[PATCH v5 0/2] Add support for UltraSoc System Memory Buffer

[PATCH v5 0/2] Add support for UltraSoc System Memory Buffer

[Qi Liu]

Add support for UltraSoc System Memory Buffer.

Change since v4:
- Add a simple document of SMB driver according to Suzuki's comment.
- Address the comments from Suzuki.
- https://lore.kernel.org/linux-arm-kernel/20220128061755.31909-1-liuqi115@huawei.com/

Change since v3:
- Modify the file header according to community specifications.
- Address the comments from Mathieu.
- Link:https://lore.kernel.org/linux-arm-kernel/20211118110016.40398-1-liuqi115@huawei.com/
Change since v2:
- Move ultrasoc driver to drivers/hwtracing/coresight.
- Link:https://lists.linaro.org/pipermail/coresight/2021-November/007310.html

Change since v1:
- Drop the document of UltraSoc according to Mathieu's comment.
- Add comments to explain some private hardware settings.
- Address the comments from Mathieu.
- Link: https://lists.linaro.org/pipermail/coresight/2021-August/006842.html

Change since RFC:
- Move driver to drivers/hwtracing/coresight/ultrasoc.
- Remove ultrasoc-axi-com.c, as AXI-COM doesn't need to be configured in
  basic tracing function.
- Remove ultrasoc.c as SMB does not need to register with the ultrasoc core.
- Address the comments from Mathieu and Suzuki.
- Link: https://lists.linaro.org/pipermail/coresight/2021-June/006535.html

Qi Liu (2):
  drivers/coresight: Add UltraSoc System Memory Buffer driver
  Documentation: Add document for UltraSoc SMB drivers

 .../trace/coresight/ultrasoc-smb.rst          |  79 +++
 drivers/hwtracing/coresight/Kconfig           |  10 +
 drivers/hwtracing/coresight/Makefile          |   1 +
 drivers/hwtracing/coresight/ultrasoc-smb.c    | 643 ++++++++++++++++++
 drivers/hwtracing/coresight/ultrasoc-smb.h    | 106 +++
 5 files changed, 839 insertions(+)
 create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst
 create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
 create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h

-- 
2.24.0

[PATCH v5 1/2] drivers/coresight: Add UltraSoc System Memory Buffer driver

[Qi Liu]

This patch adds driver for UltraSoc SMB(System Memory Buffer)
device. SMB provides a way to buffer messages from ETM, and
store these CPU instructions in system memory.

SMB is developed by UltraSoc technology, which is acquired by
Siemens, and we still use "UltraSoc" to name driver.

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Tested-by: JunHao He <hejunhao2@hisilicon.com>
---
 drivers/hwtracing/coresight/Kconfig        |  10 +
 drivers/hwtracing/coresight/Makefile       |   1 +
 drivers/hwtracing/coresight/ultrasoc-smb.c | 643 +++++++++++++++++++++
 drivers/hwtracing/coresight/ultrasoc-smb.h | 106 ++++
 4 files changed, 760 insertions(+)
 create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
 create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index 514a9b8086e3..4380eb1a0a73 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -201,4 +201,14 @@ config CORESIGHT_TRBE
 
