Hello List,
I have asked this before on several mailing lists, but still no solution,
so I am trying again here.
I'm having trouble with using FIQ interrupts with the ARM timer on raspberypi
zero, (BCM2835 chip).
I created a kernel module, and the test version of this driver can be found in
https://github.com/SietseAchterop/Batradio/blob/master/batradio_module/fiqtest_4.c
I made sure that FIQ is not used by USB by adding
dwc_otg.fiq_fsm_enable=0 dwc_otg.fiq_enable=0 dwc_otg.nak_holdoff=0
to cmdline.txt in /boot
I first tried to use the regular sequence of functions to use.
In the init function:
claim_fiq, set_fiq_regs, enable_fiq
In the exit function
disable_fiq, release_fiq.
But I cannot find which irq number to use, e.g. using irq_of_parse_and_map
I tried several values. 0, 64, but nothing works.
So instead of the enable/disable functions I directly set the timer interrupt
via the IRQFIQ register.
This works; a bit.
The fiq_handler only resets the ARM timer, increments a timer and toggles a LED.
I see the timer counting, the fiq being called.
But the rpi fairly quickly crashes.
In the, sometimes, 10 seconds that it runs I see the led flashing very
irregular.
What is wrong here?
Has the irregularity something to do with suspend/resume?
Please find below the relevant snippets from the init and exit function of the
driver.
And also the fiq_handler.
Thanks in advance,
Sietse
====== init_bat
.....
// directly set ARM timer registers
TIMCNTR = 0x0000000; // stop timer
TIMLOAD = 100000-1; // load value
TIMCINT = 0; // clear interrupt
ret = claim_fiq(&bat_fh);
if (ret) {
printk("batradio: claim_fiq failed.\n");
return ret;
}
set_fiq_handler(&batradio_handler, &batradio_handler_end - &batradio_handler);
regs.ARM_r8 = (long)gpiospi;
regs.ARM_r9 = (long)irqtimer;
regs.ARM_r10 = (long)0;
set_fiq_regs(®s);
TIMCNTR = 0x000000A2; // start timer with interrupt, 23 bit counter
IRQFIQ = 0xC0; // timer interrupt to fiq directly via register
//enable_fiq(64);
....
====== exit_bat
....
IRQFIQ = 0x00; // stop fiq interrupts
TIMCNTR = 0x003E0000; // stop ARM timer
//disable_fiq(64);
....
====== batradio fiq handler
.text
.global batradio_handler
.global batradio_handler_end
batradio_handler:
stmdb sp!, {r6-r7}
mov r6, #0
str r6, [r9, #0x40C] // TIMCINT = 0 // clear interrupt
mov r7, #0x2000 // 1 << CNVST
add r10, r10, #1
ands r6, r10, #0x0001 // set toggle speed
bne off
str r7, [r8, #40] // led on
ldmia sp!, {r6-r7}
subs pc, lr, #4
off: str r7, [r8, #28] // led off
ldmia sp!, {r6-r7}
subs pc, lr, #4
batradio_handler_end:
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