linux-kernel - Re: [PATCH v2 3/4] coresight: etm3x: Deal with CLAIM tag before and after accessing HW

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Date:   Thu, 8 Nov 2018 17:13:46 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-arm-kernel@...ts.infradead.org
Cc:     alexander.shishkin@...ux.intel.com, leo.yan@...aro.org,
        coresight@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] coresight: etm3x: Deal with CLAIM tag before and
 after accessing HW

Hi,

On 07/11/2018 23:08, Mathieu Poirier wrote:
> This patch moves access to the CLAIM tag so that no modification to the HW
> happens before and after the CLAIM operation has been carried.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>   drivers/hwtracing/coresight/coresight-etm3x.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> index fd5c4cca7db5..4f638d81a66a 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -363,15 +363,16 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>   
>   	CS_UNLOCK(drvdata->base);
>   
> +	rc = coresight_claim_device_unlocked(drvdata->base);
> +	if (rc)
> +		goto done;
> +
>   	/* Turn engine on */
>   	etm_clr_pwrdwn(drvdata);
>   	/* Apply power to trace registers */
>   	etm_set_pwrup(drvdata);
>   	/* Make sure all registers are accessible */
>   	etm_os_unlock(drvdata);
> -	rc = coresight_claim_device_unlocked(drvdata->base);
> -	if (rc)
> -		goto done;
>   
>   	etm_set_prog(drvdata);
>   
> @@ -422,12 +423,11 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>   	etm_clr_prog(drvdata);
>   
>   done:
> -	if (rc)
> -		etm_set_pwrdwn(drvdata);
>   	CS_LOCK(drvdata->base);
>   
> -	dev_dbg(drvdata->dev, "cpu: %d enable smp call done: %d\n",
> -		drvdata->cpu, rc);
> +	if (!rc)
> +		dev_dbg(drvdata->dev, "cpu: %d enable smp call done: %d\n",
> +			drvdata->cpu, rc);

Isn't it good to report the failure case too ? Anyway it is dev_dbg and
will be a useful info when we debug issues. Otherwise,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>

>   	return rc;
>   }
>   
> @@ -577,9 +577,9 @@ static void etm_disable_hw(void *info)
>   	for (i = 0; i < drvdata->nr_cntr; i++)
>   		config->cntr_val[i] = etm_readl(drvdata, ETMCNTVRn(i));
>   
> +	etm_set_pwrdwn(drvdata);
>   	coresight_disclaim_device_unlocked(drvdata->base);
>   
> -	etm_set_pwrdwn(drvdata);
>   	CS_LOCK(drvdata->base);
>   
>   	dev_dbg(drvdata->dev, "cpu: %d disable smp call done\n", drvdata->cpu);
>