linux-kernel - Re: [PATCH v1 3/3] coresight: tpda: add sysfs node to flush specific port

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Message-ID: <3ac2954e-5663-4ea0-bc1d-a09e1992af5b@linaro.org>
Date: Tue, 26 Aug 2025 10:27:45 +0100
From: James Clark <james.clark@...aro.org>
To: Jie Gan <jie.gan@....qualcomm.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Tingwei Zhang <tingwei.zhang@....qualcomm.com>
Subject: Re: [PATCH v1 3/3] coresight: tpda: add sysfs node to flush specific
 port



On 26/08/2025 8:01 am, Jie Gan wrote:
> From: Tao Zhang <tao.zhang@....qualcomm.com>
> 
> Setting bit i in the TPDA_FLUSH_CR register initiates a flush request
> for port i, forcing the data to synchronize and be transmitted to the
> sink device.
> 
> Signed-off-by: Tao Zhang <tao.zhang@....qualcomm.com>
> Co-developed-by: Jie Gan <jie.gan@....qualcomm.com>
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
> ---
>   .../testing/sysfs-bus-coresight-devices-tpda  |  7 +++
>   drivers/hwtracing/coresight/coresight-tpda.c  | 45 +++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-tpda.h  |  1 +
>   3 files changed, 53 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> index e827396a0fa1..8803158ba42f 100644
> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> @@ -41,3 +41,10 @@ Contact:	Jinlong Mao <jinlong.mao@....qualcomm.com>, Tao Zhang <tao.zhang@....qu
>   Description:
>   		(RW) Configure the CMB/MCMB channel mode for all enabled ports.
>   		Value 0 means raw channel mapping mode. Value 1 means channel pair marking mode.
> +
> +What:		/sys/bus/coresight/devices/<tpda-name>/port_flush_req
> +Date:		August 2025
> +KernelVersion:	6.17
> +Contact:	Jinlong Mao <jinlong.mao@....qualcomm.com>, Tao Zhang <tao.zhang@....qualcomm.com>, Jie Gan <jie.gan@....qualcomm.com>
> +Description:
> +		(RW) Configure the bit i to requests a flush operation of port i on the TPDA.
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c
> index 9e623732d1e7..c5f169facc51 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.c
> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
> @@ -509,6 +509,50 @@ static ssize_t cmbchan_mode_store(struct device *dev,
>   }
>   static DEVICE_ATTR_RW(cmbchan_mode);
>   
> +static ssize_t port_flush_req_show(struct device *dev,
> +				   struct device_attribute *attr,
> +				   char *buf)
> +{
> +	struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +	unsigned long val;
> +
> +	guard(spinlock)(&drvdata->spinlock);
> +	if (!drvdata->csdev->refcnt)
> +		return -EPERM;
> +
> +	val = readl_relaxed(drvdata->base + TPDA_FLUSH_CR);
> +	return sysfs_emit(buf, "%lx\n", val);

Decimal would be better for a port number that goes from 0 - 127. If you 
really want to use hex then don't you need to prefix it with 0x? 
Otherwise you can't tell the difference between decimal 10 and hex 10, 
and it's not documented that it's hex either.

> +}
> +
> +static ssize_t port_flush_req_store(struct device *dev,
> +				    struct device_attribute *attr,
> +				    const char *buf,
> +				    size_t size)
> +{
> +	struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +	unsigned long val;
> +
> +	if (kstrtoul(buf, 0, &val))
> +		return -EINVAL;
> +
> +	/* The valid value ranges from 0 to 127 */
> +	if (val > 127)
> +		return -EINVAL;
> +
> +	guard(spinlock)(&drvdata->spinlock);
> +	if (!drvdata->csdev->refcnt)
> +		return -EPERM;
> +
> +	if (val) {

If 0 - 127 are valid don't you want to write 0 too?

> +		CS_UNLOCK(drvdata->base);
> +		writel_relaxed(val, drvdata->base + TPDA_FLUSH_CR);
> +		CS_LOCK(drvdata->base);
> +	}
> +
> +	return size;
> +}
> +static DEVICE_ATTR_RW(port_flush_req);
> +
>   static struct attribute *tpda_attrs[] = {
>   	&dev_attr_trig_async_enable.attr,
>   	&dev_attr_trig_flag_ts_enable.attr,
> @@ -516,6 +560,7 @@ static struct attribute *tpda_attrs[] = {
>   	&dev_attr_freq_ts_enable.attr,
>   	&dev_attr_global_flush_req.attr,
>   	&dev_attr_cmbchan_mode.attr,
> +	&dev_attr_port_flush_req.attr,
>   	NULL,
>   };
>   
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.h b/drivers/hwtracing/coresight/coresight-tpda.h
> index 00d146960d81..55a18d718357 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.h
> +++ b/drivers/hwtracing/coresight/coresight-tpda.h
> @@ -10,6 +10,7 @@
>   #define TPDA_Pn_CR(n)		(0x004 + (n * 4))
>   #define TPDA_FPID_CR		(0x084)
>   #define TPDA_SYNCR		(0x08C)
> +#define TPDA_FLUSH_CR		(0x090)
>   
>   /* Cross trigger FREQ packets timestamp bit */
>   #define TPDA_CR_FREQTS		BIT(2)