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From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: saiprakash.ranjan@codeaurora.org, mathieu.poirier@linaro.org,
	leo.yan@linaro.org, robh+dt@kernel.org,
	devicetree@vger.kernel.org, alexander.shishkin@linux.intel.com,
	david.brown@linaro.org, mark.rutland@arm.com
Cc: rnayak@codeaurora.org, linux-arm-msm@vger.kernel.org,
	linux-kernel@vger.kernel.org, sibis@codeaurora.org,
	vivek.gautam@codeaurora.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCHv2 2/2] coresight: Abort probe if cpus are not available
Date: Fri, 21 Jun 2019 10:40:02 +0100	[thread overview]
Message-ID: <d6e6a32e-4e15-5bc8-42f9-6cfe72fc0910@arm.com> (raw)
In-Reply-To: <65050e4cb2b0433f3cb9b1ca0bf6ec49d0751086.1561054498.git.saiprakash.ranjan@codeaurora.org>

On 06/20/2019 07:31 PM, Sai Prakash Ranjan wrote:
> Currently coresight etm and cpu-debug will go ahead with
> the probe even when corresponding cpus are not available
> and error out later in the probe path. In such cases, it
> is better to abort the probe earlier.
> 
> Without this, setting *nosmp* will throw below errors:
> 
>   [    5.910622] coresight-cpu-debug 850000.debug: Coresight debug-CPU0 initialized
>   [    5.914266] coresight-cpu-debug 852000.debug: CPU1 debug arch init failed
>   [    5.921474] coresight-cpu-debug 854000.debug: CPU2 debug arch init failed
>   [    5.928328] coresight-cpu-debug 856000.debug: CPU3 debug arch init failed
>   [    5.935330] coresight etm0: CPU0: ETM v4.0 initialized
>   [    5.941875] coresight-etm4x 85d000.etm: ETM arch init failed
>   [    5.946794] coresight-etm4x: probe of 85d000.etm failed with error -22
>   [    5.952707] coresight-etm4x 85e000.etm: ETM arch init failed
>   [    5.958945] coresight-etm4x: probe of 85e000.etm failed with error -22
>   [    5.964853] coresight-etm4x 85f000.etm: ETM arch init failed
>   [    5.971096] coresight-etm4x: probe of 85f000.etm failed with error -22

That is expected. What else do you expect ?

> 
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
>   drivers/hwtracing/coresight/coresight-platform.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 8b03fa573684..3f4559596c6b 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -168,6 +168,9 @@ static int of_coresight_get_cpu(struct device *dev)
>   	cpu = of_cpu_node_to_id(dn);
>   	of_node_put(dn);
>   
> +	if (num_online_cpus() <= cpu)
> +		return -ENODEV;

That is a pointless and terribly wrong check. What if you have only 2
online CPUs (CPU0 and CPU4) and you were processing the ETM for CPU4 ?

More over you should simply let the driver handle a case where the CPU
is not online. May be the driver could register a hotplug notifier and
bring itself up when the CPU comes online.

So, please drop this patch.

Kind regards
Suzuki

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  reply	other threads:[~2019-06-21  9:54 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20 18:31 [PATCHv2 0/2] coresight: Do not default to CPU0 for missing CPU phandle Sai Prakash Ranjan
2019-06-20 18:31 ` [PATCHv2 1/2] " Sai Prakash Ranjan
2019-06-21  9:48   ` Suzuki K Poulose
2019-06-21 10:33     ` Sai Prakash Ranjan
2019-06-20 18:31 ` [PATCHv2 2/2] coresight: Abort probe if cpus are not available Sai Prakash Ranjan
2019-06-21  9:40   ` Suzuki K Poulose [this message]
2019-06-21 10:31     ` Sai Prakash Ranjan

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