thunderbolt: Improve software receiver lane margining

USB4 specification defines the metadata needed to perform software
margining, as well as the necessary steps which include waiting for
dwell time.

- Add dwell_time attribute to set the wait time while performing
  margining and checking for link errors.
- Add error_counter attribute to configure error counter prior to
  margining test.
- Add voltage_time_offset attribute to set the voltage or time offset
  steps before performing the software margining test.
- Perform software margining test for dwell duration, break if there are
  link errors, stop the clocks and provide results.

Below is a minimalistic example how this can be used. Note these values
are just examples. The exact values in practice depend on host specific
capabilities and the type of measurement to be performed.

  # cd /sys/kernel/debug/thunderbolt/ROUTER/portX/margining/
  # echo software > mode
  # echo 400 > dwell_time
  # echo 1 > run

As usual the results attribute contains the results of a succesfull run.

Signed-off-by: R Kannappan <r.kannappan@intel.com>
Co-developed-by: Rene Sapiens <rene.sapiens@intel.com>
Signed-off-by: Rene Sapiens <rene.sapiens@intel.com>
Co-developed-by: Aapo Vienamo <aapo.vienamo@linux.intel.com>
Signed-off-by: Aapo Vienamo <aapo.vienamo@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

diff --git a/drivers/thunderbolt/debugfs.c b/drivers/thunderbolt/debugfs.c
index 9defa69ef3a7a2f7655bd7fa1d0daea6ff3b4b86..350310bd0feea70656f6c18f28906c59c5acfea7 100644 (file)
--- a/drivers/thunderbolt/debugfs.c
+++ b/drivers/thunderbolt/debugfs.c
@@ -9,6 +9,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/debugfs.h>
+#include <linux/delay.h>
 #include <linux/pm_runtime.h>
 #include <linux/uaccess.h>
 
@@ -34,6 +35,14 @@
 
 #define COUNTER_SET_LEN                3
 
+/*
+ * USB4 spec doesn't specify dwell range, the range of 100 ms to 500 ms
+ * probed to give good results.
+ */
+#define MIN_DWELL_TIME         100 /* ms */
+#define MAX_DWELL_TIME         500 /* ms */
+#define DWELL_SAMPLE_INTERVAL  10
+
 /* Sideband registers and their sizes as defined in the USB4 spec */
 struct sb_reg {
        unsigned int reg;
@@ -399,6 +408,9 @@ out:
  *                                     range (in mV).
  * @time_steps: Number of time margin steps
  * @max_time_offset: Maximum time margin offset (in mUI)
+ * @voltage_time_offset: Offset for voltage / time for software margining
+ * @dwell_time: Dwell time for software margining (in ms)
+ * @error_counter: Error counter operation for software margining
  * @optional_voltage_offset_range: Enable optional extended voltage range
  * @software: %true if software margining is used instead of hardware
  * @time: %true if time margining is used instead of voltage
@@ -422,12 +434,33 @@ struct tb_margining {
        unsigned int max_voltage_offset_optional_range;
        unsigned int time_steps;
        unsigned int max_time_offset;
+       unsigned int voltage_time_offset;
+       unsigned int dwell_time;
+       enum usb4_margin_sw_error_counter error_counter;
        bool optional_voltage_offset_range;
        bool software;
        bool time;
        bool right_high;
 };
 
+static int margining_modify_error_counter(struct tb_margining *margining,
+       u32 lanes, enum usb4_margin_sw_error_counter error_counter)
+{
+       struct usb4_port_margining_params params = { 0 };
+       struct tb_port *port = margining->port;
+       u32 result;
+
+       if (error_counter != USB4_MARGIN_SW_ERROR_COUNTER_CLEAR &&
+           error_counter != USB4_MARGIN_SW_ERROR_COUNTER_STOP)
+               return -EOPNOTSUPP;
+
+       params.error_counter = error_counter;
+       params.lanes = lanes;
+
+       return usb4_port_sw_margin(port, margining->target, margining->index,
+                                  &params, &result);
+}
+
 static bool supports_software(const struct tb_margining *margining)
 {
        return margining->caps[0] & USB4_MARGIN_CAP_0_MODES_SW;
@@ -689,9 +722,165 @@ static int margining_lanes_show(struct seq_file *s, void *not_used)
 DEBUGFS_ATTR_RW(margining_lanes);
 
