linux-kernel - Re: [PATCH v6 4/4] coresight: tpda: add sysfs node to flush specific port

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Message-ID: <9899b6c2-2bdf-41b8-9156-dcf1b611da39@arm.com>
Date: Mon, 22 Dec 2025 13:12:45 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Jie Gan <jie.gan@....qualcomm.com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Tingwei Zhang <tingwei.zhang@....qualcomm.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Tao Zhang <tao.zhang@....qualcomm.com>
Subject: Re: [PATCH v6 4/4] coresight: tpda: add sysfs node to flush specific
 port

On 22/12/2025 06:02, 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>
> Reviewed-by: James Clark <james.clark@...aro.org>
> Co-developed-by: Jie Gan <jie.gan@....qualcomm.com>
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
> ---
>   .../ABI/testing/sysfs-bus-coresight-devices-tpda   |  7 ++++
>   drivers/hwtracing/coresight/coresight-tpda.c       | 40 ++++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-tpda.h       |  1 +
>   3 files changed, 48 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> index d359d90dca72..df8f03d4b573 100644
> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> @@ -51,3 +51,10 @@ Description:
>   		mode 0 - COUNT[11:0] value represents the approximate number of bytes moved between two ASYNC packet requests
>   		mode 1 - the bits COUNT[11:7] are used as a power of 2. for example, we could insert an async packet every 8K
>   		         data by writing a value 13 to the COUNT[11:7] field.
> +
> +What:		/sys/bus/coresight/devices/<tpda-name>/port_flush_req
> +Date:		December 2025
> +KernelVersion:	6.19
> +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.

Does this have similar semantics as the "global_flush_req"  for "Read" ? 
i.e., the bit stays set until the request completes ? Otherwise, why 
isn't this Write only ?

I don't see the point of "Reading" this value back.

Suzuki

> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c
> index 7baa8a0965d3..f79fea4fbb2c 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.c
> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
> @@ -430,9 +430,49 @@ static ssize_t syncr_mode_store(struct device *dev,
>   }
>   static DEVICE_ATTR_RW(syncr_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;
> +
> +	if (!drvdata->csdev->refcnt)
> +		return -EINVAL;
> +
> +	guard(spinlock)(&drvdata->spinlock);
> +	val = readl_relaxed(drvdata->base + TPDA_FLUSH_CR);
> +
> +	return sysfs_emit(buf, "0x%lx\n", val);
> +}
> +
> +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);
> +	u32 val;
> +
> +	if (kstrtou32(buf, 0, &val))
> +		return -EINVAL;
> +
> +	if (!drvdata->csdev->refcnt || !val)
> +		return -EINVAL;
> +
> +	guard(spinlock)(&drvdata->spinlock);
> +	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_global_flush_req.attr,
>   	&dev_attr_syncr_mode.attr,
> +	&dev_attr_port_flush_req.attr,
>   	tpda_trig_sysfs_rw(freq_ts_enable, FREQTS),
>   	tpda_trig_sysfs_rw(trig_freq_enable, FRIE),
>   	tpda_trig_sysfs_rw(trig_flag_ts_enable, FLRIE),
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.h b/drivers/hwtracing/coresight/coresight-tpda.h
> index 1d2de50bb9f9..ef1ce2ce36a9 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 global (all ports) flush request bit */
>   #define TPDA_CR_FLREQ		BIT(0)
>