Message-ID: <25d9a681-b899-5936-868d-34f645ee40ef@quicinc.com>
Date:   Thu, 27 Jan 2022 17:33:26 +0800
From:   Jinlong Mao <quic_jinlmao@...cinc.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     Mike Leach <mike.leach@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        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>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang <quic_taozha@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 2/9] Coresight: Add coresight TPDM source driver


On 1/26/2022 11:34 PM, Mathieu Poirier wrote:
> On Wed, Jan 26, 2022 at 03:07:38PM +0800, Jinlong Mao wrote:
>> Hi Mathieu,
>>
>> Good afternoon.
>>
>> On 1/22/2022 1:15 AM, Mathieu Poirier wrote:
>>> Hey Jinlong,
>>>
>>> On Fri, Jan 21, 2022 at 10:01:47PM +0800, Jinlong Mao wrote:
>>>> Hi Mathieu,
>>>>
>>>> Good Day.
>>>>
>>>> On 12/17/2021 3:02 AM, Mathieu Poirier wrote:
>>>>> [...]
>>>>>
>>>>>>>>> +
>>>>>>>>> +static void tpdm_init_default_data(struct tpdm_drvdata *drvdata)
>>>>>>>>> +{
>>>>>>>>> +    static int traceid = TPDM_TRACE_ID_START;
>>>>>>>>> +
>>>>>>>>> +    drvdata->traceid = traceid++;
>>>>>>>>> +}
>>>>>>>> I have been specific on how to properly do this in the last revision.  Given the
>>>>>>>> above about the MAINTAINERS file, I am not sure that I will continue reviewing this set.
>>>>>>>>
>>>>>>>> There is also no need to rush another revision as I won't have the bandwidth to
>>>>>>>> process it before the holidays.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Mathieu
>>>>>>> Hi Mathieu,
>>>>>>>
>>>>>>> Sorry, not addressed your previous comments here.
>>>>>>>
>>>>>>> For the trace id, each coresight component has 7 bits to store the trace
>>>>>>> id. So the trace id should be from 1 to 127 as 0 is invalid.
>>>>>> IDs 0x70 - 0x7F (`112 - 127 ) are reserved - see the ARM Coresight
>>>>>> Architecture specification v3.0
>>>>>>
>>>>> Correct
>>>>>
>>>>>>> Apart from TPDMs/STM/ETMs, we also have other coresight components in
>>>>>>> our internal device. About 80 ids are already used.
>>>>>>>
>>>>>>> Some components have fixed trace id in HW. If we use functions below to
>>>>>>> count the trace id, there will be conflict to other components.
>>>>>>>
>>>>>>> Can we use 1-15 for etm trace ids  and 16 - 127 for other coresight
>>>>>>> components ? And handle trace ids in its' own driver ?
>>>>>>>
>>>>>> This will limit systems to 15 cores - some have more!
>>>>>>
>>>>> Correct
>>>>>
>>>>>>> static inline int coresight_get_system_trace_id(int id)
>>>>>>> {
>>>>>>>             /* Start system IDs above the highest per CPU trace ID. */
>>>>>>>             return coresigth_get_trace_id(cpumask_last(cpu_possible_mask) + 1);
>>>>>>> }
>>>>> Looking at my own suggestion again this won't work since it returns the same traceID
>>>>> when called multiple times.
>>>>>
>>>>> For this patchset and _without_ taking into account internal devices that have
>>>>> their traceID set in HW:
>>>>>
>>>>> 1. Define a bitmask that is 7 bit wide.
>>>> Should it be a 128 bit wide bitmask  (0--127)?
>>> Yes, you are correct.
>>>
>>>>> 2. By default, set bits under 0x10 and between 0x70 - 0x7F.
>>>>> 3. In coresight_get_system_trace_id(), drop the @id parameter and allocate the
>>>>> first available bit after cpumask_last(cpu_possible_mask) + 1.
>>>> Should it allocate the first available bit after (cpumask_last(cpu_possible_mask) *2 ) + 0x10 ?
>>>> Return the first zero bit position as the trace id and set the bit.
>>> I need to clarify something with Mike on this - I will get back to you on
>>> Monday.
>> Do you have more comments on this ?
> I just received clarifications on this - there is no need to continue enacting
> the current scheme and as such reserving bits following the above formula will
> not be needed either.  Simply assigning free traceIDs based on request will
> work just fine.
>
> That of course is taking into account that 0x0, 0x1 and 0x70 - 0x7f are
> reserved.  0x1 is currently used for STM and should eventually be fixed to
> simply request a traceID the same way any other component do.  You can fix it as
> part of this set but it is not mandatory.
>
> Let me know if there are things I haven't been clear on.
>
> Thanks,
> Mathieu

Hi Mathieu,


Do you mean ETM sources and other sources can share the same 
"coresight_get_trace_id" function ?


int trace_id = 1;

int coresight_get_trace_id ()
{
     trace_id += 1;
     if (trace_id > 1 && trace_id < 0x70)
         return trace_id;
     else
         return -EINVAL;
}

or do we still need a different function for other sources like use 
"coresight_get_system_trace_id" ?
Return the id from 1 and skip the ids which equeals to 
CORESIGHT_ETM_PMU_SEED + (cpu * 2).

