Updating kernel on my board caused crashes while using a MPU6050, more
specifically when enabling its trigger. This seems due to commit
5ec6486daa98 ("iio:imu: inv_mpu6050: support more interrupt types").
Since the said commit, the MPU6050 driver supports also level-triggered
interrupts, other than rising-edge interrupts. Unfortunately
level-triggered interrupts don't work here [0] causing IRQ floods [1],
Oopses [2] and crashes. This even affected a previously-working setup [3].
I have to say that I'm not honestly completely sure how to interpret my
Oopses, and that they are also pointing to the I2C controller and to the
serial tty driver somehow. However I think that there is a real problem
with the said IIO commit anyway; support for level-triggered IRQs seems
broken to me due to the following reason:
The handler for MPU6050 hardware IRQ is iio_trigger_generic_data_rdy_poll()
which doesn't acknowleges the IRQ (i.e. the IRQ line remains asserted); the
IRQ is acknowledged only in the bottom half of the IIO softIRQ, registered
with devm_iio_triggered_buffer_setup(), which is inv_mpu6050_read_fifo().
I think that in this way the hardware IRQ is re-enabled before the IRQ is
acknowledged to the IMU. When the IRQ is level-triggered, the IRQ line
remains asserted causing the hardware IRQ handler to be reentered,
generating a (fake) IRQ storm (while when interrupts are edge-triggered the
IMU just generate one pulse until acknowledgment, I guess).
Just adding IRQF_ONESHOT to the hardware IRQ flags apparently doesn't make
any difference, because it would just defer the IRQ re-enable to the bottom
half of the very same (hardware) IRQ handler, while, in my understanding,
here the interrupt acknowledgment happens in the bottom half of the *soft*
IRQ, which is another IRQ indeed.
The following PoC patch moves the interrupt status register read (which
also acknowledges the IRQ) to the bottom half of the *hardware* IRQ
handler, which now becomes a threaded IRQ with the IRQF_ONESHOT flag.
This seems to work. The softirq handler doesn't hopefully really need to
look at the interrupt status register because it will give up early anyway
when it finds no data in the IMU FIFO.
I have to say that I'm not really sure this is a good way to fix things;
possibly someone has advices for a better fix (RFC).
In case this fix turns out to be not adequate, and no-one has a better one,
then I'd propose to revert the level-triggered interrupt support (and maybe
make the probe failing whenever an unsupported IRQ type is requested?).
[0] Here I'm on a custom board with a Zynq7000 SoC (IRQ controller supports
both raising-edge and level IRQ) and an MPU9250 IMU. I've done most work on
a 5.15 customized kernel, but I've tried also with latest mainline tree and
I got the same results.
[1] when running:
root@arm:/sys/bus/iio/devices/iio:device2/buffer0# echo 1 > enable ; sleep 5; echo 0 > enable
on a 5.15 kernel the system somehow survived, despite Oopses and
complaints, so I could give a look to /proc/interrupts:
64: 1119991 0 GIC-0 68 Level inv_mpu
65: 55 0 mpu9250-dev2 Edge mpu9250_consumer2
The hardware IRQ counted an unreasonably huge number of interrupts, while
the trigger softirq counted a reasonable number of interrupts.
(On a working system i.e. before the blamed commit, or after my patch,
these two counters count the same number of IRQs)
[2] Depending by a number of factors (e.g. RT-patch, kernel debug
configuration options, kernel version) I got some different complaints. The
following is the one I grabbed from the latest git tree kernel.
