summaryrefslogtreecommitdiffstats
path: root/drivers/iio
diff options
context:
space:
mode:
authorXander Huff <xander.huff@ni.com>2015-08-11 18:00:49 -0500
committerJonathan Cameron <jic23@kernel.org>2015-08-16 10:51:27 +0100
commit70581e0ef8634074cc305f9e63e8abec08788753 (patch)
tree5c9864d0febc2aa9dd81eb466d7426365d3ef100 /drivers/iio
parent70b2737e0a948552843ce1b8500e033080677086 (diff)
downloadlinux-70581e0ef8634074cc305f9e63e8abec08788753.tar.bz2
iio: adc: xilinx-xadc: Push interrupts into hardirq context
The driver currently registers a pair of irq handlers using request_threaded_irq(), however the synchronization mechanism between the hardirq and the threadedirq handler is a regular spinlock. Unfortunately, this breaks PREEMPT_RT builds, where a spinlock can sleep, and is thus not able to be acquired from a hardirq handler. This patch gets rid of the threaded handler and pushes all interrupt handling into the hardirq context, and uses request_irq(). To validate that this change has no impact on RT performance, here are cyclictest values with no processes running: $ sudo cyclictest -S -m -p 98 policy: fifo: loadavg: 0.00 0.01 0.05 1/174 2539 T: 0 ( 1405) P:98 I:1000 C:167010520 Min: 9 Act: 12 Avg: 12 Max: 75 T: 1 ( 1862) P:98 I:1500 C:111340339 Min: 9 Act: 12 Avg: 12 Max: 73 Then, all xadc raw handles were accessed in a continuous loop via /sys/bus/iio/devices/iio:device0: $ sudo cyclictest -S -m -p 98 policy: fifo: loadavg: 7.84 7.70 7.63 3/182 4260 T: 0 ( 2559) P:98 I:1000 C:241557018 Min: 11 Act: 18 Avg: 21 Max: 74 T: 1 ( 2560) P:98 I:1500 C:161038006 Min: 10 Act: 21 Avg: 20 Max: 73 Signed-off-by: Xander Huff <xander.huff@ni.com> Acked-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers/iio')
-rw-r--r--drivers/iio/adc/xilinx-xadc-core.c37
-rw-r--r--drivers/iio/adc/xilinx-xadc.h2
2 files changed, 10 insertions, 29 deletions
diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
index ce93bd8e3f68..0370624a35db 100644
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -273,33 +273,13 @@ static void xadc_zynq_unmask_worker(struct work_struct *work)
schedule_delayed_work(&xadc->zynq_unmask_work,
msecs_to_jiffies(XADC_ZYNQ_UNMASK_TIMEOUT));
}
-}
-
-static irqreturn_t xadc_zynq_threaded_interrupt_handler(int irq, void *devid)
-{
- struct iio_dev *indio_dev = devid;
- struct xadc *xadc = iio_priv(indio_dev);
- unsigned int alarm;
-
- spin_lock_irq(&xadc->lock);
- alarm = xadc->zynq_alarm;
- xadc->zynq_alarm = 0;
- spin_unlock_irq(&xadc->lock);
-
- xadc_handle_events(indio_dev, xadc_zynq_transform_alarm(alarm));
- /* unmask the required interrupts in timer. */
- schedule_delayed_work(&xadc->zynq_unmask_work,
- msecs_to_jiffies(XADC_ZYNQ_UNMASK_TIMEOUT));
-
- return IRQ_HANDLED;
}
static irqreturn_t xadc_zynq_interrupt_handler(int irq, void *devid)
{
struct iio_dev *indio_dev = devid;
struct xadc *xadc = iio_priv(indio_dev);
- irqreturn_t ret = IRQ_HANDLED;
uint32_t status;
xadc_read_reg(xadc, XADC_ZYNQ_REG_INTSTS, &status);
@@ -321,18 +301,23 @@ static irqreturn_t xadc_zynq_interrupt_handler(int irq, void *devid)
status &= XADC_ZYNQ_INT_ALARM_MASK;
if (status) {
- xadc->zynq_alarm |= status;
xadc->zynq_masked_alarm |= status;
/*
* mask the current event interrupt,
* unmask it when the interrupt is no more active.
*/
xadc_zynq_update_intmsk(xadc, 0, 0);
- ret = IRQ_WAKE_THREAD;
+
+ xadc_handle_events(indio_dev,
+ xadc_zynq_transform_alarm(status));
+
+ /* unmask the required interrupts in timer. */
+ schedule_delayed_work(&xadc->zynq_unmask_work,
+ msecs_to_jiffies(XADC_ZYNQ_UNMASK_TIMEOUT));
}
spin_unlock(&xadc->lock);
- return ret;
+ return IRQ_HANDLED;
}
#define XADC_ZYNQ_TCK_RATE_MAX 50000000
@@ -437,7 +422,6 @@ static const struct xadc_ops xadc_zynq_ops = {
.setup = xadc_zynq_setup,
.get_dclk_rate = xadc_zynq_get_dclk_rate,
.interrupt_handler = xadc_zynq_interrupt_handler,
- .threaded_interrupt_handler = xadc_zynq_threaded_interrupt_handler,
.update_alarm = xadc_zynq_update_alarm,
};
@@ -1225,9 +1209,8 @@ static int xadc_probe(struct platform_device *pdev)
if (ret)
goto err_free_samplerate_trigger;
- ret = request_threaded_irq(irq, xadc->ops->interrupt_handler,
- xadc->ops->threaded_interrupt_handler,
- 0, dev_name(&pdev->dev), indio_dev);
+ ret = request_irq(irq, xadc->ops->interrupt_handler, 0,
+ dev_name(&pdev->dev), indio_dev);
if (ret)
goto err_clk_disable_unprepare;
diff --git a/drivers/iio/adc/xilinx-xadc.h b/drivers/iio/adc/xilinx-xadc.h
index 54adc5087210..f6f081965647 100644
--- a/drivers/iio/adc/xilinx-xadc.h
+++ b/drivers/iio/adc/xilinx-xadc.h
@@ -60,7 +60,6 @@ struct xadc {
enum xadc_external_mux_mode external_mux_mode;
- unsigned int zynq_alarm;
unsigned int zynq_masked_alarm;
unsigned int zynq_intmask;
struct delayed_work zynq_unmask_work;
@@ -79,7 +78,6 @@ struct xadc_ops {
void (*update_alarm)(struct xadc *, unsigned int);
unsigned long (*get_dclk_rate)(struct xadc *);
irqreturn_t (*interrupt_handler)(int, void *);
- irqreturn_t (*threaded_interrupt_handler)(int, void *);
unsigned int flags;
};