 static ssize_t
-margining_optional_voltage_offset_write(struct file *file,
-                                  const char __user *user_buf,
-                                  size_t count, loff_t *ppos)
+margining_voltage_time_offset_write(struct file *file,
+                                   const char __user *user_buf,
+                                   size_t count, loff_t *ppos)
+{
+       struct seq_file *s = file->private_data;
+       struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+       unsigned int max_margin;
+       unsigned int val;
+       int ret;
+
+       ret = kstrtouint_from_user(user_buf, count, 10, &val);
+       if (ret)
+               return ret;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               if (margining->time)
+                       max_margin = margining->time_steps;
+               else
+                       if (margining->optional_voltage_offset_range)
+                               max_margin = margining->voltage_steps_optional_range;
+                       else
+                               max_margin = margining->voltage_steps;
+
+               margining->voltage_time_offset = clamp(val, 0, max_margin);
+       }
+
+       return count;
+}
+
+static int margining_voltage_time_offset_show(struct seq_file *s,
+                                             void *not_used)
+{
+       const struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               seq_printf(s, "%d\n", margining->voltage_time_offset);
+       }
+
+       return 0;
+}
+DEBUGFS_ATTR_RW(margining_voltage_time_offset);
+
+static ssize_t
+margining_error_counter_write(struct file *file, const char __user *user_buf,
+                             size_t count, loff_t *ppos)
+{
+       enum usb4_margin_sw_error_counter error_counter;
+       struct seq_file *s = file->private_data;
+       struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+       char *buf;
+
+       buf = validate_and_copy_from_user(user_buf, &count);
+       if (IS_ERR(buf))
+               return PTR_ERR(buf);
+
+       buf[count - 1] = '\0';
+
+       if (!strcmp(buf, "nop"))
+               error_counter = USB4_MARGIN_SW_ERROR_COUNTER_NOP;
+       else if (!strcmp(buf, "clear"))
+               error_counter = USB4_MARGIN_SW_ERROR_COUNTER_CLEAR;
+       else if (!strcmp(buf, "start"))
+               error_counter = USB4_MARGIN_SW_ERROR_COUNTER_START;
+       else if (!strcmp(buf, "stop"))
+               error_counter = USB4_MARGIN_SW_ERROR_COUNTER_STOP;
+       else
+               return -EINVAL;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               margining->error_counter = error_counter;
+       }
+
+       return count;
+}
+
+static int margining_error_counter_show(struct seq_file *s, void *not_used)
+{
+       const struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               switch (margining->error_counter) {
+               case USB4_MARGIN_SW_ERROR_COUNTER_NOP:
+                       seq_puts(s, "[nop] clear start stop\n");
+                       break;
+               case USB4_MARGIN_SW_ERROR_COUNTER_CLEAR:
+                       seq_puts(s, "nop [clear] start stop\n");
+                       break;
+               case USB4_MARGIN_SW_ERROR_COUNTER_START:
+                       seq_puts(s, "nop clear [start] stop\n");
+                       break;
+               case USB4_MARGIN_SW_ERROR_COUNTER_STOP:
+                       seq_puts(s, "nop clear start [stop]\n");
+                       break;
+               }
+       }
+
+       return 0;
+}
+DEBUGFS_ATTR_RW(margining_error_counter);
+
+static ssize_t
+margining_dwell_time_write(struct file *file, const char __user *user_buf,
+                          size_t count, loff_t *ppos)
+{
+       struct seq_file *s = file->private_data;
+       struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+       unsigned int val;
+       int ret;
+
+       ret = kstrtouint_from_user(user_buf, count, 10, &val);
+       if (ret)
+               return ret;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               margining->dwell_time = clamp(val, MIN_DWELL_TIME, MAX_DWELL_TIME);
+       }
+
+       return count;
+}
+
+static int margining_dwell_time_show(struct seq_file *s, void *not_used)
+{
+       struct tb_margining *margining = s->private;
+       struct tb *tb = margining->port->sw->tb;
+
+       scoped_cond_guard(mutex_intr, return -ERESTARTSYS, &tb->lock) {
+               if (!margining->software)
+                       return -EOPNOTSUPP;
+
+               seq_printf(s, "%d\n", margining->dwell_time);
+       }
+
+       return 0;
+}
+DEBUGFS_ATTR_RW(margining_dwell_time);
+
+static ssize_t
+margining_optional_voltage_offset_write(struct file *file, const char __user *user_buf,
+                                       size_t count, loff_t *ppos)
 {
        struct seq_file *s = file->private_data;
        struct tb_margining *margining = s->private;
@@ -796,6 +985,51 @@ static int margining_mode_show(struct seq_file *s, void *not_used)
 }
 DEBUGFS_ATTR_RW(margining_mode);
 
