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 ? Thanks, Pintu