Re: [PATCH v5 3/3] coresight: tpda: add sysfs node to flush specific port

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 19/12/2025 10:04, Jie Gan wrote:
> From: Tao Zhang <tao.zhang@oss.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@oss.qualcomm.com>
> Reviewed-by: James Clark <james.clark@linaro.org>
> Co-developed-by: Jie Gan <jie.gan@oss.qualcomm.com>
> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
> ---
>   .../ABI/testing/sysfs-bus-coresight-devices-tpda   |  7 ++++
>   drivers/hwtracing/coresight/coresight-tpda.c       | 49 ++++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-tpda.h       |  1 +
>   3 files changed, 57 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpda
> index a7855922328e..ef2804f87d1e 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@oss.qualcomm.com>, Tao Zhang <tao.zhang@oss.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:		December 2025
> +KernelVersion:	6.19
> +Contact:	Jinlong Mao <jinlong.mao@oss.qualcomm.com>, Tao Zhang <tao.zhang@oss.qualcomm.com>, Jie Gan <jie.gan@oss.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 d378ff8ad77d..5b4a9e41b067 100644
> --- a/drivers/hwtracing/coresight/coresight-tpda.c
> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
> @@ -375,6 +375,45 @@ static ssize_t tpda_trig_sysfs_store(struct device *dev,
>   	return ret;
>   }
>   
> +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_global_cr_attrs[] = {
>   	tpda_trig_sysfs_rw(global_flush_req, FLREQ),
>   	tpda_trig_sysfs_rw(freq_ts_enable, FREQTS),
> @@ -385,13 +424,23 @@ static struct attribute *tpda_global_cr_attrs[] = {
>   	NULL,
>   };
>   
> +static struct attribute *tpda_attrs[] = {
> +	&dev_attr_port_flush_req.attr,
> +	NULL,
> +};
> +

But why ? Why can't this be a part of the tpda_global_cr_attrs[] ?
For that matter, why is tpda_global_cr_attrs named as such and why not
tpda_attrs ?

Suzuki

>   static struct attribute_group tpda_global_cr_attr_grp = {
>   	.attrs	= tpda_global_cr_attrs,
>   	.name	= "global_cr",
>   };
>   
> +static struct attribute_group tpda_attr_grp = {
> +	.attrs	= tpda_attrs,
> +};
> +
>   static const struct attribute_group *tpda_attr_grps[] = {
>   	&tpda_global_cr_attr_grp,
> +	&tpda_attr_grp,
>   	NULL,
>   };
>   
> diff --git a/drivers/hwtracing/coresight/coresight-tpda.h b/drivers/hwtracing/coresight/coresight-tpda.h
> index 97e2729c15c9..ec93f9cb9648 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)
>