Message-ID: <CAOuPNLhx1RcrTeVr7CPfAT6grmiZW1RBZbDioFP+jN5N91O6sw@mail.gmail.com>
Date:   Tue, 22 May 2018 00:21:30 +0530
From:   Pintu Kumar <pintu.ping@...il.com>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        open list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        kernelnewbies@...nelnewbies.org
Subject: Re: Delivery Status Notification (Failure)

Dear Lucas,

Can you give me some pointers on how to set affinity for entire GPIO Bank.
Currently I am exploring drivers/gpio/gpio-mxc.c to find out how the
GPIO banks are set up.

I also found that affinity can be set using: desc->irq_data.affinity,
may be by using cpumask_copy(...).
But still I am not familiar with this.

So, I need your help.


Thank You!

Regards,
Pintu



On Thu, May 17, 2018 at 6:58 PM, Pintu Kumar <pintu.ping@...il.com> wrote:
> On Mon, May 14, 2018 at 7:58 PM, Pintu Kumar <pintu.ping@...il.com> wrote:
>>
>> On Mon, May 14, 2018 at 6:41 PM, Lucas Stach <l.stach@...gutronix.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@...il.com>
>> >> wrote:
>> >> > On Fri, May 11, 2018 at 6:34 PM, Lucas Stach <l.stach@...gutronix.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

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