Re: [PATCH v2 2/9] Coresight: Add coresight TPDM source driver

[Jinlong Mao <quic_jinlmao@quicinc.com>]

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 ?
>
>>> 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