linux-kernel - Re: [PATCH 03/13] coresight: tmc-etb/etf: Prepare to handle errors enabling

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Date:   Wed, 15 Aug 2018 13:22:46 -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,
        robert.walker@....com, mike.leach@....com
Subject: Re: [PATCH 03/13] coresight: tmc-etb/etf: Prepare to handle errors
 enabling

On Mon, Aug 06, 2018 at 02:41:45PM +0100, Suzuki K Poulose wrote:
> Prepare to handle errors in enabling the hardware and
> report it back to the core driver.
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-tmc-etf.c | 71 +++++++++++++++----------
>  1 file changed, 44 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index 4156c95..ceb4b30 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -15,7 +15,7 @@
>  static int tmc_set_etf_buffer(struct coresight_device *csdev,
>  			      struct perf_output_handle *handle);
>  
> -static void tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
> +static void __tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
>  {
>  	CS_UNLOCK(drvdata->base);
>  
> @@ -34,6 +34,12 @@ static void tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
>  	CS_LOCK(drvdata->base);
>  }
>  
> +static int tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
> +{
> +	__tmc_etb_enable_hw(drvdata);
> +	return 0;
> +}
> +
>  static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
>  {
>  	char *bufp;
> @@ -76,7 +82,7 @@ static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>  	CS_LOCK(drvdata->base);
>  }
>  
> -static void tmc_etf_enable_hw(struct tmc_drvdata *drvdata)
> +static void __tmc_etf_enable_hw(struct tmc_drvdata *drvdata)
>  {
>  	CS_UNLOCK(drvdata->base);
>  
> @@ -92,6 +98,12 @@ static void tmc_etf_enable_hw(struct tmc_drvdata *drvdata)
>  	CS_LOCK(drvdata->base);
>  }
>  
> +static int tmc_etf_enable_hw(struct tmc_drvdata *drvdata)
> +{
> +	__tmc_etf_enable_hw(drvdata);
> +	return 0;
> +}
> +
>  static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
>  {
>  	CS_UNLOCK(drvdata->base);
> @@ -174,8 +186,12 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
>  		drvdata->buf = buf;
>  	}
>  
> -	drvdata->mode = CS_MODE_SYSFS;
> -	tmc_etb_enable_hw(drvdata);
> +	ret = tmc_etb_enable_hw(drvdata);
> +	if (!ret)
> +		drvdata->mode = CS_MODE_SYSFS;
> +	else
> +		/* Free up the buffer if we failed to enable */
> +		used = false;
>  out:
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
>  
> @@ -194,27 +210,25 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data)
>  	struct perf_output_handle *handle = data;
>  
>  	spin_lock_irqsave(&drvdata->spinlock, flags);
> -	if (drvdata->reading) {
> +	do {
>  		ret = -EINVAL;
> -		goto out;
> -	}
> +		if (drvdata->reading)
> +			break;
> +		/*
> +		 * In Perf mode there can be only one writer per sink.  There
> +		 * is also no need to continue if the ETB/ETF is already
> +		 * operated from sysFS.
> +		 */
> +		if (drvdata->mode != CS_MODE_DISABLED)
> +			break;
>  
> -	/*
> -	 * In Perf mode there can be only one writer per sink.  There
> -	 * is also no need to continue if the ETB/ETR is already operated
> -	 * from sysFS.
> -	 */
> -	if (drvdata->mode != CS_MODE_DISABLED) {
> -		ret = -EINVAL;
> -		goto out;
> -	}
> -
> -	ret = tmc_set_etf_buffer(csdev, handle);
> -	if (!ret) {
> -		drvdata->mode = CS_MODE_PERF;
> -		tmc_etb_enable_hw(drvdata);
> -	}
> -out:
> +		ret = tmc_set_etf_buffer(csdev, handle);
> +		if (ret)
> +			break;
> +		ret  = tmc_etb_enable_hw(drvdata);
> +		if (!ret)
> +			drvdata->mode = CS_MODE_PERF;
> +	} while (0);
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
>  
>  	return ret;
> @@ -271,6 +285,7 @@ static void tmc_disable_etf_sink(struct coresight_device *csdev)
>  static int tmc_enable_etf_link(struct coresight_device *csdev,
>  			       int inport, int outport)
>  {
> +	int ret;
>  	unsigned long flags;
>  	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>  
> @@ -280,11 +295,13 @@ static int tmc_enable_etf_link(struct coresight_device *csdev,
>  		return -EBUSY;
>  	}
>  
> -	tmc_etf_enable_hw(drvdata);
> -	drvdata->mode = CS_MODE_SYSFS;
> +	ret = tmc_etf_enable_hw(drvdata);
> +	if (!ret)
> +		drvdata->mode = CS_MODE_SYSFS;
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
>  
> -	dev_dbg(drvdata->dev, "TMC-ETF enabled\n");
> +	if (!ret)
> +		dev_dbg(drvdata->dev, "TMC-ETF enabled\n");
>  	return 0;

We need to tell the caller if an error as occured:

        return ret;

>  }
>  
> @@ -579,7 +596,7 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
>  		 * can't be NULL.
>  		 */
>  		memset(drvdata->buf, 0, drvdata->size);
> -		tmc_etb_enable_hw(drvdata);
> +		__tmc_etb_enable_hw(drvdata);
>  	} else {
>  		/*
>  		 * The ETB/ETF is not tracing and the buffer was just read.
> -- 
> 2.7.4
>