(irq/47-41620000/45 refers to the I2C controller to witch the IMU is
attached to):
[ 250.941155] sched: RT throttling activated
[ 275.557147] rcu: INFO: rcu_sched self-detected stall on CPU
[ 275.562749] rcu: 0-....: (26689 ticks this GP) idle=89dc/1/0x40000002 softirq=20591/20592 fqs=6234
[ 275.563143]
[ 275.563148] =============================
[ 275.563152] [ BUG: Invalid wait context ]
[ 275.563156] 6.5.0-rc3+ #17 Not tainted
[ 275.563163] -----------------------------
[ 275.563166] irq/47-41620000/45 is trying to lock:
[ 275.563173] c20ff850 (&port_lock_key){-.-.}-{3:3}, at: cdns_uart_console_write+0x130/0x164
[ 275.563226] other info that might help us debug this:
[ 275.563230] context-{3:3}
[ 275.563235] 4 locks held by irq/47-41620000/45:
[ 275.563242] #0: c147d510 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0x87c/0x12f0
[ 275.563285] #1: c1416b30 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x100/0x320
[ 275.563327] #2: c1416b98 (console_srcu){....}-{0:0}, at: console_flush_all+0x68/0x664
[ 275.563361] #3: c1416c24 (console_owner){-.-.}-{0:0}, at: console_flush_all+0x1c4/0x664
[ 275.563395] stack backtrace:
[ 275.563399] CPU: 0 PID: 45 Comm: irq/47-41620000 Not tainted 6.5.0-rc3+ #17
[ 275.563412] Hardware name: Xilinx Zynq Platform
[ 275.563420] unwind_backtrace from show_stack+0x10/0x14
[ 275.563450] show_stack from dump_stack_lvl+0x68/0x90
[ 275.563474] dump_stack_lvl from __lock_acquire+0x61c/0x1778
[ 275.563494] __lock_acquire from lock_acquire+0x1e4/0x368
[ 275.563512] lock_acquire from _raw_spin_lock_irqsave+0x54/0x68
[ 275.563534] _raw_spin_lock_irqsave from cdns_uart_console_write+0x130/0x164
[ 275.563564] cdns_uart_console_write from console_flush_all+0x220/0x664
[ 275.563595] console_flush_all from console_unlock+0x88/0xd4
[ 275.563624] console_unlock from vprintk_emit+0x25c/0x320
[ 275.563653] vprintk_emit from vprintk_default+0x20/0x28
[ 275.563682] vprintk_default from _printk+0x30/0x54
[ 275.563715] _printk from print_cpu_stall_info+0x2b0/0x490
[ 275.563742] print_cpu_stall_info from rcu_sched_clock_irq+0x890/0x12f0
[ 275.563766] rcu_sched_clock_irq from update_process_times+0x54/0x8c
[ 275.563793] update_process_times from tick_sched_timer+0x50/0xac
[ 275.563825] tick_sched_timer from __hrtimer_run_queues+0x2f0/0x598
[ 275.563851] __hrtimer_run_queues from hrtimer_interrupt+0x130/0x2ac
[ 275.563873] hrtimer_interrupt from twd_handler+0x30/0x38
[ 275.563897] twd_handler from handle_percpu_devid_irq+0xb0/0x2b4
[ 275.563928] handle_percpu_devid_irq from generic_handle_domain_irq+0x24/0x34
[ 275.563950] generic_handle_domain_irq from gic_handle_irq+0x84/0xac
[ 275.563981] gic_handle_irq from generic_handle_arch_irq+0x34/0x44
[ 275.564009] generic_handle_arch_irq from call_with_stack+0x18/0x20
[ 275.564032] call_with_stack from __irq_svc+0x9c/0xb8
[ 275.564048] Exception stack(0xf0935e48 to 0xf0935e90)
[ 275.564062] 5e40: ffffffff ffffffff 00000001 00000403 ef7cb080 00000000
[ 275.564074] 5e60: c1be107c c4b01040 d1377d58 2e465000 c0d4b0d8 f0935ed4 00000000 f0935e98
[ 275.564082] 5e80: c015a054 c015a058 600f0013 ffffffff
[ 275.564089] __irq_svc from finish_task_switch+0xe4/0x2b4
[ 275.564119] finish_task_switch from __schedule+0x394/0xd9c
[ 275.564149] __schedule from schedule+0x60/0xbc
[ 275.564176] schedule from irq_thread+0xd0/0x238
[ 275.564201] irq_thread from kthread+0xf4/0x12c
[ 275.564231] kthread from ret_from_fork+0x14/0x28
[ 275.564251] Exception stack(0xf0935fb0 to 0xf0935ff8)
[ 275.564261] 5fa0: 00000000 00000000 00000000 00000000
[ 275.564271] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 275.564280] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 275.886419] rcu: hardirqs softirqs csw/system
[ 275.891989] rcu: number: 2641898 0 0
[ 275.897561] rcu: cputime: 0 0 12997 ==> 13007(ms)
