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

Fan Ni
2025-03-03T18:04:34Z

On Fri, Feb 21, 2025 at 06:45:48PM +0530, Shradha Todi wrote:
> Add support to provide statistical counter interface to userspace. This set
> of debug registers are part of the RASDES feature present in DesignWare
> PCIe controllers.
>
One comment inline.
> Signed-off-by: Shradha Todi <shradha.t@samsung.com>
> ---
> Documentation/ABI/testing/debugfs-dwc-pcie | 61 +++++
> .../controller/dwc/pcie-designware-debugfs.c | 229 +++++++++++++++++-
> 2 files changed, 289 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/debugfs-dwc-pcie b/Documentation/ABI/testing/debugfs-dwc-pcie
> index 6ee0897fe753..650a89b0511e 100644
> --- a/Documentation/ABI/testing/debugfs-dwc-pcie
> +++ b/Documentation/ABI/testing/debugfs-dwc-pcie
> @@ -81,3 +81,64 @@ Description: rasdes_err_inj is the directory which can be used to inject errors
>
> <count>
> Number of errors to be injected

...

> +
> +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?

Fan
> +
> #define dwc_debugfs_create(name) \
> debugfs_create_file(#name, 0644, rasdes_debug, pci, \
> &dbg_ ## name ## _fops)
> @@ -249,6 +436,23 @@ static const struct file_operations dwc_pcie_err_inj_ops = {
> .write = err_inj_write,
> };
>
> +static const struct file_operations dwc_pcie_counter_enable_ops = {
> + .open = simple_open,
> + .read = counter_enable_read,
> + .write = counter_enable_write,
> +};
> +
> +static const struct file_operations dwc_pcie_counter_lane_ops = {
> + .open = simple_open,
> + .read = counter_lane_read,
> + .write = counter_lane_write,
> +};
> +
> +static const struct file_operations dwc_pcie_counter_value_ops = {
> + .open = simple_open,
> + .read = counter_value_read,
> +};
> +
> static void dwc_pcie_rasdes_debugfs_deinit(struct dw_pcie *pci)
> {
> struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
> @@ -258,7 +462,7 @@ static void dwc_pcie_rasdes_debugfs_deinit(struct dw_pcie *pci)
>
> static int dwc_pcie_rasdes_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
> {
> - struct dentry *rasdes_debug, *rasdes_err_inj;
> + struct dentry *rasdes_debug, *rasdes_err_inj, *rasdes_event_counter, *rasdes_events;
> struct dwc_pcie_rasdes_info *rasdes_info;
> struct dwc_pcie_rasdes_priv *priv_tmp;
> struct device *dev = pci->dev;
> @@ -277,6 +481,7 @@ static int dwc_pcie_rasdes_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
> /* Create subdirectories for Debug, Error injection, Statistics */
> rasdes_debug = debugfs_create_dir("rasdes_debug", dir);
> rasdes_err_inj = debugfs_create_dir("rasdes_err_inj", dir);
> + rasdes_event_counter = debugfs_create_dir("rasdes_event_counter", dir);
>
> mutex_init(&rasdes_info->reg_event_lock);
> rasdes_info->ras_cap_offset = ras_cap;
> @@ -299,6 +504,28 @@ static int dwc_pcie_rasdes_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
> debugfs_create_file(err_inj_list[i].name, 0200, rasdes_err_inj, priv_tmp,
> &dwc_pcie_err_inj_ops);
> }
> +
> + /* Create debugfs files for Statistical counter subdirectory */
> + for (i = 0; i < ARRAY_SIZE(event_list); i++) {
> + priv_tmp = devm_kzalloc(dev, sizeof(*priv_tmp), GFP_KERNEL);
> + if (!priv_tmp) {
> + ret = -ENOMEM;
> + goto err_deinit;
> + }
> +
> + priv_tmp->idx = i;
> + priv_tmp->pci = pci;
> + rasdes_events = debugfs_create_dir(event_list[i].name, rasdes_event_counter);
> + if (event_list[i].group_no == 0 || event_list[i].group_no == 4) {
> + debugfs_create_file("lane_select", 0644, rasdes_events,
> + priv_tmp, &dwc_pcie_counter_lane_ops);
> + }
> + debugfs_create_file("counter_value", 0444, rasdes_events, priv_tmp,
> + &dwc_pcie_counter_value_ops);
> + debugfs_create_file("counter_enable", 0644, rasdes_events, priv_tmp,
> + &dwc_pcie_counter_enable_ops);
> + }
> +
> return 0;
>
> err_deinit:
> --
> 2.17.1
>