 	  To compile this driver as a module, choose M here: the module will be
 	  called coresight-trbe.
+config ULTRASOC_SMB
+	tristate "Ultrasoc system memory buffer drivers"
+	depends on ACPI && ARM64 && CORESIGHT_LINKS_AND_SINKS
+	help
+	  This driver provides support for the Ultrasoc system memory buffer (SMB).
+	  SMB is responsible for receiving the trace data from Coresight ETM devices
+	  and storing them to a system buffer.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ultrasoc-smb.
 endif
diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
index b6c4a48140ec..344dba8d6ff8 100644
--- a/drivers/hwtracing/coresight/Makefile
+++ b/drivers/hwtracing/coresight/Makefile
@@ -27,3 +27,4 @@ obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o
 obj-$(CONFIG_CORESIGHT_TRBE) += coresight-trbe.o
 coresight-cti-y := coresight-cti-core.o	coresight-cti-platform.o \
 		   coresight-cti-sysfs.o
+obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
new file mode 100644
index 000000000000..9a93b7fc7bda
--- /dev/null
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -0,0 +1,643 @@
+// SPDX-License-Identifier: MIT/GPL
+/*
+ * Siemens System Memory Buffer driver.
+ * Copyright(c) 2021, HiSilicon Limited.
+ */
+
+#include <linux/acpi.h>
+#include <linux/circ_buf.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+
+#include "ultrasoc-smb.h"
+
+DEFINE_CORESIGHT_DEVLIST(sink_devs, "ultra_smb");
+
+#define ULTRASOC_SMB_DSM_UUID	"82ae1283-7f6a-4cbe-aa06-53e8fb24db18"
+
+static bool smb_buffer_is_empty(struct smb_drv_data *drvdata)
+{
+	u32 buf_status = readl(drvdata->base + SMB_LB_INT_STS);
+
+	return buf_status & BIT(0) ? false : true;
+}
+
+static bool smb_buffer_cmp_pointer(struct smb_drv_data *drvdata)
+{
+	u32 wr_offset, rd_offset;
+
+	wr_offset = readl(drvdata->base + SMB_LB_WR_ADDR);
+	rd_offset = readl(drvdata->base + SMB_LB_RD_ADDR);
+	return wr_offset == rd_offset;
+}
+
+static void smb_reset_buffer_status(struct smb_drv_data *drvdata)
+{
+	writel(0xf, drvdata->base + SMB_LB_INT_STS);
+}
+
+/* Purge data remaining in hardware path in case them influence next trace */
+static void smb_purge_data(struct smb_drv_data *drvdata)
+{
+	writel(0x1, drvdata->base + SMB_LB_PURGE);
+}
+
+static void smb_update_data_size(struct smb_drv_data *drvdata)
+{
+	struct smb_data_buffer *sdb = &drvdata->sdb;
+	u32 write_offset;
+
+	smb_purge_data(drvdata);
+	if (smb_buffer_cmp_pointer(drvdata)) {
+		if (smb_buffer_is_empty(drvdata))
+			sdb->data_size = 0;
+		else
+			sdb->data_size = sdb->buf_size;
+		return;
+	}
+
+	write_offset = readl(drvdata->base + SMB_LB_WR_ADDR) - sdb->start_addr;
+	sdb->data_size = CIRC_CNT(write_offset, sdb->rd_offset, sdb->buf_size);
+}
+
+static int smb_open(struct inode *inode, struct file *file)
+{
+	struct smb_drv_data *drvdata = container_of(file->private_data,
+					struct smb_drv_data, miscdev);
+
+	if (local_cmpxchg(&drvdata->reading, 0, 1))
+		return -EBUSY;
+
+	return 0;
+}
+
+static ssize_t smb_read(struct file *file, char __user *data, size_t len,
+			loff_t *ppos)
+{
+	struct smb_drv_data *drvdata = container_of(file->private_data,
+						struct smb_drv_data, miscdev);
+	struct smb_data_buffer *sdb = &drvdata->sdb;
+	struct device *dev = &drvdata->csdev->dev;
+	unsigned long flags;
+	int to_copy = 0;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	if (atomic_read(drvdata->csdev->refcnt)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
+	if (!sdb->data_size) {
+		smb_update_data_size(drvdata);
+		if (!sdb->data_size)
+			goto out;
+	}
+
+	to_copy = min(sdb->data_size, len);
+
+	/* Copy parts of trace data when read pointer wrap around SMB buffer */
+	if (sdb->rd_offset + to_copy > sdb->buf_size)
+		to_copy = sdb->buf_size - sdb->rd_offset;
+
+	if (copy_to_user(data, (void *)sdb->buf_base + sdb->rd_offset,
+			 to_copy)) {
+		dev_dbg(dev, "Failed to copy data to user.\n");
+		to_copy = -EFAULT;
+		goto out;
+	}
+
+	*ppos += to_copy;
+	sdb->data_size -= to_copy;
+	sdb->rd_offset += to_copy;
+	sdb->rd_offset %= sdb->buf_size;
+	writel(sdb->start_addr + sdb->rd_offset,
+	       drvdata->base + SMB_LB_RD_ADDR);
