linux-kernel - Re: [PATCH 1/2] coresight: Set affinity to invalid for missing CPU phandle

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Date:   Thu, 20 Jun 2019 11:39:08 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/2] coresight: Set affinity to invalid for missing CPU
 phandle

Hi Sai,

On Thu, Jun 20, 2019 at 07:15:46PM +0530, Sai Prakash Ranjan wrote:
> Affinity defaults to CPU0 in case of missing CPU phandle
> and this leads to crashes in some cases because of such
> wrong assumption. Fix this by returning -ENODEV in
> coresight platform for such cases and then handle it
> in the coresight drivers.
> 
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> ---
>  drivers/hwtracing/coresight/coresight-platform.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 3c5ceda8db24..b1ea60c210e1 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -160,15 +160,17 @@ static int of_coresight_get_cpu(struct device *dev)
>  
>  	if (!dev->of_node)
>  		return 0;

An error should be returned if the above condition is true.  

> +

Spurious newline

>  	dn = of_parse_phandle(dev->of_node, "cpu", 0);
> -	/* Affinity defaults to CPU0 */
> +
> +	/* Affinity defaults to invalid if no cpu nodes are found*/
>  	if (!dn)
> -		return 0;
> +		return -ENODEV;
> +
>  	cpu = of_cpu_node_to_id(dn);
>  	of_node_put(dn);
>  
> -	/* Affinity to CPU0 if no cpu nodes are found */
> -	return (cpu < 0) ? 0 : cpu;
> +	return cpu;
>  }
>  
>  /*
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>