Thanks

Jinlong Mao

>>>>> 4. Define a new function called coresight_put_system_trace_id(int id) that
>>>>> clears the bit in the mask corresponding to @id.
>>>>>
>>>>> For now that should work.
>>>>>
>>>>>>> static inline int coresight_get_trace_id(int cpu)
>>>>>>> {
>>>>>>>         /*
>>>>>>>          * A trace ID of value 0 is invalid, so let's start at some
>>>>>>>          * random value that fits in 7 bits and go from there.  Since
>>>>>>>          * the common convention is to have data trace IDs be I(N) + 1,
>>>>>>>          * set instruction trace IDs as a function of the CPU number.
>>>>>>>          */
>>>>>>>         return (CORESIGHT_ETM_PMU_SEED + (cpu * 2));
>>>>>>> }
>>>>>>>
>>>>>> This fixed relationship between cpu and trace ID is used in the perf
>>>>>> tooling to populate the elements in the perf.data file to correctly
>>>>>> allow association between CPU and trace data, and thus allow correct
>>>>>> trace decode.
>>>>> TraceIDs associated to CPUs are communicated to the perf tooling by way of the
>>>>> perf header - theoretically we should be able to change the allocation scheme
>>>>> without impacting the decoding process.
>>>>>
>>>>>> It should be possible to create another more dynamic mapping scheme -
>>>>>> but this must include a way to support the perf requirements too.
>>>>>>
>>>>> TraceIDs have been a lurking problem for as long as the subsystem has existed.
>>>>> For now what I have suggested above should be sufficient to provide an
>>>>> in-between solution that doesn't hold back this patchset.
>>>>>
>>>>> That being said, we need to start thinking about the best way to do this.  I
>>>>> will put a patchset together in the new year that aims in that direction.
>>>>>
>>>>>> Regards
>>>>>>
>>>>>> Mike
>>>>>>
>>>>>>> Thanks
>>>>>>>
>>>>>>> Jinlong Mao
>>>>>>>
>>>>>>>>> +
>>>>>>>>> +static int tpdm_probe(struct amba_device *adev, const struct amba_id *id)
>>>>>>>>> +{
>>>>>>>>> +    struct device *dev = &adev->dev;
>>>>>>>>> +    struct coresight_platform_data *pdata;
>>>>>>>>> +    struct tpdm_drvdata *drvdata;
>>>>>>>>> +    struct coresight_desc desc = { 0 };
>>>>>>>>> +
>>>>>>>>> +    desc.name = coresight_alloc_device_name(&tpdm_devs, dev);
>>>>>>>>> +    if (!desc.name)
>>>>>>>>> +            return -ENOMEM;
>>>>>>>>> +    pdata = coresight_get_platform_data(dev);
>>>>>>>>> +    if (IS_ERR(pdata))
>>>>>>>>> +            return PTR_ERR(pdata);
>>>>>>>>> +    adev->dev.platform_data = pdata;
>>>>>>>>> +
>>>>>>>>> +    drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
>>>>>>>>> +    if (!drvdata)
>>>>>>>>> +            return -ENOMEM;
>>>>>>>>> +    drvdata->dev = &adev->dev;
>>>>>>>>> +    dev_set_drvdata(dev, drvdata);
>>>>>>>>> +
>>>>>>>>> +    drvdata->base = devm_ioremap_resource(dev, &adev->res);
>>>>>>>>> +    if (!drvdata->base)
>>>>>>>>> +            return -ENOMEM;
>>>>>>>>> +
>>>>>>>>> +    mutex_init(&drvdata->lock);
>>>>>>>>> +
>>>>>>>>> +    desc.type = CORESIGHT_DEV_TYPE_SOURCE;
>>>>>>>>> +    desc.subtype.source_subtype = CORESIGHT_DEV_SUBTYPE_SOURCE_SYS;
>>>>>>>>> +    desc.ops = &tpdm_cs_ops;
>>>>>>>>> +    desc.pdata = adev->dev.platform_data;
>>>>>>>>> +    desc.dev = &adev->dev;
>>>>>>>>> +    drvdata->csdev = coresight_register(&desc);
>>>>>>>>> +    if (IS_ERR(drvdata->csdev))
>>>>>>>>> +            return PTR_ERR(drvdata->csdev);
>>>>>>>>> +
>>>>>>>>> +    tpdm_init_default_data(drvdata);
>>>>>>>>> +    pm_runtime_put(&adev->dev);
