> On Tue, 2016-11-01 at 20:49 +0000, Marc Zyngier wrote:
>> On Tue, Nov 01 2016 at 11:52:01 AM, Youlin Pei <[email-masked]> wrote:
>> > In Mediatek SOCs, the CIRQ is a low power interrupt controller
>> > designed to works outside MCUSYS which comprises with Cortex-Ax
>> > cores,CCI and GIC.
>> >
>> > The CIRQ controller is integrated in between MCUSYS( include
>> > Cortex-Ax, CCI and GIC ) and interrupt sources as the second
>> > level interrupt controller. The external interrupts which outside
>> > MCUSYS will feed through CIRQ then bypass to GIC. CIRQ can monitors
>> > all edge trigger interupts. When an edge interrupt is triggered,
>> > CIRQ can record the status and generate a pulse signal to GIC when
>> > flush command executed.
>> >
>> > When system enters sleep mode, MCUSYS will be turned off to improve
>> > power consumption, also GIC is power down. The edge trigger interrupts
>> > will be lost in this scenario without CIRQ.
>> >
>> > This commit provides the CIRQ irqchip implement.
>> >
>> > Signed-off-by: Youlin Pei <[email-masked]>
>> > ---
>> >  drivers/irqchip/Makefile       |    2 +-
>> >  drivers/irqchip/irq-mtk-cirq.c |  262 ++++++++++++++++++++++++++++++++++++++++
>> >  2 files changed, 263 insertions(+), 1 deletion(-)
>> >  create mode 100644 drivers/irqchip/irq-mtk-cirq.c
>> >
>> > diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
>> > index e4dbfc8..8f33580 100644
>> > --- a/drivers/irqchip/Makefile
>> > +++ b/drivers/irqchip/Makefile
>> > @@ -60,7 +60,7 @@ obj-$(CONFIG_BCM7120_L2_IRQ)		+= irq-bcm7120-l2.o
>> >  obj-$(CONFIG_BRCMSTB_L2_IRQ)		+= irq-brcmstb-l2.o
>> >  obj-$(CONFIG_KEYSTONE_IRQ)		+= irq-keystone.o
>> >  obj-$(CONFIG_MIPS_GIC)			+= irq-mips-gic.o
>> > -obj-$(CONFIG_ARCH_MEDIATEK)		+= irq-mtk-sysirq.o
>> > +obj-$(CONFIG_ARCH_MEDIATEK)		+= irq-mtk-sysirq.o irq-mtk-cirq.o
>> >  obj-$(CONFIG_ARCH_DIGICOLOR)		+= irq-digicolor.o
>> >  obj-$(CONFIG_RENESAS_H8300H_INTC)	+= irq-renesas-h8300h.o
>> >  obj-$(CONFIG_RENESAS_H8S_INTC)		+= irq-renesas-h8s.o
>> > diff --git a/drivers/irqchip/irq-mtk-cirq.c b/drivers/irqchip/irq-mtk-cirq.c
>> > new file mode 100644
>> > index 0000000..fc43ef3
>> > --- /dev/null
>> > +++ b/drivers/irqchip/irq-mtk-cirq.c
>> > @@ -0,0 +1,262 @@
>> > +/*
>> > + * Copyright (c) 2016 MediaTek Inc.
>> > + * Author: Youlin.Pei <[email-masked]>
>> > + *
>> > + * This program is free software; you can redistribute it and/or modify
>> > + * it under the terms of the GNU General Public License version 2 as
>> > + * published by the Free Software Foundation.
>> > + *
>> > + * This program is distributed in the hope that it will be useful,
>> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> > + * GNU General Public License for more details.
>> > + */
>> > +
>> > +#include <linux/irq.h>
>> > +#include <linux/irqchip.h>
>> > +#include <linux/irqdomain.h>
>> > +#include <linux/of.h>
>> > +#include <linux/of_irq.h>
>> > +#include <linux/of_address.h>
>> > +#include <linux/io.h>
>> > +#include <linux/slab.h>
>> > +#include <linux/syscore_ops.h>
>> > +
>> > +#define CIRQ_ACK	0x40
>> > +#define CIRQ_MASK_SET	0xc0
>> > +#define CIRQ_MASK_CLR	0x100
>> > +#define CIRQ_SENS_SET	0x180
>> > +#define CIRQ_SENS_CLR	0x1c0
>> > +#define CIRQ_POL_SET	0x240
>> > +#define CIRQ_POL_CLR	0x280
>> > +#define CIRQ_CONTROL	0x300
>> > +
>> > +#define CIRQ_EN	0x1
>> > +#define CIRQ_EDGE	0x2
>> > +#define CIRQ_FLUSH	0x4
>> > +
>> > +#define CIRQ_IRQ_NUM    0x200
>> > +
>> > +struct mtk_cirq_chip_data {
>> > +	void __iomem *base;
>> > +	unsigned int ext_irq_start;
>> > +};
>> > +
>> > +static struct mtk_cirq_chip_data *cirq_data;
>> 
>> Are you guaranteed that you'll only ever have a single CIRQ in any
>> system?
>
> In Mediatek's SOC, only hace a single CIRQ.
>
>> 
>> > +
>> > +static void mtk_cirq_write_mask(struct irq_data *data, unsigned int offset)
>> > +{
>> > +	struct mtk_cirq_chip_data *chip_data = data->chip_data;
>> > +	unsigned int cirq_num = data->hwirq;
>> > +	u32 mask = 1 << (cirq_num % 32);
>> > +
>> > +	writel(mask, chip_data->base + offset + (cirq_num / 32) * 4);
>> 
>> Why can't you use the relaxed accessors?
>
> It seems that i use wrong function, i will change the writel to
> writel_relaxed in next version.
>
>> 
>> > +}
>> > +
>> > +static void mtk_cirq_mask(struct irq_data *data)
>> > +{
>> > +	mtk_cirq_write_mask(data, CIRQ_MASK_SET);
>> > +	irq_chip_mask_parent(data);
>> > +}
>> > +
>> > +static void mtk_cirq_unmask(struct irq_data *data)
>> > +{
>> > +	mtk_cirq_write_mask(data, CIRQ_MASK_CLR);
>> > +	irq_chip_unmask_parent(data);
>> > +}
>> > +
>> > +static void mtk_cirq_eoi(struct irq_data *data)
>> > +{
>> > +	mtk_cirq_write_mask(data, CIRQ_ACK);
>> 
>> EOI and ACK have very different semantics. What is this write actually
>> doing? Also, you're now doing an additional MMIO write on each interrupt
>> EOI, doubling its cost. Do you really need to do actually signal the HW
>> that we've EOIed an interrupt? I would have hoped that you'd be able to
>> put it in "bypass" mode as long as you're not suspending...
>> 
>
> When external interrupt happened, CIRQ status register record the status
> even CIRQ is not enabled. when execute the flush command, CIRQ will
> resend the signals according to the status. So if don't clear the
> status, CIRQ will resend the wrong signals. the ACK write operation will
> clear the status.

But at this time, we haven't suspended yet, and there is nothing to
replay. Also, you only enable the edge capture when suspending. So what
are you ACKing here? Can't you simply clear everything right when
suspending and not do it at all on the fast path?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.