linux-kernel - Re: [PATCH] coresight: add PM runtime calls to coresight_simple

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Message-ID: <576C1038.502@arm.com>
Date:	Thu, 23 Jun 2016 17:37:12 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: add PM runtime calls to
 coresight_simple_func()



On 17/06/16 18:41, Mathieu Poirier wrote:
> It is mandatory to enable a coresight block's power domain before
> trying to access management registers.  Otherwise the transaction
> simply stalls, leading to a system hang.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>   drivers/hwtracing/coresight/coresight-priv.h | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index ad975c58080d..b047241e7496 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -16,6 +16,7 @@
>   #include <linux/bitops.h>
>   #include <linux/io.h>
>   #include <linux/coresight.h>
> +#include <linux/pm_runtime.h>
>
>   /*
>    * Coresight management registers (0xf00-0xfcc)
> @@ -42,8 +43,10 @@ static ssize_t name##_show(struct device *_dev,				\
>   			   struct device_attribute *attr, char *buf)	\
>   {									\
>   	type *drvdata = dev_get_drvdata(_dev->parent);			\
> +	pm_runtime_get_sync(_dev->parent);				\
>   	return scnprintf(buf, PAGE_SIZE, "0x%x\n",			\
>   			 readl_relaxed(drvdata->base + offset));	\
> +	pm_runtime_put_sync(_dev->parent);				\

This is wrong, I just noticed when I was playing around this.
Perhaps you meant to do this before returning ? I wonder why compiler
doesn't throw any error.

-- 
Regards,
Sudeep