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void __exit tpdm_remove(struct amba_device *adev)
>>>>>>>>> +{
>>>>>>>>> +    struct tpdm_drvdata *drvdata = dev_get_drvdata(&adev->dev);
>>>>>>>>> +
>>>>>>>>> +    coresight_unregister(drvdata->csdev);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static struct amba_id tpdm_ids[] = {
>>>>>>>>> +    {
>>>>>>>>> +            .id = 0x000f0e00,
>>>>>>>>> +            .mask = 0x000fff00,
>>>>>>>>> +    },
>>>>>>>>> +    { 0, 0},
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static struct amba_driver tpdm_driver = {
>>>>>>>>> +    .drv = {
>>>>>>>>> +            .name   = "coresight-tpdm",
>>>>>>>>> +            .owner  = THIS_MODULE,
>>>>>>>>> +            .suppress_bind_attrs = true,
>>>>>>>>> +    },
>>>>>>>>> +    .probe          = tpdm_probe,
>>>>>>>>> +    .id_table       = tpdm_ids,
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +module_amba_driver(tpdm_driver);
>>>>>>>>> +
>>>>>>>>> +MODULE_LICENSE("GPL v2");
>>>>>>>>> +MODULE_DESCRIPTION("Trace, Profiling & Diagnostic Monitor driver");
>>>>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/drivers/hwtracing/coresight/coresight-tpdm.h
>>>>>>>>> new file mode 100644
>>>>>>>>> index 000000000000..980ae90ff1c8
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/drivers/hwtracing/coresight/coresight-tpdm.h
>>>>>>>>> @@ -0,0 +1,31 @@
>>>>>>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>>>>>>> +/*
>>>>>>>>> + * Copyright (c) 2021 Qualcomm Innovation Center, Inc. All rights reserved.
>>>>>>>>> + */
>>>>>>>>> +
>>>>>>>>> +#ifndef _CORESIGHT_CORESIGHT_TPDM_H
>>>>>>>>> +#define _CORESIGHT_CORESIGHT_TPDM_H
>>>>>>>>> +
>>>>>>>>> +/* Default value of the traceid */
>>>>>>>>> +#define TPDM_TRACE_ID_START 128
>>>>>>>>> +
>>>>>>>>> +/**
>>>>>>>>> + * struct tpdm_drvdata - specifics associated to an TPDM component
>>>>>>>>> + * @base:       memory mapped base address for this component.
>>>>>>>>> + * @dev:        The device entity associated to this component.
>>>>>>>>> + * @csdev:      component vitals needed by the framework.
>>>>>>>>> + * @lock:       lock for the enable value.
>>>>>>>>> + * @enable:     enable status of the component.
>>>>>>>>> + * @traceid:    value of the current ID for this component.
>>>>>>>>> + */
>>>>>>>>> +
>>>>>>>>> +struct tpdm_drvdata {
>>>>>>>>> +    void __iomem            *base;
>>>>>>>>> +    struct device           *dev;
>>>>>>>>> +    struct coresight_device *csdev;
>>>>>>>>> +    struct mutex            lock;
>>>>>>>>> +    bool                    enable;
>>>>>>>>> +    int                     traceid;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +#endif  /* _CORESIGHT_CORESIGHT_TPDM_H */
>>>>>>>>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>>>>>>>>> index 93a2922b7653..e48d463be63b 100644
>>>>>>>>> --- a/include/linux/coresight.h
>>>>>>>>> +++ b/include/linux/coresight.h
>>>>>>>>> @@ -65,6 +65,7 @@ enum coresight_dev_subtype_source {
>>>>>>>>>         CORESIGHT_DEV_SUBTYPE_SOURCE_PROC,
>>>>>>>>>         CORESIGHT_DEV_SUBTYPE_SOURCE_BUS,
>>>>>>>>>         CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE,
>>>>>>>>> +    CORESIGHT_DEV_SUBTYPE_SOURCE_SYS,
>>>>>>>>>      };
>>>>>>>>>
>>>>>>>>>      enum coresight_dev_subtype_helper {
>>>>>>>>> --
>>>>>>>>> 2.17.1
>>>>>>>>>
>>>>>> -- 
>>>>>> Mike Leach
>>>>>> Principal Engineer, ARM Ltd.
>>>>>> Manchester Design Centre. UK

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