+static int margining_run_sw(struct tb_margining *margining,
+                           struct usb4_port_margining_params *params)
+{
+       u32 nsamples = margining->dwell_time / DWELL_SAMPLE_INTERVAL;
+       int ret, i;
+
+       ret = usb4_port_sw_margin(margining->port, margining->target, margining->index,
+                                 params, margining->results);
+       if (ret)
+               goto out_stop;
+
+       for (i = 0; i <= nsamples; i++) {
+               u32 errors = 0;
+
+               ret = usb4_port_sw_margin_errors(margining->port, margining->target,
+                                                margining->index, &margining->results[1]);
+               if (ret)
+                       break;
+
+               if (margining->lanes == USB4_MARGIN_SW_LANE_0)
+                       errors = FIELD_GET(USB4_MARGIN_SW_ERR_COUNTER_LANE_0_MASK,
+                                          margining->results[1]);
+               else if (margining->lanes == USB4_MARGIN_SW_LANE_1)
+                       errors = FIELD_GET(USB4_MARGIN_SW_ERR_COUNTER_LANE_1_MASK,
+                                          margining->results[1]);
+               else if (margining->lanes == USB4_MARGIN_SW_ALL_LANES)
+                       errors = margining->results[1];
+
+               /* Any errors stop the test */
+               if (errors)
+                       break;
+
+               fsleep(DWELL_SAMPLE_INTERVAL * USEC_PER_MSEC);
+       }
+
+out_stop:
+       /*
+        * Stop the counters but don't clear them to allow the
+        * different error counter configurations.
+        */
+       margining_modify_error_counter(margining, margining->lanes,
+                                      USB4_MARGIN_SW_ERROR_COUNTER_STOP);
+       return ret;
+}
+
 static int margining_run_write(void *data, u64 val)
 {
        struct tb_margining *margining = data;
@@ -836,11 +1070,15 @@ static int margining_run_write(void *data, u64 val)
                clx = ret;
        }
 
+       /* Clear the results */
+       memset(margining->results, 0, sizeof(margining->results));
+
        if (margining->software) {
                struct usb4_port_margining_params params = {
                        .error_counter = USB4_MARGIN_SW_ERROR_COUNTER_CLEAR,
                        .lanes = margining->lanes,
                        .time = margining->time,
+                       .voltage_time_offset = margining->voltage_time_offset,
                        .right_high = margining->right_high,
                        .optional_voltage_offset_range = margining->optional_voltage_offset_range,
                };
@@ -850,14 +1088,7 @@ static int margining_run_write(void *data, u64 val)
                            margining->time ? "time" : "voltage", dev_name(dev),
                            margining->lanes);
 
-               ret = usb4_port_sw_margin(port, margining->target, margining->index, &params,
-                                         &margining->results[0]);
-               if (ret)
-                       goto out_clx;
-
-               ret = usb4_port_sw_margin_errors(port, margining->target,
-                                                margining->index,
-                                                &margining->results[0]);
+               ret = margining_run_sw(margining, &params);
        } else {
                struct usb4_port_margining_params params = {
                        .ber_level = margining->ber_level,
@@ -867,10 +1098,6 @@ static int margining_run_write(void *data, u64 val)
                        .optional_voltage_offset_range = margining->optional_voltage_offset_range,
                };
 
-               /* Clear the results */
-               margining->results[0] = 0;
-               margining->results[1] = 0;
-
                tb_port_dbg(port,
                            "running hardware %s lane margining for %s lanes %u\n",
                            margining->time ? "time" : "voltage", dev_name(dev),
@@ -880,7 +1107,6 @@ static int margining_run_write(void *data, u64 val)
                                          margining->results);
        }
 
-out_clx:
        if (down_sw)
                tb_switch_clx_enable(down_sw, clx);
 out_unlock:
@@ -909,6 +1135,13 @@ static ssize_t margining_results_write(struct file *file,
        margining->results[0] = 0;
        margining->results[1] = 0;
 
+       if (margining->software) {
+               /* Clear the error counters */
+               margining_modify_error_counter(margining,
+                                              USB4_MARGIN_SW_ALL_LANES,
+                                              USB4_MARGIN_SW_ERROR_COUNTER_CLEAR);
+       }
+
        mutex_unlock(&tb->lock);
        return count;
 }
@@ -998,6 +1231,24 @@ static int margining_results_show(struct seq_file *s, void *not_used)
                                voltage_margin_show(s, margining, val);
                        }
                }
+       } else {
+               u32 lane_errors, result;
+
+               seq_printf(s, "0x%08x\n", margining->results[1]);
+               result = FIELD_GET(USB4_MARGIN_SW_LANES_MASK, margining->results[0]);
+
+               if (result == USB4_MARGIN_SW_LANE_0 ||
+                   result == USB4_MARGIN_SW_ALL_LANES) {
+                       lane_errors = FIELD_GET(USB4_MARGIN_SW_ERR_COUNTER_LANE_0_MASK,
+                                               margining->results[1]);
+                       seq_printf(s, "# lane 0 errors: %u\n", lane_errors);
+               }
+               if (result == USB4_MARGIN_SW_LANE_1 ||
+                   result == USB4_MARGIN_SW_ALL_LANES) {
+                       lane_errors = FIELD_GET(USB4_MARGIN_SW_ERR_COUNTER_LANE_1_MASK,
+                                               margining->results[1]);
+                       seq_printf(s, "# lane 1 errors: %u\n", lane_errors);
+               }
        }
 
        mutex_unlock(&tb->lock);
@@ -1211,9 +1462,21 @@ static struct tb_margining *margining_alloc(struct tb_port *port,
                debugfs_create_file("margin", 0600, dir, margining,
                                    &margining_margin_fops);
 
