echo bone_eqep1 > $SLOTS
-bash: echo: write error: File exists
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$ cat /sys/devices/platform/bone_capemgr/slots
0: PF---- -1
1: PF---- -1
2: PF---- -1
3: PF---- -1
6: P-O-L- 0 Override Board Name,00A0,Override Manuf,bone_eqep2
7: P-O-L- 1 Override Board Name,00A0,Override Manuf,bone_eqep1
$ config-pin -l P8_31
default gpio gpio_pu gpio_pd uart
This error looks bad:
[ 456.118649] bone_capemgr bone_capemgr: part_number 'bone_eqep1', version 'N/A'
[ 456.118721] bone_capemgr bone_capemgr: slot #7: override
[ 456.118762] bone_capemgr bone_capemgr: Using override eeprom data at slot 7
[ 456.118809] bone_capemgr bone_capemgr: slot #7: 'Override Board Name,00A0,Override Manuf,bone_eqep1'
[ 456.134771] platform 48302180.eqep: Cannot lookup hwmod 'eqep1'
[ 456.156907] eqep 48302180.eqep: ver. 1.0
[ 456.157294] eqep 48302180.eqep: failed to get clock
[ 456.177397] eqep: probe of 48302180.eqep failed with error -2
[ 456.177984] bone_capemgr bone_capemgr: slot #7: dtbo 'bone_eqep1-00A0.dtbo' loaded; overlay id #1
$ lsmod |grep eqep
tieqep 8758 0
Looks like the driver is failing here
// Get a handle to the system clock object
clk = devm_clk_get(&pdev->dev, "fck");
if (IS_ERR(clk)) {
dev_err(&pdev->dev, "failed to get clock\n");
return PTR_ERR(clk);
}
This patch looks interesting. Maybe the same issue?
https://patchwork.kernel.org/patch/9005611/
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Thanks for following up.I've been using the tieqep module to read absolute position count of a rotary encoder knob. I'm curious what other use cases people have for eQEP?
The reason I ask is I think a new driver needs to be written and it would be good to know which features of the eQEP peripheral should be implemented.
The existing tieqep driver is out of tree and seems unlikely to be included in the mainline Linux kernel. We are able to use it on BeagleBone because Robert includes it as a patch in his kernel builds.The IIO subsystem now has infrastructure for encoders. I am thinking that an IIO driver should be written for eQEP with the goal of being merged into the mainline kernel.Thoughts?
eCAP is interesting as there seems to be two modes: capture input, and PWM output. The use of eCAP as PWM output is already supported in mainline as part of epwmss.However, the eCAP input driver written Matt Porter is still out-of-tree and carried as a patch by Robert. At least this my understanding after chatting with Robert Nelson and Michael Welling last week.eCAP input seems to be another candidate to upstream. Question is which subsystem fits best.