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

[Suzuki K Poulose]

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@xxxxxxxxxx>
> > Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> > Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > Cc: James Clark <james.clark@xxxxxxx>
> > Cc: linux-acpi@xxxxxxxxxxxxxxx
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Cc: coresight@xxxxxxxxxxxxxxxx
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > ---
> >   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