Re: [PATCH v7 5/5] Add debugfs based statistical counter support in DWC

Manivannan Sadhasivam
2025-03-04T15:32:17Z

On Mon, Mar 03, 2025 at 01:03:12PM -0800, Fan Ni wrote:
> On Tue, Mar 04, 2025 at 04:42:28AM +0900, Krzysztof Wilczyński wrote:
> > Hello,
> >
> > [...]
> > > > +static ssize_t counter_value_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> > > > +{
> > > > + struct dwc_pcie_rasdes_priv *pdata = file->private_data;
> > > > + struct dw_pcie *pci = pdata->pci;
> > > > + struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> > > > + char debugfs_buf[DWC_DEBUGFS_BUF_MAX];
> > > > + ssize_t pos;
> > > > + u32 val;
> > > > +
> > > > + mutex_lock(&rinfo->reg_event_lock);
> > > > + set_event_number(pdata, pci, rinfo);
> > > > + val = dw_pcie_readl_dbi(pci, rinfo->ras_cap_offset + RAS_DES_EVENT_COUNTER_DATA_REG);
> > > > + mutex_unlock(&rinfo->reg_event_lock);
> > > > + pos = scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX, "Counter value: %d\n", val);
> > > > +
> > > > + return simple_read_from_buffer(buf, count, ppos, debugfs_buf, pos);
> > > > +}
> > >
> > > Do we need to check whether the counter is enabled or not for the event
> > > before retrieving the counter value?
> >
> > I believe, we have a patch that aims to address, have a look at:
> >
> > https://lore.kernel.org/linux-pci/20250225171239.19574-1-manivannan.sadhasivam@linaro.org
>
> Maybe I missed something, that seems to fix counter_enable_read(), but
> here is to retrieve counter value.
> How dw_pcie_readl_dbi() can return something like "Counter Disabled"?
>

Only way to know if a counter is enabled by reading back the status. And that is
what the patch is doing.

- Mani

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