Re: [PATCH v4 07/11] coresight-tpdm: Add nodes for dsb edge control

From: Suzuki K Poulose
Date: Fri Jun 02 2023 - 04:46:42 EST


On 02/06/2023 09:21, Tao Zhang wrote:

On 6/1/2023 8:14 PM, Suzuki K Poulose wrote:
On 27/04/2023 10:00, Tao Zhang wrote:
Add the nodes to set value for DSB edge control and DSB edge
control mask. Each DSB subunit TPDM has maximum of n(n<16) EDCR
resgisters to configure edge control. DSB edge detection control
00: Rising edge detection
01: Falling edge detection
10: Rising and falling edge detection (toggle detection)
And each DSB subunit TPDM has maximum of m(m<8) ECDMR registers to
configure mask. Eight 32 bit registers providing DSB interface
edge detection mask control.

Signed-off-by: Tao Zhang <quic_taozha@xxxxxxxxxxx>
---
  .../ABI/testing/sysfs-bus-coresight-devices-tpdm   |  32 +++++
  drivers/hwtracing/coresight/coresight-tpdm.c       | 135 ++++++++++++++++++++-
  drivers/hwtracing/coresight/coresight-tpdm.h       |  21 ++++
  3 files changed, 187 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
index 348e167..a57f000 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
@@ -60,3 +60,35 @@ Description:
          Bit[3] : Set to 0 for low performance mode.
                   Set to 1 for high performance mode.
          Bit[4:8] : Select byte lane for high performance mode.
+
+What: /sys/bus/coresight/devices/<tpdm-name>/dsb_edge_ctrl
+Date:        March 2023
+KernelVersion    6.3
+Contact:    Jinlong Mao (QUIC) <quic_jinlmao@xxxxxxxxxxx>, Tao Zhang (QUIC) <quic_taozha@xxxxxxxxxxx>
+Description:
+        Read/Write a set of the edge control registers of the DSB
+        in TPDM.
+
+        Expected format is the following:
+        <integer1> <integer2> <integer3>
+
+        Where:
+        <integer1> : Start EDCR register number
+        <integer2> : End EDCR register number
+        <integer3> : The value need to be written
+
+What: /sys/bus/coresight/devices/<tpdm-name>/dsb_edge_ctrl_mask
+Date:        March 2023
+KernelVersion    6.3
+Contact:    Jinlong Mao (QUIC) <quic_jinlmao@xxxxxxxxxxx>, Tao Zhang (QUIC) <quic_taozha@xxxxxxxxxxx>
+Description:
+        Read/Write a set of the edge control mask registers of the
+        DSB in TPDM.
+
+        Expected format is the following:
+        <integer1> <integer2> <integer3>
+
+        Where:
+        <integer1> : Start EDCMR register number
+        <integer2> : End EDCMR register number
+        <integer3> : The value need to be written
diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
index 1bacaa5..a40e458 100644
--- a/drivers/hwtracing/coresight/coresight-tpdm.c
+++ b/drivers/hwtracing/coresight/coresight-tpdm.c
@@ -80,7 +80,14 @@ static void set_trigger_type(struct tpdm_drvdata *drvdata, u32 *val)
    static void tpdm_enable_dsb(struct tpdm_drvdata *drvdata)
  {
-    u32 val;
+    u32 val, i;
+
+    for (i = 0; i < TPDM_DSB_MAX_EDCR; i++)
+        writel_relaxed(drvdata->dsb->edge_ctrl[i],
+               drvdata->base + TPDM_DSB_EDCR(i));
+    for (i = 0; i < TPDM_DSB_MAX_EDCMR; i++)
+        writel_relaxed(drvdata->dsb->edge_ctrl_mask[i],
+               drvdata->base + TPDM_DSB_EDCMR(i));

Do all TPDM DSBs have MAX_EDCR registers ? Or some have less than that ?
If it is latter, do we need special care to avoid writing to inexistent
registers ?

You are right, not all DSB TPDMs have MAX_EDCR registers. In our design, the inexistent register addresses

are not occupied and safe for accessing.

Currently we don't have a good way to know the quantity of EDCR/EDCMR registers for DSB TPDMs.

The only way we can think of is to set it in device tree manually.

Do you have other suggestion for this?

        val = readl_relaxed(drvdata->base + TPDM_DSB_TIER);
      /* Set trigger timestamp */
@@ -313,6 +320,130 @@ static ssize_t dsb_mode_store(struct device *dev,
  }
  static DEVICE_ATTR_RW(dsb_mode);
  +static ssize_t dsb_edge_ctrl_show(struct device *dev,
+                       struct device_attribute *attr,
+                       char *buf)
+{
+    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+    ssize_t size = 0;
+    int i;
+
+    spin_lock(&drvdata->spinlock);
+    for (i = 0; i < TPDM_DSB_MAX_EDCR; i++) {
+        size += sysfs_emit_at(buf, size,
+                  "Index:0x%x Val:0x%x\n", i,
+                  drvdata->dsb->edge_ctrl[i]);

It may be safe, but please add a check to make sure that we don't
overflow. At least bail out when we hit a return of 0, indicating
reached the end of buffer.

