RE: [EXTERNAL] Re: [PATCH v9 2/7] coresight: tmc-etr: Add support to use reserved trace memory

Hi Suzuki,

-----Original Message-----
From: Suzuki K Poulose <suzuki.poulose@arm.com>
Sent: Friday, June 7, 2024 9:28 PM
To: Linu Cherian <redacted>; mike.leach@linaro.org;
james.clark@arm.com
Cc: linux-arm-kernel@lists.infradead.org; coresight@lists.linaro.org; linux-
kernel@vger.kernel.org; robh+dt@kernel.org;
krzysztof.kozlowski+dt@linaro.org; conor+dt@kernel.org;
devicetree@vger.kernel.org; Sunil Kovvuri Goutham
[off-list ref]; George Cherian [off-list ref]; Anil
Kumar Reddy H [off-list ref]
Subject: [EXTERNAL] Re: [PATCH v9 2/7] coresight: tmc-etr: Add support to
use reserved trace memory

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Hi Linu

On 05/06/2024 09:17, Linu Cherian wrote:

quoted

Add support to use reserved memory for coresight ETR trace buffer.

Introduce a new ETR buffer mode called ETR_MODE_RESRV, which

becomes

quoted

available when ETR device tree node is supplied with a valid reserved
memory region.

ETR_MODE_RESRV can be selected only by explicit user request.

$ echo resrv
/sys/bus/coresight/devices/tmc_etr<N>/buf_mode_preferred

Signed-off-by: Anil Kumar Reddy <redacted>
Signed-off-by: Linu Cherian <redacted>
Reviewed-by: James Clark <redacted>

Some minor comments below.

quoted

---
Changelog from v8:
Added Reviewed-by tag.

  .../hwtracing/coresight/coresight-tmc-core.c  | 47 +++++++++++
  .../hwtracing/coresight/coresight-tmc-etr.c   | 79 +++++++++++++++++++
  drivers/hwtracing/coresight/coresight-tmc.h   | 27 +++++++
  3 files changed, 153 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c

b/drivers/hwtracing/coresight/coresight-tmc-core.c
index 741ce1748e75..6beb69d74d0a 100644

--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c

@@ -23,6 +23,7 @@
  #include <linux/spinlock.h>
  #include <linux/pm_runtime.h>
  #include <linux/of.h>
+#include <linux/of_address.h>
  #include <linux/coresight.h>
  #include <linux/amba/bus.h>
  #include <linux/platform_device.h>

@@ -400,6 +401,50 @@ static inline bool

tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)

  static const struct amba_id tmc_ids[];

+static struct device_node *tmc_get_region_byname(struct device_node

*node,

quoted

+						 char *name)
+{
+	int index;
+
+	index = of_property_match_string(node, "memory-region-names",

name);

quoted

+	if (index < 0)
+		return ERR_PTR(-ENODEV);
+
+	return of_parse_phandle(node, "memory-region", index); }
+
+static void tmc_get_reserved_region(struct device *parent) {
+	struct tmc_drvdata *drvdata = dev_get_drvdata(parent);
+	struct device_node *node;
+	struct resource res;
+	int rc;
+
+	node = tmc_get_region_byname(parent->of_node, "tracedata");
+	if (IS_ERR_OR_NULL(node)) {
+		dev_dbg(parent, "No reserved trace buffer specified\n");
+		return;
+	}
+
+	rc = of_address_to_resource(node, 0, &res);

This sequence is repeated again in the metadat area, where :

1. We get region by name.
2. Read the resource details.

Could we not make "the helper" do both and move the "of_node_put()"
inside the helper ?

Ack.

static int of_tmc_get_reserved_resource_by_name(struct device *dev,
					        const char *name,
					        struct resource *res)
{

 > +	int index, rc = -ENODEV;
 > +	struct device_node *node;

	if (!is_of_node(dev_fwnode(dev->fwnode)))
		return -ENODEV;
 > +
 > +	index = of_property_match_string(dev->of_node,
"memory-region-names", name);
 > +	if (index < 0)
 > +		return rc;
 > +
 > +	node = of_parse_phandle(node, "memory-region", index);
	if (!node)
		return rc;

	if (!of_address_to_resource(node, 0, res) &&
	    res->start != 0 && resource_size(res) != 0)
		rc = 0;
	of_node_put(node);

	return rc;
}

quoted

+	of_node_put(node);
+	if (rc || res.start == 0 || resource_size(&res) == 0) {
+		dev_err(parent, "Reserved trace buffer memory is

invalid\n");

quoted

+		return;
+	}

and the caller does :

	if (of_tmc_get_reserved_area_by_name(parent, "tracedata", &res))
		return;

Okay.

