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

[Jie Gan]

On 12/22/2025 9:12 PM, Suzuki K Poulose wrote:
> On 22/12/2025 06:02, Jie Gan wrote:
> > From: Tao Zhang <tao.zhang@xxxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxxx>
> > Reviewed-by: James Clark <james.clark@xxxxxxxxxx>
> > Co-developed-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > ---
> >   .../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@xxxxxxxxxxxxxxxx>, Tao Zhang 
> > <tao.zhang@xxxxxxxxxxxxxxxx>, Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > +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" ? 

Yes, global_flush_req triggers all ports at once, whereas this node 
initiates a flush request for specific port(s).

For reading, we can check whether the flush request has completed.

Thanks,
Jie

> 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)