linux-kernel - Re: [RFC PATCH 04/14] coresight: etm4x: Free up argument of etm4_init_arch

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Date:   Thu, 30 Jul 2020 11:31:31 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mike.leach@...aro.org, coresight@...ts.linaro.org
Subject: Re: [RFC PATCH 04/14] coresight: etm4x: Free up argument of
 etm4_init_arch_data

On Wed, Jul 22, 2020 at 06:20:30PM +0100, Suzuki K Poulose wrote:
> etm4_init_arch_data is called early during the device probe,
> even before the coresight_device is registered. Since we are
> about to replace the direct access via abstraction layer, we
> need a way to pass in the csdev_access for the given device.
> Towards this free up the argument, which is already available
> via etmdrvdata[smp_processor_id()].
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 7bb74c659c4f..67deb4a4e618 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -614,7 +614,8 @@ static const struct coresight_ops etm4_cs_ops = {
>  	.source_ops	= &etm4_source_ops,
>  };
>  
> -static void etm4_init_arch_data(void *info)
> +
> +static void etm4_init_arch_data(void *__unused)
>  {
>  	u32 etmidr0;
>  	u32 etmidr1;
> @@ -622,8 +623,14 @@ static void etm4_init_arch_data(void *info)
>  	u32 etmidr3;
>  	u32 etmidr4;
>  	u32 etmidr5;
> -	struct etmv4_drvdata *drvdata = info;
> -	int i;
> +	struct etmv4_drvdata *drvdata;
> +	int i, cpu;
> +
> +	cpu = raw_smp_processor_id();

Can you provide details on the motivation to use the raw_ version over the regular
one?  As far as I can see in linux/smp.h there is no difference between them
unless DEBUB_PREEMPT is enabled.  Even then the debug version won't complain
since the task is CPU affined.

> +	drvdata = etmdrvdata[cpu];
> +
> +	if (WARN_ON(!etmdrvdata[cpu]))
> +		return;
>  
>  	/* Make sure all registers are accessible */
>  	etm4_os_unlock(drvdata);
> @@ -1517,7 +1524,7 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>  	etmdrvdata[drvdata->cpu] = drvdata;
>  
>  	if (smp_call_function_single(drvdata->cpu,
> -				etm4_init_arch_data,  drvdata, 1))
> +				etm4_init_arch_data,  NULL, 1))
>  		dev_err(dev, "ETM arch init failed\n");
>  
>  	ret = etm4_pm_setup_cpuslocked();
> -- 
> 2.24.1
>