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

[Youlin Pei <youlin.pei@mediatek.com>]

On Fri, 2016-11-04 at 22:21 +0000, Marc Zyngier wrote:
> On Fri, Nov 04 2016 at 04:42:57 AM, Youlin Pei <youlin.pei@mediatek.com> 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 <youlin.pei@mediatek.com> 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 <youlin.pei@mediatek.com>
> >> > ---
> >> >  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 <youlin.pei@mediatek.com>
> >> > + *
> >> > + * 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 ve
> >
> >> 
> >> > +}
> >> > +
> >> > +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?

I had planned to ACK the status in cirq suspend callback, but
encountered a problem.
following is a piece of code from
http://lxr.free-electrons.com/source/kernel/power/suspend.c#L361

arch_suspend_disable_irqs(); ---step1
BUG_ON(!irqs_disabled());

error = syscore_suspend();
           |
           ---cirq suspend(); ---step2

if ack the status in cirq suspend, the interrupts will be lost which
happened during step1 to step2.

So would you mind give me some suggestions about this?
Thanks a lot!
> 
> Thanks,
> 
> 	M.