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

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Date:   Mon, 4 Dec 2023 10:54:15 +0000
From:   James Clark <james.clark@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com
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 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.
> 
[...]
> -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);
> +	if (ret) {
> +		pm_runtime_put_noidle(&pdev->dev);
> +		pm_runtime_disable(&pdev->dev);
> +	}

I'm not sure if these pm_runtime()s are right because there is already a
put inside of __tmc_probe() if it fails. If you unload and then reload
all the coresight modules with these patches you get these errors which
are new:

  coresight-tpiu-platform ARMHC979:00: Unbalanced pm_runtime_enable!
  CSCFG registered etm0
  coresight etm0: CPU0: etm v4.2 initialized
  CSCFG registered etm1
  coresight etm1: CPU1: etm v4.2 initialized
  CSCFG registered etm2
  coresight etm2: CPU2: etm v4.2 initialized
  CSCFG registered etm3
  coresight etm3: CPU3: etm v4.2 initialized
  coresight-tmc-platform ARMHC97C:00: Unbalanced pm_runtime_enable!
  coresight-tmc-platform ARMHC97C:01: Unbalanced pm_runtime_enable!
  coresight-tmc-platform ARMHC97C:02: Unbalanced pm_runtime_enable!
  coresight-tmc-platform ARMHC97C:03: Unbalanced pm_runtime_enable!

It might be worth testing all of these pm_runtime()s, including the
error case ones, because loading and unloading the modules doesn't even
include the error scenarios, so there are probably more bad ones in
there too.