linux-kernel - Re: [PATCH v1 2/3] coresight: Add reserve trace id support

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Message-ID: <7d5c21af-3488-4c8e-aa64-ba15ee3c581c@quicinc.com>
Date: Mon, 20 May 2024 14:03:11 +0800
From: Jinlong Mao <quic_jinlmao@...cinc.com>
To: James Clark <james.clark@....com>
CC: <coresight@...ts.linaro.org>, <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang
	<quic_taozha@...cinc.com>,
        songchai <quic_songchai@...cinc.com>,
        "Suzuki K
 Poulose" <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>, "Rob
 Herring" <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        "Conor
 Dooley" <conor+dt@...nel.org>,
        Alexander Shishkin
	<alexander.shishkin@...ux.intel.com>
Subject: Re: [PATCH v1 2/3] coresight: Add reserve trace id support

Hi James,

On 2024/5/16 21:23, James Clark wrote:
> 
> 
> On 16/05/2024 04:56, 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. Reserve trace id
>> for this kind of hardware source.
>>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
>> ---
>>   .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++++++++
>>   .../hwtracing/coresight/coresight-trace-id.c  | 24 +++++++++++++++++
>>   .../hwtracing/coresight/coresight-trace-id.h  | 11 ++++++++
>>   include/linux/coresight.h                     |  1 +
>>   4 files changed, 62 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
>> index 9d550f5697fa..d3e22a2608df 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
>> @@ -315,6 +326,12 @@ static inline int of_coresight_get_cpu(struct device *dev)
>>   {
>>   	return -ENODEV;
>>   }
>> +
>> +static int of_coresight_get_trace_id(struct device *dev, u32 *id)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>>   #endif
>>   
>>   #ifdef CONFIG_ACPI
>> @@ -794,6 +811,15 @@ int coresight_get_cpu(struct device *dev)
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>>   
>> +int coresight_get_trace_id(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_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 af5b4ef59cea..536a34e9de6f 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>> @@ -110,6 +110,24 @@ static int coresight_trace_id_alloc_new_id(struct coresight_trace_id_map *id_map
>>   	return id;
>>   }
>>   
>> +static int coresight_trace_id_set(int id, struct coresight_trace_id_map *id_map)
>> +{
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&id_map_lock, flags);
>> +
>> +	if (WARN(!IS_VALID_CS_TRACE_ID(id), "Invalid Trace ID %d\n", id))
>> +		return -EINVAL;
>> +	if (WARN(test_bit(id, id_map->used_ids), "ID is already used: %d\n", id))
>> +		return -EINVAL;
> 
> Do these returns not skip unlocking the spinlock?

Yes. Missing the unlocking the spinlock here.

> 
> It might be slightly fewer changes if we update the existing
> coresight_trace_id_alloc_new_id() to add a new "only_preferred" option.
> 
> Then use the existing system id allocator which already handles the lock
> and unlock properly:
> 
>    static int coresight_trace_id_map_get_system_id(struct
>                               coresight_trace_id_map *id_map, int id,
> 
>                               bool only_preferred)
>    {
>    ...
> 	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, id, true,
>                                               only_preferred);
>          spin_unlock_irqrestore(&id_map_lock, flags);
>    ...
> 
> I suppose the end result is the same as your implementation, but it
> trades making one existing function slightly more complicated instead of
> adding some new ones.
yes. Your suggestion looks better. I will think carefully.