linux-kernel - Re: [RFC PATCH 01/20] coresight: etm3x: splitting 'etm_enable

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Date:	Wed, 30 Sep 2015 12:58:11 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	gregkh@...uxfoundation.org, a.p.zijlstra@...llo.nl,
	acme@...nel.org, mingo@...hat.com, corbet@....net
Cc:	adrian.hunter@...el.com, zhang.chunyan@...aro.org,
	mike.leach@....com, tor@...com, al.grant@....com,
	pawel.moll@....com, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 01/20] coresight: etm3x: splitting 'etm_enable_hw()' operations

Mathieu Poirier <mathieu.poirier@...aro.org> writes:

> -static void etm_enable_hw(void *info)
> +static void etm_power_up_cpu(void *info)
>  {
> -	int i;
> -	u32 etmcr;
> -	struct etm_drvdata *drvdata = info;
> +	struct coresight_device *csdev = info;
> +	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> +	WARN_ON(drvdata->cpu != smp_processor_id());

Maybe WARN_ON_ONCE() is sufficient here (and other similar places).

> +static void etm_power_down_cpu(void *info)
> +{
> +	struct coresight_device *csdev = info;
> +	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> +	WARN_ON(drvdata->cpu != smp_processor_id());

Likewise.

> +/**
> + * etm_configure_cpu - configure ETM registers
> + * @csdev - the etm that needs to be configure.
> + *
> + * Applies a configuration set to the ETM registers _without_ enabling the
> + * tracer.  This function needs to be executed on the CPU who's tracer is
> + * being configured.
> + */
> +static void etm_configure_cpu(void *info)
> +{
> +	int i;
> +	u32 etmcr;
> +	struct coresight_device *csdev = info;
> +	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> +	WARN_ON(drvdata->cpu != smp_processor_id());

Likewise.

> +
> +	CS_UNLOCK(drvdata->base);
>  	etm_set_prog(drvdata);
>  
>  	etmcr = etm_readl(drvdata, ETMCR);
> -	etmcr &= (ETMCR_PWD_DWN | ETMCR_ETM_PRG);
>  	etmcr |= drvdata->port_size;
>  	etm_writel(drvdata, drvdata->ctrl | etmcr, ETMCR);
>  	etm_writel(drvdata, drvdata->trigger_event, ETMTRIGGER);

Most of these things can also be bypassed, as at least initially perf
events won't be using trigger/sequencer configurations, so we could
simply clear all these things out when a first perf event is created
(which would also disallow any sysfs poking around the etm/etb) and not
worry about them in the pmu callbacks.

Regards,
--
Alex
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