linux-kernel - Re: [PATCH V2 5/7] coresight: tmc: Move ACPI support from AMBA driver to platform driver

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Message-ID: <d24b5a25-1a1b-4de5-95ff-c49ca8f8101c@arm.com>
Date:   Mon, 4 Dec 2023 10:50:42 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     James Clark <james.clark@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V2 5/7] coresight: tmc: Move ACPI support from AMBA driver
 to platform driver

On 04/12/2023 10:42, James Clark wrote:
> 
> 
> On 01/12/2023 06:20, Anshuman Khandual wrote:
>> Add support for the tmc devices in the platform driver, which can then be
>> used on ACPI based platforms. This change would now allow runtime power
>> management for ACPI based systems. The driver would try to enable the APB
>> clock if available.
>>
>> Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>
>> Cc: Sudeep Holla <sudeep.holla@....com>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: Mike Leach <mike.leach@...aro.org>
>> Cc: James Clark <james.clark@....com>
>> Cc: linux-acpi@...r.kernel.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Cc: coresight@...ts.linaro.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>   drivers/acpi/arm64/amba.c                     |   2 -
>>   .../hwtracing/coresight/coresight-tmc-core.c  | 130 +++++++++++++++---
>>   drivers/hwtracing/coresight/coresight-tmc.h   |   1 +
>>   3 files changed, 115 insertions(+), 18 deletions(-)
>>
> [...]
>> -static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>> +static int __tmc_probe(struct device *dev, struct resource *res, void *dev_caps)
>>   {
>>   	int ret = 0;
>>   	u32 devid;
>>   	void __iomem *base;
>> -	struct device *dev = &adev->dev;
>>   	struct coresight_platform_data *pdata = NULL;
>> -	struct tmc_drvdata *drvdata;
>> -	struct resource *res = &adev->res;
>> +	struct tmc_drvdata *drvdata = dev_get_drvdata(dev);
>>   	struct coresight_desc desc = { 0 };
>>   	struct coresight_dev_list *dev_list = NULL;
>>   
>>   	ret = -ENOMEM;
>> -	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
>> -	if (!drvdata)
>> -		goto out;
>> -
>> -	dev_set_drvdata(dev, drvdata);
>>   
>>   	/* Validity for the resource is already checked by the AMBA core */
>>   	base = devm_ioremap_resource(dev, res);
>> @@ -487,8 +482,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>>   		desc.type = CORESIGHT_DEV_TYPE_SINK;
>>   		desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM;
>>   		desc.ops = &tmc_etr_cs_ops;
>> -		ret = tmc_etr_setup_caps(dev, devid,
>> -					 coresight_get_uci_data(id));
>> +		ret = tmc_etr_setup_caps(dev, devid, dev_caps);
>>   		if (ret)
>>   			goto out;
> [...]
>> -module_amba_driver(tmc_driver);
>> +static int tmc_platform_probe(struct platform_device *pdev)
>> +{
>> +	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	struct tmc_drvdata *drvdata;
>> +	int ret = 0;
>> +
>> +	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
>> +	if (!drvdata)
>> +		return -ENOMEM;
>> +
>> +	drvdata->pclk = coresight_get_enable_apb_pclk(&pdev->dev);
>> +	if (IS_ERR(drvdata->pclk))
>> +		return -ENODEV;
>> +
>> +	dev_set_drvdata(&pdev->dev, drvdata);
>> +	pm_runtime_get_noresume(&pdev->dev);
>> +	pm_runtime_set_active(&pdev->dev);
>> +	pm_runtime_enable(&pdev->dev);
>> +
>> +	ret = __tmc_probe(&pdev->dev, res, NULL);
> 
> What effect does passing NULL here have? It seems like the dev_caps did
> something useful when it's set to CORESIGHT_SOC_600_ETR_CAPS. Maybe
> Suzuki knows as he added it?

That was supposed to initialise the capabilities of the TMC-ETR, which
are not discoverable by ID registers. (e.g., SAVE restore of RRP/RWP).
I guess, we could get rid of that cap and use the "PID" register match
to figure out the capabilities.

Suzuki