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| author |   Mathieu Poirier <mathieu.poirier@linaro.org> | 2019-04-25 13:52:56 -0600 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-25 22:00:16 +0200 |
| commit | f973d88b75703719d39c4d5145079199aaf442b2 (patch) | |
| tree | 3abbbcce4aa7204d7584b3bcfaca818f910d7a63 /drivers/hwtracing/coresight/coresight-tpiu.c | |
| parent | coresight: Adding return code to sink::disable() operation (diff) | |
| download | linux-dev-f973d88b75703719d39c4d5145079199aaf442b2.tar.xz linux-dev-f973d88b75703719d39c4d5145079199aaf442b2.zip | |
coresight: Move reference counting inside sink drivers
When operating in CPU-wide mode with an N:1 source/sink HW topology,
multiple CPUs can access a sink concurrently. As such reference counting
needs to happen when the device's spinlock is held to avoid racing with
other operations (start(), update(), stop()), such as:
session A Session B
----- -------
enable_sink
atomic_inc(refcount) = 1
...
atomic_dec(refcount) = 0 enable_sink
if (refcount == 0) disable_sink
atomic_inc()
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Robert Walker <robert.walker@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hwtracing/coresight/coresight-tpiu.c')
| -rw-r--r-- | drivers/hwtracing/coresight/coresight-tpiu.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c index c1b77e3c3187..63d9af31f57f 100644 --- a/drivers/hwtracing/coresight/coresight-tpiu.c +++ b/drivers/hwtracing/coresight/coresight-tpiu.c @@ -5,6 +5,7 @@ * Description: CoreSight Trace Port Interface Unit driver */ +#include <linux/atomic.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/device.h> @@ -73,7 +74,7 @@ static int tpiu_enable(struct coresight_device *csdev, u32 mode, void *__unused) struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); tpiu_enable_hw(drvdata); - + atomic_inc(csdev->refcnt); dev_dbg(drvdata->dev, "TPIU enabled\n"); return 0; } @@ -98,6 +99,9 @@ static int tpiu_disable(struct coresight_device *csdev) { struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); + if (atomic_dec_return(csdev->refcnt)) + return -EBUSY; + tpiu_disable_hw(drvdata); dev_dbg(drvdata->dev, "TPIU disabled\n"); |