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Message-ID: <CAJ9a7VjVfdDMJXMG0nosFrorYK8FmbXAa2qDhO6QuGp4H3+Q8g@mail.gmail.com>
Date: Wed, 9 Feb 2022 15:34:30 +0000
From: Mike Leach <mike.leach@...aro.org>
To: Mao Jinlong <quic_jinlmao@...cinc.com>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Leo Yan <leo.yan@...aro.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
Tingwei Zhang <quic_tingweiz@...cinc.com>,
Yuanfang Zhang <quic_yuanfang@...cinc.com>,
Tao Zhang <quic_taozha@...cinc.com>,
Trilok Soni <quic_tsoni@...cinc.com>,
Hao Zhang <quic_hazha@...cinc.com>,
linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 01/10] Use IDR to maintain all the enabled sources' paths.
Hi,
On Wed, 9 Feb 2022 at 10:57, Mao Jinlong <quic_jinlmao@...cinc.com> wrote:
>
> Use hash length of the source's device name to map to the pointer
> of the enabled path. Using IDR will be more efficient than using
> the list. And there could be other sources except STM and CPU etms
> in the new HWs. It is better to maintain all the paths together.
>
> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
> ---
> drivers/hwtracing/coresight/coresight-core.c | 76 +++++++-------------
> 1 file changed, 27 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 88653d1c06a4..a90097f88425 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -7,6 +7,7 @@
> #include <linux/init.h>
> #include <linux/types.h>
> #include <linux/device.h>
> +#include <linux/idr.h>
> #include <linux/io.h>
> #include <linux/err.h>
> #include <linux/export.h>
> @@ -26,6 +27,12 @@
> static DEFINE_MUTEX(coresight_mutex);
> static DEFINE_PER_CPU(struct coresight_device *, csdev_sink);
>
> +/*
> + * Use IDR to map the hash length of the source's device name
> + * to the pointer of path for the source
> + */
> +static DEFINE_IDR(path_idr);
> +
> /**
> * struct coresight_node - elements of a path, from source to sink
> * @csdev: Address of an element.
> @@ -36,20 +43,6 @@ struct coresight_node {
> struct list_head link;
> };
>
> -/*
> - * When operating Coresight drivers from the sysFS interface, only a single
> - * path can exist from a tracer (associated to a CPU) to a sink.
> - */
> -static DEFINE_PER_CPU(struct list_head *, tracer_path);
> -
> -/*
> - * As of this writing only a single STM can be found in CS topologies. Since
> - * there is no way to know if we'll ever see more and what kind of
> - * configuration they will enact, for the time being only define a single path
> - * for STM.
> - */
> -static struct list_head *stm_path;
> -
> /*
> * When losing synchronisation a new barrier packet needs to be inserted at the
> * beginning of the data collected in a buffer. That way the decoder knows that
> @@ -1088,10 +1081,11 @@ static int coresight_validate_source(struct coresight_device *csdev,
>
> int coresight_enable(struct coresight_device *csdev)
> {
> - int cpu, ret = 0;
> + int ret = 0;
> struct coresight_device *sink;
> struct list_head *path;
> enum coresight_dev_subtype_source subtype;
> + u32 hash;
>
> subtype = csdev->subtype.source_subtype;
>
> @@ -1133,26 +1127,14 @@ int coresight_enable(struct coresight_device *csdev)
> if (ret)
> goto err_source;
>
> - switch (subtype) {
> - case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
> - /*
> - * When working from sysFS it is important to keep track
> - * of the paths that were created so that they can be
> - * undone in 'coresight_disable()'. Since there can only
> - * be a single session per tracer (when working from sysFS)
> - * a per-cpu variable will do just fine.
> - */
> - cpu = source_ops(csdev)->cpu_id(csdev);
> - per_cpu(tracer_path, cpu) = path;
> - break;
> - case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
> - stm_path = path;
> - break;
> - default:
> - /* We can't be here */
> - break;
> - }
> -
> + /*
> + * Use the hash length of source's device name as ID
Slightly confusing comment:
hashlen_string creates a hash and a length for the string. We are
using the hash here so comment should be:
"Use the hash of source's device name as ID"
> + * and map the ID to the pointer of the path.
> + */
> + hash = hashlen_hash(hashlen_string(NULL, dev_name(&csdev->dev)));
> + ret = idr_alloc_u32(&path_idr, path, &hash, hash, GFP_KERNEL);
> + if (ret)
> + goto err_source;
> out:
> mutex_unlock(&coresight_mutex);
> return ret;
> @@ -1168,8 +1150,9 @@ EXPORT_SYMBOL_GPL(coresight_enable);
>
> void coresight_disable(struct coresight_device *csdev)
> {
> - int cpu, ret;
> + int ret;
> struct list_head *path = NULL;
> + u32 hash;
>
> mutex_lock(&coresight_mutex);
>
> @@ -1180,21 +1163,16 @@ void coresight_disable(struct coresight_device *csdev)
> if (!csdev->enable || !coresight_disable_source(csdev))
> goto out;
>
> - switch (csdev->subtype.source_subtype) {
> - case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
> - cpu = source_ops(csdev)->cpu_id(csdev);
> - path = per_cpu(tracer_path, cpu);
> - per_cpu(tracer_path, cpu) = NULL;
> - break;
> - case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
> - path = stm_path;
> - stm_path = NULL;
> - break;
> - default:
> - /* We can't be here */
> - break;
> + hash = hashlen_hash(hashlen_string(NULL, dev_name(&csdev->dev)));
> + /* Find the path by the hash length. */
same comment as above re hash / hash length
> + path = idr_find(&path_idr, hash);
> + if (path == NULL) {
> + dev_info(&csdev->dev, "Path is not found for %s\n",
> + dev_name(&csdev->dev));
pr_err() is used in other parts of this file to print error messages.
> + return;
this skips the mutex_unlock(). use goto out;
> }
>
> + idr_remove(&path_idr, hash);
> coresight_disable_path(path);
> coresight_release_path(path);
>
> --
> 2.17.1
>
Regards
Mike
--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK
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