I’m trying to generate clock signal on GPIO pin (ARM platform, mach-davinci, kernel 2.6.27) which will have something arroung 100kHz. Using tasklet with high priority to do that. Theory is simple, set gpio high, udelay for 5us, set gpio low, wait another 5us, but strange problems appear. First of all, can’t get this 5us of dalay, but it’s fine, looks like hw performance problem, so i moved to period = 40us (gives ~25kHz). Second problem is worst. Once per ~10ms udelay waits 3x longer than usual. I’m thinking that it’s hearbeat taking this time, but this is is unacceptable from protocol (which will be implemented on top of this) point of view. Is there any way to temporary disable heartbeat procedure, lets say, for 500ms ? Or maybe I’m doing it wrong from the beginning? Any comments?
I’m trying to generate clock signal on GPIO pin (ARM platform, mach-davinci, kernel 2.6.27)
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You cannot use tasklet for this kind of job. Tasklets can be preempted by interrupts. In some case your tasklet can be even executed in the process context!
If you absolutely have to do it this way, use an interrupt handler – get in, disable interrupts, do whatever you have to do and get out as fast as you can.