Re: [PATCH v6 2/3] coresight: Add support to get static id for system trace sources

[Jinlong Mao <quic_jinlmao@quicinc.com>]

On 2024/11/13 21:27, Suzuki K Poulose wrote:
> On 04/11/2024 11:56, 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_static_trace_id to get the fixed trace id from
>> device node and pass id to coresight_trace_id_get_static_system_id to
>> reserve the id.
>>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>> Reviewed-by: Mike Leach <mike.leach@linaro.org>
>> ---
>>   .../hwtracing/coresight/coresight-platform.c  |  6 +++
>>   .../hwtracing/coresight/coresight-trace-id.c  | 39 +++++++++++++------
>>   .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
>>   include/linux/coresight.h                     |  1 +
>>   4 files changed, 44 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/ 
>> drivers/hwtracing/coresight/coresight-platform.c
>> index 64e171eaad82..633d96b9577a 100644
>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>> @@ -796,6 +796,12 @@ int coresight_get_cpu(struct device *dev)
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>> +int coresight_get_static_trace_id(struct device *dev, u32 *id)
>> +{
>> +    return fwnode_property_read_u32(dev_fwnode(dev), "arm,static- 
>> trace-id", id);
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
>> +
>>   struct coresight_platform_data *
>>   coresight_get_platform_data(struct device *dev)
>>   {
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/ 
>> drivers/hwtracing/coresight/coresight-trace-id.c
>> index d98e12cb30ec..df8fe50b413f 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>> @@ -12,6 +12,12 @@
>>   #include "coresight-trace-id.h"
>> +enum trace_id_flags {
>> +    TRACE_ID_ANY = 0x0,
>> +    TRACE_ID_PREFER_ODD = 0x1,
>> +    TRACE_ID_REQ_STATIC = 0x2,
>> +};
>> +
>>   /* Default trace ID map. Used in sysfs mode and for system sources */
>>   static DEFINE_PER_CPU(atomic_t, id_map_default_cpu_ids) = 
>> ATOMIC_INIT(0);
>>   static struct coresight_trace_id_map id_map_default = {
>> @@ -74,16 +80,18 @@ static int coresight_trace_id_find_odd_id(struct 
>> coresight_trace_id_map *id_map)
>>    * 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, unsigned int flags)
>>   {
>>       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;
>> -    } else if (prefer_odd_id) {
>> +    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 (flags & TRACE_ID_REQ_STATIC)
>> +            return -EINVAL;
> 
> nit: EBUSY sounds like a better choice here ? Requested ID is not
> available.
> 
> Additionally, do we need to handle a case where the preferred_id is
> not valid ? I think we silently allocate a new trace id in such case ?
> 
> Rest looks good to me.
> 
> Suzuki
> 
> 

If preferred_id is not valid, a random id will be allocated for the 
source. For the normal source, 0 is provided here as preferred_id.

> 
> 
>> +    } else if (flags & TRACE_ID_PREFER_ODD) {
>>       /* may use odd ids to avoid preferred legacy cpu IDs */
>>           id = coresight_trace_id_find_odd_id(id_map);
>>           if (id)
>> @@ -153,7 +161,7 @@ static int _coresight_trace_id_get_cpu_id(int cpu, 
>> struct coresight_trace_id_map
>>        */
>>       id = coresight_trace_id_alloc_new_id(id_map,
>>                            CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
>> -                         false);
>> +                         TRACE_ID_ANY);
>>       if (!IS_VALID_CS_TRACE_ID(id))
>>           goto get_cpu_id_out_unlock;
>> @@ -188,14 +196,14 @@ static void _coresight_trace_id_put_cpu_id(int 
>> cpu, struct coresight_trace_id_ma
>>       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, unsigned int traceid_flags)
>>   {
>>       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);
>> +    id = coresight_trace_id_alloc_new_id(id_map, preferred_id, 
>> traceid_flags);
>>       spin_unlock_irqrestore(&id_map->lock, flags);
>>       DUMP_ID(id);
>> @@ -255,10 +263,19 @@ 
>> EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id_map);
>>   int coresight_trace_id_get_system_id(void)
>>   {
>> -    return coresight_trace_id_map_get_system_id(&id_map_default);
>> +    /* prefer odd IDs for system components to avoid legacy CPU IDS */
>> +    return coresight_trace_id_map_get_system_id(&id_map_default, 0,
>> +            TRACE_ID_PREFER_ODD);
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>> +int coresight_trace_id_get_static_system_id(int trace_id)
>> +{
>> +    return coresight_trace_id_map_get_system_id(&id_map_default,
>> +            trace_id, TRACE_ID_REQ_STATIC);
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
>> +
>>   void coresight_trace_id_put_system_id(int id)
>>   {
>>       coresight_trace_id_map_put_system_id(&id_map_default, id);
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/ 
>> drivers/hwtracing/coresight/coresight-trace-id.h
>> index 9aae50a553ca..db68e1ec56b6 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
>> @@ -116,6 +116,15 @@ int coresight_trace_id_read_cpu_id_map(int cpu, 
>> struct coresight_trace_id_map *i
>>    */
>>   int coresight_trace_id_get_system_id(void);
>> +/**
>> + * Allocate a CoreSight static trace ID for a system component.
>> + *
>> + * Used to allocate static IDs for system trace sources such as dummy 
>> source.
>> + *
>> + * return: Trace ID or -EINVAL if allocation is impossible.
>> + */
>> +int coresight_trace_id_get_static_system_id(int id);
>> +
>>   /**
>>    * Release an allocated system trace ID.
>>    *
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index c13342594278..129795873072 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -662,6 +662,7 @@ 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_static_trace_id(struct device *dev, u32 *id);
>>   struct coresight_platform_data *coresight_get_platform_data(struct 
>> device *dev);
>>   struct coresight_connection *
>