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coresight: sysfs: Increment refcount only for software source

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Except for software sources (e.g. STM), other sources treat multiple
enables as equivalent to a single enable. The device mode already
tracks the binary state, so it is redundant to operate refcount.

Introduce a helper coresight_is_software_source() for check software
source. Refactor to maintain the refcount only for software sources.
This simplifies future CPU PM handling without refcount logic.

Tested-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260515-arm_coresight_path_power_management_improvement-v14-26-f88c4a3ecfe9@arm.com
This commit is contained in:
Leo Yan
2026-05-15 21:08:33 +01:00
committed by Suzuki K Poulose
parent da06d6eb52
commit bf64b06ede
2 changed files with 31 additions and 14 deletions
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39
drivers/hwtracing/coresight/coresight-sysfs.c
View File

@@ -39,6 +39,26 @@ ssize_t coresight_simple_show32(struct device *_dev,
}
EXPORT_SYMBOL_GPL(coresight_simple_show32);
static void coresight_source_get_refcnt(struct coresight_device *csdev)
{
/*
* There could be multiple applications driving the software
* source. So keep the refcount for each such user when the
* source is already enabled.
*
* No need to increment the reference counter for other source
* types, as multiple enables are the same as a single enable.
*/
if (coresight_is_software_source(csdev))
csdev->refcnt++;
}
static void coresight_source_put_refcnt(struct coresight_device *csdev)
{
if (coresight_is_software_source(csdev))
csdev->refcnt--;
}
static int coresight_enable_source_sysfs(struct coresight_device *csdev,
enum cs_mode mode,
struct coresight_path *path)
@@ -57,14 +77,14 @@ static int coresight_enable_source_sysfs(struct coresight_device *csdev,
return ret;
}
csdev->refcnt++;
coresight_source_get_refcnt(csdev);
return 0;
}
/**
* coresight_disable_source_sysfs - Drop the reference count by 1 and disable
* the device if there are no users left.
* coresight_disable_source_sysfs - Drop the reference count by 1 for software
* sources. Disable the device if there are no users left.
*
* @csdev: The coresight device to disable
* @data: Opaque data to pass on to the disable function of the source device.
@@ -79,7 +99,7 @@ static bool coresight_disable_source_sysfs(struct coresight_device *csdev,
if (coresight_get_mode(csdev) != CS_MODE_SYSFS)
return false;
csdev->refcnt--;
coresight_source_put_refcnt(csdev);
if (csdev->refcnt == 0) {
coresight_disable_source(csdev, data);
return true;
@@ -156,9 +176,6 @@ int coresight_enable_sysfs(struct coresight_device *csdev)
int ret = 0;
struct coresight_device *sink;
struct coresight_path *path;
enum coresight_dev_subtype_source subtype;
subtype = csdev->subtype.source_subtype;
mutex_lock(&coresight_mutex);
@@ -173,13 +190,7 @@ int coresight_enable_sysfs(struct coresight_device *csdev)
* doesn't hold coresight_mutex.
*/
if (coresight_get_mode(csdev) == CS_MODE_SYSFS) {
/*
* There could be multiple applications driving the software
* source. So keep the refcount for each such user when the
* source is already enabled.
*/
if (subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE)
csdev->refcnt++;
coresight_source_get_refcnt(csdev);
goto out;
}

6
include/linux/coresight.h
View File

@@ -611,6 +611,12 @@ static inline bool coresight_is_percpu_source(struct coresight_device *csdev)
(csdev->subtype.source_subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_PROC);
}
static inline bool coresight_is_software_source(struct coresight_device *csdev)
{
return csdev && coresight_is_device_source(csdev) &&
(csdev->subtype.source_subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE);
}
static inline bool coresight_is_percpu_sink(struct coresight_device *csdev)
{
return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SINK) &&