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 ? Thanks, Pintu 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.de> 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