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Message-ID: <20211028180659.GC4045120@p14s>
Date: Thu, 28 Oct 2021 12:06:59 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Tao Zhang <quic_taozha@...cinc.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Mike Leach <mike.leach@...aro.org>,
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>,
Mao Jinlong <quic_jinlmao@...cinc.com>,
Yuanfang Zhang <quic_yuanfang@...cinc.com>,
Trilok Soni <quic_tsoni@...cinc.com>,
Tingwei Zhang <tingwei@...eaurora.org>
Subject: Re: [PATCH 01/10] coresight: add support to enable more coresight
paths
On Thu, Oct 21, 2021 at 03:38:47PM +0800, Tao Zhang wrote:
> Current coresight implementation only supports enabling source
> ETMs or STM. This patch adds support to enable more kinds of
> coresight source to sink paths. We build a path from source to
> sink when any source is enabled and store it in a list. When the
> source is disabled, we fetch the corresponding path from the list
> and decrement the refcount on each device in the path. The device
> is disabled if the refcount reaches zero. Don't store path to
> coresight data structure of source to avoid unnecessary change to
> ABI.
> Since some targets may have coresight sources other than STM and
> ETMs, we need to add this change to support these coresight
> devices.
>
> Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> ---
> drivers/hwtracing/coresight/coresight-core.c | 100 +++++++++++--------
> 1 file changed, 56 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 8a18c71df37a..1e621d61307a 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -37,18 +37,16 @@ struct coresight_node {
> };
>
> /*
> - * When operating Coresight drivers from the sysFS interface, only a single
> - * path can exist from a tracer (associated to a CPU) to a sink.
> + * struct coresight_path - path from source to sink
> + * @path: Address of path list.
> + * @link: hook to the list.
> */
> -static DEFINE_PER_CPU(struct list_head *, tracer_path);
> +struct coresight_path {
> + struct list_head *path;
> + struct list_head link;
> +};
For sources associated with a CPU, like ETMs, having a per-cpu way of storing
paths is a definite advantage and should be kept that way.
>
> -/*
> - * 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;
> +static LIST_HEAD(cs_active_paths);
Then there are sources that aren't associated with a CPU like STMs and TPDMs.
Perhaps using an IDR or the hash of the device name as a key to a hashing
vector would be better than doing a sequential search, especially as the
list of devices is bound to increase over time.
>
> /*
> * When losing synchronisation a new barrier packet needs to be inserted at the
> @@ -354,6 +352,7 @@ static void coresight_disable_sink(struct coresight_device *csdev)
> if (ret)
> return;
> coresight_control_assoc_ectdev(csdev, false);
> + csdev->activated = false;
I don't see why this is needed and without proper documentation there is no way
for me to guess the logic behind the change. The ->activated flag should be
manipulated from the command line interface only.
> csdev->enable = false;
> }
>
> @@ -590,6 +589,20 @@ int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data)
> goto out;
> }
>
> +static struct coresight_device *coresight_get_source(struct list_head *path)
> +{
> + struct coresight_device *csdev;
> +
> + if (!path)
> + return NULL;
> +
> + csdev = list_first_entry(path, struct coresight_node, link)->csdev;
> + if (csdev->type != CORESIGHT_DEV_TYPE_SOURCE)
> + return NULL;
> +
> + return csdev;
> +}
> +
> struct coresight_device *coresight_get_sink(struct list_head *path)
> {
> struct coresight_device *csdev;
> @@ -1086,9 +1099,23 @@ static int coresight_validate_source(struct coresight_device *csdev,
> return 0;
> }
>
> +static int coresight_store_path(struct list_head *path)
> +{
> + struct coresight_path *node;
> +
> + node = kzalloc(sizeof(struct coresight_path), GFP_KERNEL);
> + if (!node)
> + return -ENOMEM;
> +
> + node->path = path;
> + list_add(&node->link, &cs_active_paths);
> +
> + return 0;
> +}
> +
> 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;
> @@ -1133,25 +1160,9 @@ 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;
> - }
> + ret = coresight_store_path(path);
> + if (ret)
> + goto err_source;
>
> out:
> mutex_unlock(&coresight_mutex);
> @@ -1168,8 +1179,11 @@ EXPORT_SYMBOL_GPL(coresight_enable);
>
> void coresight_disable(struct coresight_device *csdev)
> {
> - int cpu, ret;
> + int ret;
> struct list_head *path = NULL;
> + struct coresight_path *cspath = NULL;
> + struct coresight_path *cspath_next = NULL;
> + struct coresight_device *src_csdev = NULL;
>
> mutex_lock(&coresight_mutex);
>
> @@ -1180,20 +1194,18 @@ 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;
> + list_for_each_entry_safe(cspath, cspath_next, &cs_active_paths, link) {
> + src_csdev = coresight_get_source(cspath->path);
> + if (!src_csdev)
> + continue;
> + if (src_csdev == csdev) {
> + path = cspath->path;
> + list_del(&cspath->link);
> + kfree(cspath);
See my comment above - I agree that sources _not_ associated with a CPU should
be handled differently. CPU bound sources should be kept untouched.
That is all the time I had for today, I will continue tomorrow.
Thanks,
Mathieu
> + }
> }
> + if (path == NULL)
> + goto out;
>
> coresight_disable_path(path);
> coresight_release_path(path);
> --
> 2.17.1
>
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