Ack.

quoted

  }

  static bool etr_can_use_flat_mode(struct etr_buf_hw *buf_hw, ssize_t
etr_buf_size) @@ -1830,6 +1903,7 @@ static const char *const

buf_modes_str[] = {

quoted

  	[ETR_MODE_FLAT]		= "flat",
  	[ETR_MODE_ETR_SG]	= "tmc-sg",
  	[ETR_MODE_CATU]		= "catu",
+	[ETR_MODE_RESRV]	= "resrv",
  	[ETR_MODE_AUTO]		= "auto",
  };

@@ -1848,6 +1922,9 @@ static ssize_t buf_modes_available_show(struct

device *dev,

quoted

  	if (buf_hw.has_catu)
  		size += sysfs_emit_at(buf, size, "%s ",
buf_modes_str[ETR_MODE_CATU]);

+	if (buf_hw.has_resrv)
+		size += sysfs_emit_at(buf, size, "%s ",
+buf_modes_str[ETR_MODE_RESRV]);
+
  	size += sysfs_emit_at(buf, size, "\n");
  	return size;
  }

@@ -1875,6 +1952,8 @@ static ssize_t buf_mode_preferred_store(struct

device *dev,

quoted

  		drvdata->etr_mode = ETR_MODE_ETR_SG;
  	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_CATU]) &&

buf_hw.has_catu)

quoted

  		drvdata->etr_mode = ETR_MODE_CATU;
+	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_RESRV]) &&

buf_hw.has_resrv)

quoted

+		drvdata->etr_mode = ETR_MODE_RESRV;
  	else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_AUTO]))
  		drvdata->etr_mode = ETR_MODE_AUTO;
  	else

diff --git a/drivers/hwtracing/coresight/coresight-tmc.h

b/drivers/hwtracing/coresight/coresight-tmc.h
index c77763b49de0..c23dc9917ab9 100644

--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h

@@ -135,6 +135,7 @@ enum etr_mode {
  	ETR_MODE_FLAT,		/* Uses contiguous flat buffer */
  	ETR_MODE_ETR_SG,	/* Uses in-built TMC ETR SG mechanism */
  	ETR_MODE_CATU,		/* Use SG mechanism in CATU */
+	ETR_MODE_RESRV,		/* Use reserved region contiguous

buffer */

quoted

  	ETR_MODE_AUTO,		/* Use the default mechanism */
  };

@@ -164,6 +165,17 @@ struct etr_buf {
  	void				*private;
  };

+/**
+ * @paddr	: Start address of reserved memory region.
+ * @vaddr	: Corresponding CPU virtual address.
+ * @size	: Size of reserved memory region.
+ */
+struct tmc_resrv_buf {
+	phys_addr_t     paddr;
+	void		*vaddr;
+	size_t		size;
+};
+
  /**
   * struct tmc_drvdata - specifics associated to an TMC component
   * @pclk:	APB clock if present, otherwise NULL

@@ -188,6 +200,10 @@ struct etr_buf {
   * @idr_mutex:	Access serialisation for idr.
   * @sysfs_buf:	SYSFS buffer for ETR.
   * @perf_buf:	PERF buffer for ETR.
+ * @crash_tbuf:	Used by ETR as hardware trace buffer and for trace

data

quoted

+ *		retention (after crash) only when ETR_MODE_RESRV buffer
+ *		mode is enabled. Used by ETF for trace data retention
+ *		(after crash) by default.

Minor nit: This need not be called crash_tbuf, could instead be resrv_buf as
we use it everywhere.

Ack.

Suzuki

quoted

   */
  struct tmc_drvdata {
  	struct clk		*pclk;

@@ -213,6 +229,7 @@ struct tmc_drvdata {
  	struct mutex		idr_mutex;
  	struct etr_buf		*sysfs_buf;
  	struct etr_buf		*perf_buf;
+	struct tmc_resrv_buf	crash_tbuf;
  };

  struct etr_buf_operations {

@@ -330,6 +347,16 @@ tmc_sg_table_buf_size(struct tmc_sg_table

*sg_table)

quoted

  	return (unsigned long)sg_table->data_pages.nr_pages <<

PAGE_SHIFT;

quoted

  }

+static inline bool is_tmc_reserved_region_valid(struct device *dev) {
+	struct tmc_drvdata *drvdata = dev_get_drvdata(dev);
+
+	if (drvdata->crash_tbuf.paddr &&
+		drvdata->crash_tbuf.size)
+		return true;
+	return false;
+}
+
  struct coresight_device *tmc_etr_get_catu_device(struct tmc_drvdata
*drvdata);

  void tmc_etr_set_catu_ops(const struct etr_buf_operations *catu);