+       margining->error_counter = USB4_MARGIN_SW_ERROR_COUNTER_CLEAR;
+       margining->dwell_time = MIN_DWELL_TIME;
+
        if (supports_optional_voltage_offset_range(margining))
                debugfs_create_file("optional_voltage_offset", DEBUGFS_MODE, dir, margining,
                                    &margining_optional_voltage_offset_fops);
+
+       if (supports_software(margining)) {
+               debugfs_create_file("voltage_time_offset", DEBUGFS_MODE, dir, margining,
+                                   &margining_voltage_time_offset_fops);
+               debugfs_create_file("error_counter", DEBUGFS_MODE, dir, margining,
+                                   &margining_error_counter_fops);
+               debugfs_create_file("dwell_time", DEBUGFS_MODE, dir, margining,
+                                   &margining_dwell_time_fops);
+       }
        return margining;
 }
 

diff --git a/drivers/thunderbolt/sb_regs.h b/drivers/thunderbolt/sb_regs.h
index 8bff0740222c51a7f7c8730ab9f0a7b7249ae015..dbcad25ead50f1687b253499b8ed0693c3f0a90a 100644 (file)
--- a/drivers/thunderbolt/sb_regs.h
+++ b/drivers/thunderbolt/sb_regs.h
@@ -86,9 +86,17 @@ enum usb4_sb_opcode {
 #define USB4_MARGIN_HW_RES_1_L1_LL_MARGIN_SHIFT        24
 
 /* USB4_SB_OPCODE_RUN_SW_LANE_MARGINING */
+#define USB4_MARGIN_SW_LANES_MASK              GENMASK(2, 0)
+#define USB4_MARGIN_SW_LANE_0                  0x0
+#define USB4_MARGIN_SW_LANE_1                  0x1
+#define USB4_MARGIN_SW_ALL_LANES               0x7
 #define USB4_MARGIN_SW_TIME                    BIT(3)
 #define USB4_MARGIN_SW_RH                      BIT(4)
 #define USB4_MARGIN_SW_OPT_VOLTAGE             BIT(5)
+#define USB4_MARGIN_SW_VT_MASK                 GENMASK(12, 6)
 #define USB4_MARGIN_SW_COUNTER_MASK            GENMASK(14, 13)
 
+#define USB4_MARGIN_SW_ERR_COUNTER_LANE_0_MASK GENMASK(3, 0)
+#define USB4_MARGIN_SW_ERR_COUNTER_LANE_1_MASK GENMASK(7, 4)
+
 #endif

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 262c333924b8391ba6d8a3f15597c6a947a58c92..6737188f25815748118a0316e74092531e855343 100644 (file)
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -1372,6 +1372,7 @@ enum usb4_margin_sw_error_counter {
  * @error_counter: Error counter operation for software margining
  * @ber_level: Current BER level contour value
  * @lanes: %0, %1 or %7 (all)
+ * @voltage_time_offset: Offset for voltage / time for software margining
  * @optional_voltage_offset_range: Enable optional extended voltage range
  * @right_high: %false if left/low margin test is performed, %true if right/high
  * @time: %true if time margining is used instead of voltage
@@ -1380,6 +1381,7 @@ struct usb4_port_margining_params {
        enum usb4_margin_sw_error_counter error_counter;
        u32 ber_level;
        u32 lanes;
+       u32 voltage_time_offset;
        bool optional_voltage_offset_range;
        bool right_high;
        bool time;

diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index a2f81e17ad8db88a8cbaca0513f92729425c4b5d..0a9b4aeb3fa140f2bcfdbb03a4e27426e6c7f8f2 100644 (file)
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -1723,6 +1723,7 @@ int usb4_port_sw_margin(struct tb_port *port, enum usb4_sb_target target,
        if (params->right_high)
                val |= USB4_MARGIN_SW_RH;
        val |= FIELD_PREP(USB4_MARGIN_SW_COUNTER_MASK, params->error_counter);
+       val |= FIELD_PREP(USB4_MARGIN_SW_VT_MASK, params->voltage_time_offset);
 
        ret = usb4_port_sb_write(port, target, index, USB4_SB_METADATA, &val,
                                 sizeof(val));