Can I add the following check to replace the current code??

int ret = 0;


for (i = 0; i < TPDM_DSB_MAX_EDCR; i++) {

    ret = sysfs_emit_at(buf, size, "Index:0x%x Val:0x%x\n", i, drvdata->dsb->edge_ctrl[i]);

    if (!ret) {

        dev_warn(drvdata->dev, "The buffer has been overflowed\n");

You don't need this, it already triggers a WARN() in sysfs_emit_at().
So you could do:

for (....) {
unsigned long bytes = sysfs_emit_at(buf, size, ....);

if (bytes <= 0)
break;
size += bytes;
}



        spin_unlock(&drvdata->spinlock);

        return size;

    } else

        size += ret;

}

+    }
+    spin_unlock(&drvdata->spinlock);
+    return size;
+}
+
+/*
+ * value 1: Start EDCR register number
+ * value 2: End EDCR register number
+ * value 3: The value need to be written
+ * The EDCR registers can include up to 16 32-bit registers, and each
+ * one can be configured to control up to 16 edge detections(2 bits
+ * control one edge detection). So a total 256 edge detections can be
+ * configured. So the starting number(value 1) and ending number(value 2)
+ * cannot be greater than 256, and value 1 should be less than value 2.
+ * The following values are the rage of value 3.
+ * 0 - Rising edge detection
+ * 1 - Falling edge detection
+ * 2 - Rising and falling edge detection (toggle detection)
+ */
+static ssize_t dsb_edge_ctrl_store(struct device *dev,
+                    struct device_attribute *attr,
+                    const char *buf,
+                    size_t size)
+{
+    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+    unsigned long val, mask, start, end, edge_ctrl, edge_ctrl_shift;
+    int i, reg;
+
+    if (sscanf(buf, "%lx %lx %lx", &start, &end, &edge_ctrl) != 3)
+        return -EINVAL;
+    if ((start >= TPDM_DSB_MAX_LINES) || (end >= TPDM_DSB_MAX_LINES) ||
+        (start > end) || (edge_ctrl > 0x2))
+        return -EPERM;
+
+    spin_lock(&drvdata->spinlock);
+    for (i = start; i <= end; i++) {
+        /*
+         * There are 2 bit per DSB Edge Control line.
+         * Thus we have 16 lines in a 32bit word.
+         */
+        reg = EDCR_TO_WORD_IDX(i);
+        mask = EDCR_TO_WORD_MASK(i);
+        val = drvdata->dsb->edge_ctrl[reg];

+        edge_ctrl_shift = EDCR_TO_WORD_VAL(edge_ctrl, i);
+        bitmap_replace(&val, &val, &edge_ctrl_shift, &mask, 32);

Could we simply do :

        reg &= ~mask;
        reg |= FIELD_PREP(mask, edge_ctrl);

Perhaps "FIELD_PREP" cannot be used here since "mask" must be constant in this macro.

Ah, you are right. Sorry about that.


But in our code, the variable "mask" is not constant.

Still I think using the bitmap_replace is an overkill. We could simply
do:
val &= ~mask;
val |= EDCR_TO_WORD_VAL(edge_ctrl, i);

