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

Shradha Todi
2025-02-22T10:59:28Z

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.

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
+
+What: /sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/counter_enable
+Date: Feburary 2025
+Contact: Shradha Todi <shradha.t@samsung.com>
+Description: rasdes_event_counters is the directory which can be used to collect
+ statistical data about the number of times a certain event has occurred
+ in the controller. The list of possible events are:
+
+ 1) EBUF Overflow
+ 2) EBUF Underrun
+ 3) Decode Error
+ 4) Running Disparity Error
+ 5) SKP OS Parity Error
+ 6) SYNC Header Error
+ 7) Rx Valid De-assertion
+ 8) CTL SKP OS Parity Error
+ 9) 1st Retimer Parity Error
+ 10) 2nd Retimer Parity Error
+ 11) Margin CRC and Parity Error
+ 12) Detect EI Infer
+ 13) Receiver Error
+ 14) RX Recovery Req
+ 15) N_FTS Timeout
+ 16) Framing Error
+ 17) Deskew Error
+ 18) Framing Error In L0
+ 19) Deskew Uncompleted Error
+ 20) Bad TLP
+ 21) LCRC Error
+ 22) Bad DLLP
+ 23) Replay Number Rollover
+ 24) Replay Timeout
+ 25) Rx Nak DLLP
+ 26) Tx Nak DLLP
+ 27) Retry TLP
+ 28) FC Timeout
+ 29) Poisoned TLP
+ 30) ECRC Error
+ 31) Unsupported Request
+ 32) Completer Abort
+ 33) Completion Timeout
+ 34) EBUF SKP Add
+ 35) EBUF SKP Del
+
+ (RW) Write 1 to enable the event counter and write 0 to disable the event counter.
+ Read will return whether the counter is currently enabled or disabled. Counter is
+ disabled by default.
+
+What: /sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/counter_value
+Date: Feburary 2025
+Contact: Shradha Todi <shradha.t@samsung.com>
+Description: (RO) Read will return the current value of the event counter. To reset the counter,
+ counter should be disabled and enabled back using the 'counter_enable' attribute.
+
+What: /sys/kernel/debug/dwc_pcie_<dev>/rasdes_event_counters/<event>/lane_select
+Date: Feburary 2025
+Contact: Shradha Todi <shradha.t@samsung.com>
+Description: (RW) Some lanes in the event list are lane specific events. These include
+ events 1) - 11) and 34) - 35).
+ Write lane number for which counter needs to be enabled/disabled/dumped.
+ Read will return the current selected lane number. Lane0 is selected by default.
diff --git a/drivers/pci/controller/dwc/pcie-designware-debugfs.c b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
index b7260edd2336..dca1e9999113 100644
--- a/drivers/pci/controller/dwc/pcie-designware-debugfs.c
+++ b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
@@ -31,6 +31,17 @@

#define ERR_INJ_ENABLE_REG 0x30

+#define RAS_DES_EVENT_COUNTER_DATA_REG 0xc
+
+#define RAS_DES_EVENT_COUNTER_CTRL_REG 0x8
+#define EVENT_COUNTER_GROUP_SELECT GENMASK(27, 24)
+#define EVENT_COUNTER_EVENT_SELECT GENMASK(23, 16)
+#define EVENT_COUNTER_LANE_SELECT GENMASK(11, 8)
+#define EVENT_COUNTER_STATUS BIT(7)
+#define EVENT_COUNTER_ENABLE GENMASK(4, 2)
+#define PER_EVENT_ON 0x3
+#define PER_EVENT_OFF 0x1
+
#define DWC_DEBUGFS_BUF_MAX 128

/**
@@ -113,6 +124,61 @@ static const u32 err_inj_type_mask[] = {
EINJ5_TYPE,
};

