How to read back a fan speed?
I am on a custom board using an i.MX6. I am using Yocto (Pyro) to build my kernel (4.14.16).
I am using the generic imx6qdl.dtsi device tree entry for PWM2 to drive the fan and it appears to work fine. The fan has a Tachometer input, which is connected to GPIO2_7. How do I read the fan speed? I have seen device tree blobs for cooling devices, but none of the examples seem to have a tachometer to monitor the fan's speed.
embedded yocto device-tree fan
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
add a comment |
I am on a custom board using an i.MX6. I am using Yocto (Pyro) to build my kernel (4.14.16).
I am using the generic imx6qdl.dtsi device tree entry for PWM2 to drive the fan and it appears to work fine. The fan has a Tachometer input, which is connected to GPIO2_7. How do I read the fan speed? I have seen device tree blobs for cooling devices, but none of the examples seem to have a tachometer to monitor the fan's speed.
embedded yocto device-tree fan
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
Have you checked/sys/class/hwmon/(and/sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.
– derobert
Mar 8 at 20:53
I did. I could set the PWM for the fan from the/sys/class/pwm/but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in/sys/class/hwmonwere temperature sensors.
– Eskimoalva
Mar 11 at 12:23
add a comment |
I am on a custom board using an i.MX6. I am using Yocto (Pyro) to build my kernel (4.14.16).
I am using the generic imx6qdl.dtsi device tree entry for PWM2 to drive the fan and it appears to work fine. The fan has a Tachometer input, which is connected to GPIO2_7. How do I read the fan speed? I have seen device tree blobs for cooling devices, but none of the examples seem to have a tachometer to monitor the fan's speed.
embedded yocto device-tree fan
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
I am on a custom board using an i.MX6. I am using Yocto (Pyro) to build my kernel (4.14.16).
I am using the generic imx6qdl.dtsi device tree entry for PWM2 to drive the fan and it appears to work fine. The fan has a Tachometer input, which is connected to GPIO2_7. How do I read the fan speed? I have seen device tree blobs for cooling devices, but none of the examples seem to have a tachometer to monitor the fan's speed.
embedded yocto device-tree fan
embedded yocto device-tree fan
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
asked Mar 6 at 16:33
EskimoalvaEskimoalva
334
334
Have you checked/sys/class/hwmon/(and/sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.
– derobert
Mar 8 at 20:53
I did. I could set the PWM for the fan from the/sys/class/pwm/but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in/sys/class/hwmonwere temperature sensors.
– Eskimoalva
Mar 11 at 12:23
add a comment |
Have you checked/sys/class/hwmon/(and/sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.
– derobert
Mar 8 at 20:53
I did. I could set the PWM for the fan from the/sys/class/pwm/but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in/sys/class/hwmonwere temperature sensors.
– Eskimoalva
Mar 11 at 12:23
Have you checked
/sys/class/hwmon/ (and /sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.– derobert
Mar 8 at 20:53
Have you checked
/sys/class/hwmon/ (and /sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.– derobert
Mar 8 at 20:53
I did. I could set the PWM for the fan from the
/sys/class/pwm/ but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in /sys/class/hwmon were temperature sensors.– Eskimoalva
Mar 11 at 12:23
I did. I could set the PWM for the fan from the
/sys/class/pwm/ but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in /sys/class/hwmon were temperature sensors.– Eskimoalva
Mar 11 at 12:23
add a comment |
1 Answer
1
active
oldest
votes
I was unable to find a device tree solution, but found enough code snippets to make an application to read it. Basically I just set up an interrupt on the GPIO and used clock_gettime to measure the period between edges. It requires a lot of filtering, but I am only using it to make sure the fan is running so that is fine.
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
add a comment |
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1 Answer
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I was unable to find a device tree solution, but found enough code snippets to make an application to read it. Basically I just set up an interrupt on the GPIO and used clock_gettime to measure the period between edges. It requires a lot of filtering, but I am only using it to make sure the fan is running so that is fine.
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
add a comment |
I was unable to find a device tree solution, but found enough code snippets to make an application to read it. Basically I just set up an interrupt on the GPIO and used clock_gettime to measure the period between edges. It requires a lot of filtering, but I am only using it to make sure the fan is running so that is fine.
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
add a comment |
I was unable to find a device tree solution, but found enough code snippets to make an application to read it. Basically I just set up an interrupt on the GPIO and used clock_gettime to measure the period between edges. It requires a lot of filtering, but I am only using it to make sure the fan is running so that is fine.
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
I was unable to find a device tree solution, but found enough code snippets to make an application to read it. Basically I just set up an interrupt on the GPIO and used clock_gettime to measure the period between edges. It requires a lot of filtering, but I am only using it to make sure the fan is running so that is fine.
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
answered Mar 8 at 20:09
EskimoalvaEskimoalva
334
334
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
add a comment |
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
BTW, might be easier to count interrupts instead, and e.g., read your counter once per second (having your read thread sleep). Then you probably won't need filtering.
– derobert
Mar 11 at 15:49
add a comment |
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Have you checked
/sys/class/hwmon/(and/sys/class/pwm/)? I'm guessing yes, but just want to be sure there isn't an easy solution there.– derobert
Mar 8 at 20:53
I did. I could set the PWM for the fan from the
/sys/class/pwm/but there was no mechanism to read back the speed (just the PWM that i had set it to). All that I have in/sys/class/hwmonwere temperature sensors.– Eskimoalva
Mar 11 at 12:23