Suzuki


+ drvdata->dsb->edge_ctrl[reg] = val;
+    }
+    spin_unlock(&drvdata->spinlock);
+
+    return size;
+}
+static DEVICE_ATTR_RW(dsb_edge_ctrl);
+
+static ssize_t dsb_edge_ctrl_mask_show(struct device *dev,
+                        struct device_attribute *attr,
+                        char *buf)
+{
+    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+    ssize_t size = 0;
+    int i;
+
+    spin_lock(&drvdata->spinlock);
+    for (i = 0; i < TPDM_DSB_MAX_EDCMR; i++) {
+        size += sysfs_emit_at(buf, size,
+                  "Index:0x%x Val:0x%x\n", i,
+                  drvdata->dsb->edge_ctrl_mask[i]);
+    }
+    spin_unlock(&drvdata->spinlock);
+    return size;
+}
+
+/*
+ * value 1: Start EDCMR register number
+ * value 2: End EDCMR register number
+ * value 3: The value need to be written
+ */
+static ssize_t dsb_edge_ctrl_mask_store(struct device *dev,
+                         struct device_attribute *attr,
+                         const char *buf,
+                         size_t size)
+{
+    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+    unsigned long start, end, val;
+    u32 set;
+    int i, reg;
+
+    if (sscanf(buf, "%lx %lx %lx", &start, &end, &val) != 3)
+        return -EINVAL;
+    if ((start >= TPDM_DSB_MAX_LINES) || (end >= TPDM_DSB_MAX_LINES)
+        || (start > end) || (val & ~1UL))
+        return -EPERM;
+
+    spin_lock(&drvdata->spinlock);
+    for (i = start; i <= end; i++) {
+        /*
+         * There is 1 bit per DSB Edge Control Mark line.
+         * Thus we have 32 lines in a 32bit word.
+         */
+        reg = EDCMR_TO_WORD_IDX(i);
+        set = drvdata->dsb->edge_ctrl_mask[reg];
+        if (val)
+            set |= BIT(EDCR_TO_WORD_SHIFT(i));
+        else
+            set &= ~BIT(EDCR_TO_WORD_SHIFT(i));
+        drvdata->dsb->edge_ctrl_mask[reg] = set;
+    }
+    spin_unlock(&drvdata->spinlock);
+    return size;
+}
+static DEVICE_ATTR_RW(dsb_edge_ctrl_mask);
+
  static ssize_t dsb_trig_type_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
  {
@@ -385,6 +516,8 @@ static DEVICE_ATTR_RW(dsb_trig_ts);
    static struct attribute *tpdm_dsb_attrs[] = {
      &dev_attr_dsb_mode.attr,
+    &dev_attr_dsb_edge_ctrl.attr,
+    &dev_attr_dsb_edge_ctrl_mask.attr,
      &dev_attr_dsb_trig_ts.attr,
      &dev_attr_dsb_trig_type.attr,
      NULL,
diff --git a/drivers/hwtracing/coresight/coresight-tpdm.h b/drivers/hwtracing/coresight/coresight-tpdm.h
index 79df07e..f25dcdec 100644
--- a/drivers/hwtracing/coresight/coresight-tpdm.h
+++ b/drivers/hwtracing/coresight/coresight-tpdm.h
@@ -12,6 +12,8 @@
  /* DSB Subunit Registers */
  #define TPDM_DSB_CR        (0x780)
  #define TPDM_DSB_TIER        (0x784)
+#define TPDM_DSB_EDCR(n)    (0x808 + (n * 4))
+#define TPDM_DSB_EDCMR(n)    (0x848 + (n * 4))
    /* Enable bit for DSB subunit */
  #define TPDM_DSB_CR_ENA        BIT(0)
@@ -34,6 +36,15 @@
  #define TPDM_DSB_TEST_MODE        GENMASK(10, 9)
  #define TPDM_DSB_HPSEL        GENMASK(6, 2)
  +#define EDCRS_PER_WORD                16
+#define EDCR_TO_WORD_IDX(r)            ((r) / EDCRS_PER_WORD)
+#define EDCR_TO_WORD_SHIFT(r)        ((r % EDCRS_PER_WORD) * 2)
+#define EDCR_TO_WORD_VAL(val, r)    (val << EDCR_TO_WORD_SHIFT(r))
+#define EDCR_TO_WORD_MASK(r)        EDCR_TO_WORD_VAL(0x3, r)

minor nit: add a new line here please
Sure, I will update this in the next patch series.

+#define EDCMRS_PER_WORD                32
+#define EDCMR_TO_WORD_IDX(r)        ((r) / EDCMRS_PER_WORD)
+#define EDCMR_TO_WORD_SHIFT(r)        ((r) % EDCMRS_PER_WORD)
+
  /* TPDM integration test registers */
  #define TPDM_ITATBCNTRL        (0xEF0)
  #define TPDM_ITCNTRL        (0xF00)
@@ -60,14 +71,24 @@
  #define TPDM_PIDR0_DS_IMPDEF    BIT(0)
  #define TPDM_PIDR0_DS_DSB    BIT(1)
  +#define TPDM_DSB_MAX_LINES    256
+/* MAX number of EDCR registers */
+#define TPDM_DSB_MAX_EDCR    16
+/* MAX number of EDCMR registers */
+#define TPDM_DSB_MAX_EDCMR    8
+
  /**
   * struct dsb_dataset - specifics associated to dsb dataset
   * @mode:             DSB programming mode
+ * @edge_ctrl:        Save value for edge control
+ * @edge_ctrl_mask:   Save value for edge control mask
   * @trig_ts:          Enable/Disable trigger timestamp.
   * @trig_type:        Enable/Disable trigger type.
   */
  struct dsb_dataset {
      u32                mode;
+    u32                edge_ctrl[TPDM_DSB_MAX_EDCR];
+    u32                edge_ctrl_mask[TPDM_DSB_MAX_EDCMR];

minor nit: Please align it with the fields below.

Sure, I will update this in the next patch series.


Best,

Tao


      bool            trig_ts;
      bool            trig_type;
  };

Suzuki