Re: [PATCH v2 2/3] coresight: Add support to get preferred id for system trace sources

From: James Clark
Date: Mon Jun 03 2024 - 06:11:09 EST

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In reply to: James Clark: "Re: [PATCH v2 2/3] coresight: Add support to get preferred id for system trace sources"
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On 03/06/2024 11:04, James Clark wrote:
>
>
> On 03/06/2024 10:43, Mao Jinlong wrote:
>> Dynamic trace id was introduced in coresight subsystem, so trace id is
>> allocated dynamically. However, some hardware ATB source has static trace
>> id and it cannot be changed via software programming. For such source,
>> it can call coresight_get_source_traceid to get the fixed trace id from
>> device node and pass id to coresight_trace_id_get_system_id to reserve
>> the id.
>>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
>> ---
>> .../hwtracing/coresight/coresight-platform.c | 26 +++++++++++++++
>> drivers/hwtracing/coresight/coresight-stm.c | 2 +-
>> .../hwtracing/coresight/coresight-trace-id.c | 32 ++++++++++++-------
>> .../hwtracing/coresight/coresight-trace-id.h | 5 ++-
>> include/linux/coresight.h | 1 +
>> 5 files changed, 53 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
>> index 9d550f5697fa..8dd3cbd676b8 100644
>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>> @@ -183,6 +183,17 @@ static int of_coresight_get_cpu(struct device *dev)
>> return cpu;
>> }
>>
>> +/*
>> + * of_coresight_get_trace_id: Get the atid of a source device.
>> + *
>> + * Returns 0 on success.
>> + */
>> +static int of_coresight_get_trace_id(struct device *dev, u32 *id)
>> +{
>> +
>> + return of_property_read_u32(dev->of_node, "trace-id", id);
>> +}
>> +
>> /*
>> * of_coresight_parse_endpoint : Parse the given output endpoint @ep
>> * and fill the connection information in @pdata->out_conns
>> @@ -782,6 +793,12 @@ static inline int acpi_coresight_get_cpu(struct device *dev)
>> {
>> return -ENODEV;
>> }
>> +
>> +static int of_coresight_get_trace_id(struct device *dev, u32 *id)
>> +{
>> + return -ENODEV;
>> +}
>> +
>> #endif
>>
>> int coresight_get_cpu(struct device *dev)
>> @@ -794,6 +811,15 @@ int coresight_get_cpu(struct device *dev)
>> }
>> EXPORT_SYMBOL_GPL(coresight_get_cpu);
>>
>> +int coresight_get_source_traceid(struct device *dev, u32 *id)
>> +{
>> + if (!is_of_node(dev->fwnode))
>> + return -EINVAL;
>> +
>> + return of_coresight_get_trace_id(dev, id);
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_source_traceid);
>> +
>> struct coresight_platform_data *
>> coresight_get_platform_data(struct device *dev)
>> {
>> diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c
>> index e1c62820dfda..802f9e4ae570 100644
>> --- a/drivers/hwtracing/coresight/coresight-stm.c
>> +++ b/drivers/hwtracing/coresight/coresight-stm.c
>> @@ -901,7 +901,7 @@ static int __stm_probe(struct device *dev, struct resource *res)
>> goto stm_unregister;
>> }
>>
>> - trace_id = coresight_trace_id_get_system_id();
>> + trace_id = coresight_trace_id_get_system_id(0);
>
> I would #define 0 to "TRACE_ID_ANY" or something like that so it's
> obvious what it means.
>
>> if (trace_id < 0) {
>> ret = trace_id;
>> goto cs_unregister;
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/drivers/hwtracing/coresight/coresight-trace-id.c
>> index af5b4ef59cea..5c25c75a2f08 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>> @@ -75,20 +75,23 @@ static int coresight_trace_id_find_odd_id(struct coresight_trace_id_map *id_map)
>> * Allocate new ID and set in use
>> *
>> * if @preferred_id is a valid id then try to use that value if available.
>> + * if @only_preferred is true, if @preferred_id is used, return error EINVAL.
>
> if @only_preferred is true @preferred_id must be free, otherwise return
> error -EINVAL
>
>> * if @preferred_id is not valid and @prefer_odd_id is true, try for odd id.
>> *
>> * Otherwise allocate next available ID.
>> */
>> static int coresight_trace_id_alloc_new_id(struct coresight_trace_id_map *id_map,
>> - int preferred_id, bool prefer_odd_id)
>> + int preferred_id, bool prefer_odd_id, bool only_preferred)
>> {
>> int id = 0;
>>
>> /* for backwards compatibility, cpu IDs may use preferred value */
>> - if (IS_VALID_CS_TRACE_ID(preferred_id) &&
>> - !test_bit(preferred_id, id_map->used_ids)) {
>> - id = preferred_id;
>> - goto trace_id_allocated;
>> + if (IS_VALID_CS_TRACE_ID(preferred_id)) {
>> + if (!test_bit(preferred_id, id_map->used_ids)) {
>> + id = preferred_id;
>> + goto trace_id_allocated;
>> + } else if (WARN(only_preferred, "Trace ID %d is used.\n", preferred_id))
>> + return -EINVAL;
>> } else if (prefer_odd_id) {
>> /* may use odd ids to avoid preferred legacy cpu IDs */
>> id = coresight_trace_id_find_odd_id(id_map);
>> @@ -175,7 +178,7 @@ static int coresight_trace_id_map_get_cpu_id(int cpu, struct coresight_trace_id_
>> */
>> id = coresight_trace_id_alloc_new_id(id_map,
>> CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
>> - false);
>> + false, false);
>> if (!IS_VALID_CS_TRACE_ID(id))
>> goto get_cpu_id_out_unlock;
>>
>> @@ -222,14 +225,21 @@ static void coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
>> DUMP_ID_MAP(id_map);
>> }
>>
>> -static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map)
>> +static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map,
>> + int preferred_id, bool only_preferred)
>
> Looks like "only_preferred" was left on here by mistake and it's not
> used. For this function preferred_id != 0 means the same.
>
>> {
>> unsigned long flags;
>> int id;
>>
>> spin_lock_irqsave(&id_map_lock, flags);
>> - /* prefer odd IDs for system components to avoid legacy CPU IDS */
>> - id = coresight_trace_id_alloc_new_id(id_map, 0, true);
>> +
>> + if (preferred_id > 0) {
>> + /* use preferred id if it is available */
>> + id = coresight_trace_id_alloc_new_id(id_map, preferred_id, false, true);
>> + } else {
>> + /* prefer odd IDs for system components to avoid legacy CPU IDS */
>> + id = coresight_trace_id_alloc_new_id(id_map, 0, true, false);
>
> prefer_odd_id is different in each of these calls which I think is a
> mistake?
>
> You could do one function call to avoid that:
>
> only_preferred = preferred_id > 0
> coresight_trace_id_alloc_new_id(id_map, preferred_id, true,
> only_preferred);
>
>