+/**
+ * struct dwc_pcie_event_counter - Store details about each event counter supported in DWC RASDES
+ * @name: Name of the error counter
+ * @group_no: Group number that the event belongs to. Value ranges from 0 - 4
+ * @event_no: Event number of the particular event. Value ranges from -
+ * Group 0: 0 - 10
+ * Group 1: 5 - 13
+ * Group 2: 0 - 7
+ * Group 3: 0 - 5
+ * Group 4: 0 - 1
+ */
+struct dwc_pcie_event_counter {
+ const char *name;
+ u32 group_no;
+ u32 event_no;
+};
+
+static const struct dwc_pcie_event_counter event_list[] = {
+ {"ebuf_overflow", 0x0, 0x0},
+ {"ebuf_underrun", 0x0, 0x1},
+ {"decode_err", 0x0, 0x2},
+ {"running_disparity_err", 0x0, 0x3},
+ {"skp_os_parity_err", 0x0, 0x4},
+ {"sync_header_err", 0x0, 0x5},
+ {"rx_valid_deassertion", 0x0, 0x6},
+ {"ctl_skp_os_parity_err", 0x0, 0x7},
+ {"retimer_parity_err_1st", 0x0, 0x8},
+ {"retimer_parity_err_2nd", 0x0, 0x9},
+ {"margin_crc_parity_err", 0x0, 0xA},
+ {"detect_ei_infer", 0x1, 0x5},
+ {"receiver_err", 0x1, 0x6},
+ {"rx_recovery_req", 0x1, 0x7},
+ {"n_fts_timeout", 0x1, 0x8},
+ {"framing_err", 0x1, 0x9},
+ {"deskew_err", 0x1, 0xa},
+ {"framing_err_in_l0", 0x1, 0xc},
+ {"deskew_uncompleted_err", 0x1, 0xd},
+ {"bad_tlp", 0x2, 0x0},
+ {"lcrc_err", 0x2, 0x1},
+ {"bad_dllp", 0x2, 0x2},
+ {"replay_num_rollover", 0x2, 0x3},
+ {"replay_timeout", 0x2, 0x4},
+ {"rx_nak_dllp", 0x2, 0x5},
+ {"tx_nak_dllp", 0x2, 0x6},
+ {"retry_tlp", 0x2, 0x7},
+ {"fc_timeout", 0x3, 0x0},
+ {"poisoned_tlp", 0x3, 0x1},
+ {"ecrc_error", 0x3, 0x2},
+ {"unsupported_request", 0x3, 0x3},
+ {"completer_abort", 0x3, 0x4},
+ {"completion_timeout", 0x3, 0x5},
+ {"ebuf_skp_add", 0x4, 0x0},
+ {"ebuf_skp_del", 0x4, 0x1},
+};
+
static ssize_t lane_detect_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct dw_pcie *pci = file->private_data;
@@ -230,6 +296,127 @@ static ssize_t err_inj_write(struct file *file, const char __user *buf, size_t c
return count;
}

+static void set_event_number(struct dwc_pcie_rasdes_priv *pdata, struct dw_pcie *pci,
+ struct dwc_pcie_rasdes_info *rinfo)
+{
+ u32 val;
+
+ val = dw_pcie_readl_dbi(pci, rinfo->ras_cap_offset + RAS_DES_EVENT_COUNTER_CTRL_REG);
+ val &= ~EVENT_COUNTER_ENABLE;
+ val &= ~(EVENT_COUNTER_GROUP_SELECT | EVENT_COUNTER_EVENT_SELECT);
+ val |= FIELD_PREP(EVENT_COUNTER_GROUP_SELECT, event_list[pdata->idx].group_no);
+ val |= FIELD_PREP(EVENT_COUNTER_EVENT_SELECT, event_list[pdata->idx].event_no);
+ dw_pcie_writel_dbi(pci, rinfo->ras_cap_offset + RAS_DES_EVENT_COUNTER_CTRL_REG, val);
+}
+
+static ssize_t counter_enable_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_CTRL_REG);
+ mutex_unlock(&rinfo->reg_event_lock);
+ val = FIELD_GET(EVENT_COUNTER_STATUS, val);
+ if (val)
+ pos = scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX, "Counter Enabled\n");
+ else
+ pos = scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX, "Counter Disabled\n");
+
+ return simple_read_from_buffer(buf, count, ppos, debugfs_buf, pos);
+}
+
+static ssize_t counter_enable_write(struct file *file, const 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;
+ u32 val, enable;
+
+ val = kstrtou32_from_user(buf, count, 0, &enable);
+ if (val)
+ return 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_CTRL_REG);
+ if (enable)
+ val |= FIELD_PREP(EVENT_COUNTER_ENABLE, PER_EVENT_ON);
+ else
+ val |= FIELD_PREP(EVENT_COUNTER_ENABLE, PER_EVENT_OFF);
+
+ dw_pcie_writel_dbi(pci, rinfo->ras_cap_offset + RAS_DES_EVENT_COUNTER_CTRL_REG, val);
+ mutex_unlock(&rinfo->reg_event_lock);
+
+ return count;
+}
+
+static ssize_t counter_lane_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_CTRL_REG);
+ mutex_unlock(&rinfo->reg_event_lock);
+ val = FIELD_GET(EVENT_COUNTER_LANE_SELECT, val);
+ pos = scnprintf(debugfs_buf, DWC_DEBUGFS_BUF_MAX, "Lane: %d\n", val);
+
+ return simple_read_from_buffer(buf, count, ppos, debugfs_buf, pos);
+}
+
+static ssize_t counter_lane_write(struct file *file, const 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;
+ u32 val, lane;
+
+ val = kstrtou32_from_user(buf, count, 0, &lane);
+ if (val)
+ return 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_CTRL_REG);
+ val &= ~(EVENT_COUNTER_LANE_SELECT);
+ val |= FIELD_PREP(EVENT_COUNTER_LANE_SELECT, lane);
+ dw_pcie_writel_dbi(pci, rinfo->ras_cap_offset + RAS_DES_EVENT_COUNTER_CTRL_REG, val);
+ mutex_unlock(&rinfo->reg_event_lock);
+
+ return count;
+}
+
+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);
+}
+
#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