linux-kernel - Re: [PATCH v2 03/13] coresight: stm: Update STM driver to use Trace ID API

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Message-ID: <5875dacd-1431-210f-485d-0d47a3d3066f@arm.com>
Date:   Tue, 19 Jul 2022 18:51:34 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mike Leach <mike.leach@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, linux-perf-users@...r.kernel.org,
        leo.yan@...aro.org, quic_jinlmao@...cinc.com
Subject: Re: [PATCH v2 03/13] coresight: stm: Update STM driver to use Trace
 ID API

On 04/07/2022 09:11, Mike Leach wrote:
> Updates the STM driver to use the trace ID allocation API.
> This uses the _system_id calls to allocate an ID on device poll,
> and release on device remove.
> 
> The sysfs access to the STMTRACEIDR register has been changed from RW
> to RO. Having this value as writable is not appropriate for the new
> Trace ID scheme - and had potential to cause errors in the previous
> scheme if values clashed with other sources.
> 
> Signed-off-by: Mike Leach <mike.leach@...aro.org>



> ---
>   drivers/hwtracing/coresight/coresight-stm.c | 41 +++++++--------------
>   1 file changed, 14 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c
> index bb14a3a8a921..9ef3e923a930 100644
> --- a/drivers/hwtracing/coresight/coresight-stm.c
> +++ b/drivers/hwtracing/coresight/coresight-stm.c
> @@ -31,6 +31,7 @@
>   #include <linux/stm.h>
>   
>   #include "coresight-priv.h"
> +#include "coresight-trace-id.h"
>   
>   #define STMDMASTARTR			0xc04
>   #define STMDMASTOPR			0xc08
> @@ -615,24 +616,7 @@ static ssize_t traceid_show(struct device *dev,
>   	val = drvdata->traceid;
>   	return sprintf(buf, "%#lx\n", val);
>   }
> -
> -static ssize_t traceid_store(struct device *dev,
> -			     struct device_attribute *attr,
> -			     const char *buf, size_t size)
> -{
> -	int ret;
> -	unsigned long val;
> -	struct stm_drvdata *drvdata = dev_get_drvdata(dev->parent);
> -
> -	ret = kstrtoul(buf, 16, &val);
> -	if (ret)
> -		return ret;
> -
> -	/* traceid field is 7bit wide on STM32 */
> -	drvdata->traceid = val & 0x7f;
> -	return size;
> -}
> -static DEVICE_ATTR_RW(traceid);
> +static DEVICE_ATTR_RO(traceid);
>   
>   #define coresight_stm_reg(name, offset)	\
>   	coresight_simple_reg32(struct stm_drvdata, name, offset)
> @@ -819,14 +803,6 @@ static void stm_init_default_data(struct stm_drvdata *drvdata)
>   	 */
>   	drvdata->stmsper = ~0x0;
>   
> -	/*
> -	 * The trace ID value for *ETM* tracers start at CPU_ID * 2 + 0x10 and
> -	 * anything equal to or higher than 0x70 is reserved.  Since 0x00 is
> -	 * also reserved the STM trace ID needs to be higher than 0x00 and
> -	 * lowner than 0x10.
> -	 */
> -	drvdata->traceid = 0x1;
> -
>   	/* Set invariant transaction timing on all channels */
>   	bitmap_clear(drvdata->chs.guaranteed, 0, drvdata->numsp);
>   }
> @@ -854,7 +830,7 @@ static void stm_init_generic_data(struct stm_drvdata *drvdata,
>   
>   static int stm_probe(struct amba_device *adev, const struct amba_id *id)
>   {
> -	int ret;
> +	int ret, trace_id;
>   	void __iomem *base;
>   	struct device *dev = &adev->dev;
>   	struct coresight_platform_data *pdata = NULL;
> @@ -938,12 +914,22 @@ static int stm_probe(struct amba_device *adev, const struct amba_id *id)
>   		goto stm_unregister;
>   	}
>   
> +	trace_id = coresight_trace_id_get_system_id();
> +	if (trace_id < 0) {
> +		ret = trace_id;
> +		goto cs_unregister;
> +	}
> +	drvdata->traceid = (u8)trace_id;
> +
>   	pm_runtime_put(&adev->dev);
>   
>   	dev_info(&drvdata->csdev->dev, "%s initialized\n",
>   		 (char *)coresight_get_uci_data(id));
>   	return 0;
>   
> +cs_unregister:
> +	coresight_unregister(drvdata->csdev);
> +
>   stm_unregister:
>   	stm_unregister_device(&drvdata->stm);
>   	return ret;
> @@ -953,6 +939,7 @@ static void stm_remove(struct amba_device *adev)
>   {
>   	struct stm_drvdata *drvdata = dev_get_drvdata(&adev->dev);
>   
> +	coresight_trace_id_put_system_id(drvdata->traceid);

This makes think that, we should add a WARN_ON() in

	coresight_trace_id_put_system_id(id)
	{

		WARN_ON(!coresight_trace_id_is_used(id));

	}

Anyways, for this patch:

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