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From:   Pintu Kumar <pintu.ping@gmail.com>
Date:   Thu, 17 May 2018 18:58:26 +0530
Message-ID: <CAOuPNLiaAc16BoMQ=EiqWiyMs14MP4YPOTUf42XbUs2xNYzUUg@mail.gmail.com>
Subject: Re: Delivery Status Notification (Failure)
To:     Lucas Stach <l.stach@pengutronix.de>
Cc:     Russell King - ARM Linux <linux@armlinux.org.uk>,
        open list <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        kernelnewbies@kernelnewbies.org
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On Mon, May 14, 2018 at 7:58 PM, Pintu Kumar <pintu.ping@gmail.com> wrote:
>
> On Mon, May 14, 2018 at 6:41 PM, Lucas Stach <l.stach@pengutronix.de> wrote:
> > Am Montag, den 14.05.2018, 17:42 +0530 schrieb Pintu Kumar:
> >> Hi,
> >>
> >> Is there any work around possible to set IRQ affinity for some GPIO
> >> interrupt ?
> >> How to avoid CPU0 to receive the current GPIO interrupt ?
> >> How do we assign GPIO interrupts to any CPU other than CPU0 ?
> >> Is it possible to isolate CPU0 for a sometime, from my GPIO driver so
> >> that GPIO interrupt can be served by another CPU ?
> >>
> >> Need your inputs to decide whether it is still possible to set
> >> affinity for GPIO interrupt, or its impossible ?
> >
> > This is not possible. The GPIO IRQs are aggregated into one GPC/GIC IRQ
> > line per GPIO bank, so it is not possible to change affinity of a
> > single GPIO interrupt to another CPU.
>
> OK. Thanks for your confirmation.
>
> > Best we could do is change the
> > affinity of the whole bank,
>

Hi,

I found that the driver is responsible for setting GPIO bank in i.MX7:
https://elixir.bootlin.com/linux/v4.2/source/drivers/gpio/gpio-mxc.c

However I still dont know how to set the cpumask for one of the GPIO Bank.

From this link, it seems it is possible to set affinity for a GPIO IRQ.
https://community.nxp.com/thread/303144

But when I try it form my GPIO138 (GPIO5_IO10) it did not help.

So, as you said, I wanted to change affinity for the whole GPIO bank and try it.
Please give me some pointers.