[ 275.904523] rcu: (t=26010 jiffies g=36053 q=115 ncpus=2)
[ 275.909924] CPU: 0 PID: 45 Comm: irq/47-41620000 Not tainted 6.5.0-rc3+ #17
[ 275.916891] Hardware name: Xilinx Zynq Platform
[ 275.921413] PC is at finish_task_switch+0xe4/0x2b4
[ 275.926213] LR is at finish_task_switch+0xe0/0x2b4
[ 275.931013] pc : [<c015a058>] lr : [<c015a054>] psr: 600f0013
[ 275.937280] sp : f0935e98 ip : 00000000 fp : f0935ed4
[ 275.942505] r10: c0d4b0d8 r9 : 2e465000 r8 : d1377d58
[ 275.947722] r7 : c4b01040 r6 : c1be107c r5 : 00000000 r4 : ef7cb080
[ 275.954249] r3 : 00000403 r2 : 00000001 r1 : ffffffff r0 : ffffffff
[ 275.960777] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
[ 275.967914] Control: 18c5387d Table: 04b8404a DAC: 00000051
[ 275.973661] finish_task_switch from __schedule+0x394/0xd9c
[ 275.979258] __schedule from schedule+0x60/0xbc
[ 275.983806] schedule from irq_thread+0xd0/0x238
[ 275.988442] irq_thread from kthread+0xf4/0x12c
[ 275.992990] kthread from ret_from_fork+0x14/0x28
[ 275.997702] Exception stack(0xf0935fb0 to 0xf0935ff8)
[ 276.002757] 5fa0: 00000000 00000000 00000000 00000000
[ 276.010936] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 276.019110] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[3] Previously, even if the DT node configured the IRQ as level-triggered,
the MPU9060 driver changed it to edge-triggered, because it was the only
supported mode. This made things working in my case. Now with the very same
DT the IRQ is configured as level (which in principle should be correct)
but things stopped working indeed.
Signed-off-by: Andrea Merello <andrea.merello@xxxxxx>
---
drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 11 -------
drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c | 31 ++++++++++++++++---
2 files changed, 26 insertions(+), 16 deletions(-)
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
index 45c37525c2f1..b87ca50dc1c1 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
@@ -122,21 +122,10 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
int result;
u16 fifo_count;
s64 timestamp;
- int int_status;
size_t i, nb;
mutex_lock(&st->lock);
- /* ack interrupt and check status */
- result = regmap_read(st->map, st->reg->int_status, &int_status);
- if (result) {
- dev_err(regmap_get_device(st->map),
- "failed to ack interrupt\n");
- goto flush_fifo;
- }
- if (!(int_status & INV_MPU6050_BIT_RAW_DATA_RDY_INT))
- goto end_session;
-
if (!(st->chip_config.accl_fifo_enable |
st->chip_config.gyro_fifo_enable |
st->chip_config.magn_fifo_enable))
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
index 882546897255..b1384d729ced 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
@@ -217,6 +217,26 @@ static const struct iio_trigger_ops inv_mpu_trigger_ops = {
.set_trigger_state = &inv_mpu_data_rdy_trigger_set_state,
};
+irqreturn_t inv_mpu6050_trigger_irq(int irq, void *private)
+{
+ struct inv_mpu6050_state *st = private;
+
+ iio_trigger_generic_data_rdy_poll(irq, st->trig);
+ return IRQ_WAKE_THREAD;
+}
+
+irqreturn_t inv_mpu6050_trigger_thread_fn(int irq, void *private)
+{
+ struct inv_mpu6050_state *st = private;
+ int int_status;
+
+ mutex_lock(&st->lock);
+ regmap_read(st->map, st->reg->int_status, &int_status);
+ mutex_unlock(&st->lock);
+
+ return IRQ_HANDLED;
+}
+
int inv_mpu6050_probe_trigger(struct iio_dev *indio_dev, int irq_type)
{
int ret;
@@ -229,11 +249,12 @@ int inv_mpu6050_probe_trigger(struct iio_dev *indio_dev, int irq_type)
if (!st->trig)
return -ENOMEM;
- ret = devm_request_irq(&indio_dev->dev, st->irq,
- &iio_trigger_generic_data_rdy_poll,
- irq_type,
- "inv_mpu",
- st->trig);
+ ret = devm_request_threaded_irq(&indio_dev->dev, st->irq,
+ &inv_mpu6050_trigger_irq,
+ &inv_mpu6050_trigger_thread_fn,
+ irq_type | IRQF_ONESHOT,
+ "inv_mpu",
+ st);
if (ret)
return ret;
--
2.17.1