Actually, even better we can have an "int flags" argument rather than
having to work out what a load of booleans mean. And then use these:

TRACE_ID_WANT_ODD | TRACE_ID_WANT_PREFERRED

flags = TRACE_ID_WANT_ODD
flags |= preferred_id > 0 ? TRACE_ID_WANT_PREFERRED : 0;
coresight_trace_id_alloc_new_id(id_map, preferred_id, flags);

>> + }
>> spin_unlock_irqrestore(&id_map_lock, flags);
>>
>> DUMP_ID(id);
>> @@ -269,9 +279,9 @@ int coresight_trace_id_read_cpu_id(int cpu)
>> }
>> EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
>>
>> -int coresight_trace_id_get_system_id(void)
>> +int coresight_trace_id_get_system_id(int id)
>> {
>> - return coresight_trace_id_map_get_system_id(&id_map_default);
>> + return coresight_trace_id_map_get_system_id(&id_map_default, id, true);
>> }
>> EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/drivers/hwtracing/coresight/coresight-trace-id.h
>> index 3797777d367e..9189a33c5857 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
>> @@ -118,9 +118,12 @@ int coresight_trace_id_read_cpu_id(int cpu);
>> *
>> * Used to allocate IDs for system trace sources such as STM.
>> *
>> + * @id: Preferred id value. If id is 0, get a free id from id map. If id is greater
>
> 0 -> TRACE_ID_ANY
>
>> + * than 0, get a preferred id.
>> + *
>> * return: Trace ID or -EINVAL if allocation is impossible.
>> */
>> -int coresight_trace_id_get_system_id(void);
>> +int coresight_trace_id_get_system_id(int id);
>>
>> /**
>> * Release an allocated system trace ID.
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index f09ace92176e..0599303be326 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct coresight_device *csdev,
>> void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset);
>>
>> extern int coresight_get_cpu(struct device *dev);
>> +extern int coresight_get_source_traceid(struct device *dev, u32 *id);
>>
>> struct coresight_platform_data *coresight_get_platform_data(struct device *dev);
>> struct coresight_connection *

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