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SubjectRe: [PATCH v2 1/9] Use IDR to maintain all the enabled sources' paths.
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Hi Mathieu,

Thanks for the review.

On 12/15/2021 2:30 AM, Mathieu Poirier wrote:
> Hi Mao,
>
> On Thu, Dec 09, 2021 at 10:15:35PM +0800, Mao Jinlong 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@quicinc.com>
>> ---
>> drivers/hwtracing/coresight/coresight-core.c | 76 +++++++-------------
>> 1 file changed, 26 insertions(+), 50 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
>> index 8a18c71df37a..cc6b6cabf85f 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
>> + * 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 +1163,13 @@ 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. */
>> + path = idr_find(&path_idr, hash);
>> + if (path == NULL)
>> + return;
> Please add a dev_err() here as this should really not be happening.

I will add the dev_err().

>
>>
>> + idr_remove(&path_idr, hash);
>> coresight_disable_path(path);
>> coresight_release_path(path);
>>
>> @@ -1779,6 +1754,7 @@ static int __init coresight_init(void)
>>
>> static void __exit coresight_exit(void)
>> {
>> + idr_destroy(&path_idr);
> As far as I can tell this isn't needed.

I will remove this.

>
>> cscfg_exit();
>> etm_perf_exit();
>> bus_unregister(&coresight_bustype);
>> --
>> 2.17.1
>>

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