Thanks


> OK. How can we do this on the fly from my driver code.
> If you have any reference please let me know.
> This is required only for experimental purpose to prove the point to be mgmt.
> My idea is, from the driver, change the affinity of the whole bank.
> So, the GPIO interrupt can be delivered on to this specific CPU bank.
> Once I am done, I will revert back to the old bank.
> Please give me some hint on how to do this from my kernel module....
>
>
> > but given the limited usefulness of
> > something like that, nobody bothered to implement such a thing.
> >
> > Regards,
> > Lucas
> >
> >>
> >>
> >> On Fri, May 11, 2018 at 8:07 PM, Pintu Kumar <pintu.ping@gmail.com>
> >> wrote:
> >> > On Fri, May 11, 2018 at 6:34 PM, Lucas Stach <l.stach@pengutronix.d
> >> > e> wrote:
> >> > > Am Freitag, den 11.05.2018, 13:39 +0100 schrieb Russell King -
> >> > > ARM Linux:
> >> > > > On Fri, May 11, 2018 at 05:07:37PM +0530, Pintu Kumar wrote:
> >> > > > > Hi,
> >> > > > >
> >> > > > > I need one help.
> >> > > > > I am using i.MX7 Sabre board with kernel version 4.1.15
> >> > > > >
> >> > > > > Let's say I am interested in GPIO number: 21
> >> > > > > I wanted to set CPU affinity for particular GPIO->IRQ number,
> >> > > > > so I
> >> > > > > tried the below steps:
> >> > > > > root@10:~# echo 21 > /sys/class/gpio/export
> >> > > > > root@10:~# echo "rising" > /sys/class/gpio/gpio21/edge
> >> > > > > root@10:~# cat /proc/interrupts | grep 21
> >> > > > >   47: 0 0 gpio-mxc 21 Edge gpiolib
> >> > > > > root@10:~# cat /sys/class/gpio/gpio21/direction
> >> > > > > in
> >> > > > > root@10:~# cat /proc/irq/47/smp_affinity
> >> > > > > 3
> >> > > > > root@10:~# echo 2 > /proc/irq/47/smp_affinity
> >> > > > > -bash: echo: write error: Input/output error
> >> > > > >
> >> > > > > But I get input/output error.
> >> > > > > When I debug further, found that irq_can_set_affinity is
> >> > > > > returning 0:
> >> > > > > [    0.000000] genirq: irq_can_set_affinity (0): balance: 1,
> >> > > > > irq_data.chip: a81b7e48, irq_set_affinity:   (null)
> >> > > > > [    0.000000] write_irq_affinity: FAIL
> >> > > > >
> >> > > > > I also tried first setting /proc/irq/default_smp_affinity to
> >> > > > > 2 (from 3).
> >> > > > > This change is working, but the smp_affinity setting for the
> >> > > > > new IRQ
> >> > > > > is not working.
> >> > > > >
> >> > > > > When I try to set smp_affinity for mmc0, then it works.
> >> > > > > # cat /proc/interrupts | grep mmc
> >> > > > > 295:         55          0     GPCV2  22 Edge      mmc0
> >> > > > > 296:          0          0     GPCV2  23 Edge      mmc1
> >> > > > > 297:         52          0     GPCV2  24 Edge      mmc2
> >> > > > >
> >> > > > > root@10:~# echo 2 > /proc/irq/295/smp_affinity
> >> > > > > root@10:~#
> >> > > > >
> >> > > > >
> >> > > > > So, I wanted to know what are the conditions for which
> >> > > > > setting
> >> > > > > smp_affinity for an IRQ will work ?
> >> > > > >
> >> > > > > Is there any way by which I can set CPU affinity to a GPIO ->
> >> > > > > IRQ ?
> >> > > > > Whether, irq_set_affinity_hint() will work in this case ?
> >> > > >
> >> > > > IRQ affinity is only supported where interrupts are _directly_
> >> > > > wired to
> >> > > > the GIC.  It's the GIC which does the interrupt steering to the
> >> > > > CPU
> >> > > > cores.
> >> > > >
> >> > > > Interrupts on downstream interrupt controllers (such as GPCV2)
> >> > > > have no
> >> > > > ability to be directed independently to other CPUs - the only
> >> > > > possible
> >> > > > way to change the mapping is to move _all_ interrupts on that
> >> > > > controller,
> >> > > > and any downstream chained interrupts at GIC level.
> >> > > >
> >> > > > Hence why Interrupt 295 has no irq_set_affinity function: there
> >> > > > is no way
> >> > > > for the interrupt controller itself to change the affinity of
> >> > > > the input
> >> > > > interrupt.
> >> > >
> >> > > The GPCv2 though is a secondary IRQ controller which has a 1:1
> >> > > mapping
> >> > > of its input IRQs to the upstream GIC IRQ lines. Affinity can
> >> > > thus be
> >> > > handled by forwarding the request to the GIC by
> >> > > irq_chip_set_affinity_parent().
> >> > >
> >> > > As this is handled correctly in the upstream kernel since the
> >> > > first
> >> > > commit introducing support for the GPCv2, it seems the issue is
> >> > > only
> >> > > present in some downstream kernel.
> >> > >
> >> >
> >> > OK. Thanks so much for your reply.
> >> >
> >> > I saw some of the drivers using irq_set_affinity_hint() to force
> >> > the
> >> > IRQ affinity to a particular CPU.
> >> > This is the sample:
> >> > {
> >> > cpumask_clear(mask);
> >> > cpumask_set_cpu(cpu, mask);
> >> > irq_set_affinity_hint(irq, mask);
> >> > }
> >> >
> >> > Whether this logic will work for a particular GPIO pin ?
> >> >


>
> >> >
> >> > > Regards,
> >> > > Lucas