+	dev_dbg(dev, "%d bytes copied.\n", to_copy);
+out:
+	if (!sdb->data_size)
+		smb_reset_buffer_status(drvdata);
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	return to_copy;
+}
+
+static int smb_release(struct inode *inode, struct file *file)
+{
+	struct smb_drv_data *drvdata = container_of(file->private_data,
+						struct smb_drv_data, miscdev);
+	local_set(&drvdata->reading, 0);
+	return 0;
+}
+
+static const struct file_operations smb_fops = {
+	.owner		= THIS_MODULE,
+	.open		= smb_open,
+	.read		= smb_read,
+	.release	= smb_release,
+	.llseek		= no_llseek,
+};
+
+smb_reg(read_pos, SMB_LB_RD_ADDR);
+smb_reg(write_pos, SMB_LB_WR_ADDR);
+smb_reg(buf_status, SMB_LB_INT_STS);
+
+static ssize_t buf_size_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(dev->parent);
+
+	return sysfs_emit(buf, "0x%lx\n", drvdata->sdb.buf_size);
+}
+static DEVICE_ATTR_RO(buf_size);
+
+static struct attribute *smb_sink_attrs[] = {
+	&dev_attr_read_pos.attr,
+	&dev_attr_write_pos.attr,
+	&dev_attr_buf_status.attr,
+	&dev_attr_buf_size.attr,
+	NULL,
+};
+
+static const struct attribute_group smb_sink_group = {
+	.attrs = smb_sink_attrs,
+	.name = "mgmt",
+};
+
+static const struct attribute_group *smb_sink_groups[] = {
+	&smb_sink_group,
+	NULL,
+};
+
+static int smb_set_perf_buffer(struct perf_output_handle *handle)
+{
+	struct cs_buffers *buf = etm_perf_sink_config(handle);
+	u32 head;
+
+	if (!buf)
+		return -EINVAL;
+
+	/* Wrap head around to the amount of space we have */
+	head = handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1);
+
+	/* Find the page to write to and offset within that page */
+	buf->cur = head / PAGE_SIZE;
+	buf->offset = head % PAGE_SIZE;
+
+	local_set(&buf->data_size, 0);
+
+	return 0;
+}
+
+static void smb_enable_hw(struct smb_drv_data *drvdata)
+{
+	writel(0x1, drvdata->base + SMB_GLOBAL_EN);
+}
+
+static void smb_disable_hw(struct smb_drv_data *drvdata)
+{
+	writel(0x0, drvdata->base + SMB_GLOBAL_EN);
+}
+
+static int smb_enable_sysfs(struct coresight_device *csdev)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	if (drvdata->mode == CS_MODE_PERF) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (drvdata->mode == CS_MODE_DISABLED) {
+		smb_enable_hw(drvdata);
+		drvdata->mode = CS_MODE_SYSFS;
+	}
+
+	atomic_inc(csdev->refcnt);
+out:
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	return ret;
+}
+
+static int smb_enable_perf(struct coresight_device *csdev, void *data)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct device *dev = &drvdata->csdev->dev;
+	struct perf_output_handle *handle = data;
+	struct cs_buffers *buf = etm_perf_sink_config(handle);
+	unsigned long flags;
+	int ret = 0;
+	pid_t pid;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	if (drvdata->mode == CS_MODE_SYSFS) {
+		dev_dbg(dev, "Device is already in used by sysfs.\n");
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* Get a handle on the pid of the target process */
+	pid = buf->pid;
+	if (drvdata->pid != -1 && drvdata->pid != pid) {
+		dev_dbg(dev, "Device is already in used by other session.\n");
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* The sink is already enabled by this session */
+	if (drvdata->pid == pid) {
+		atomic_inc(csdev->refcnt);
+		goto out;
+	}
+
+	ret = smb_set_perf_buffer(handle);
+	if (ret)
+		goto out;
+
+	smb_enable_hw(drvdata);
+	drvdata->pid = pid;
+	drvdata->mode = CS_MODE_PERF;
+	atomic_inc(csdev->refcnt);
+out:
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	return ret;
+}
+
+static int smb_enable(struct coresight_device *csdev, u32 mode, void *data)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
+	int ret;
+
+	/* Do nothing if trace data is reading by other interface now */
+	if (local_read(&drvdata->reading))
+		return -EBUSY;
+
+	switch (mode) {
+	case CS_MODE_SYSFS:
+		ret = smb_enable_sysfs(csdev);
+		break;
+	case CS_MODE_PERF:
+		ret = smb_enable_perf(csdev, data);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	if (ret)
+		return ret;
+	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled.\n");
+
+	return 0;
+}
+
+static int smb_disable(struct coresight_device *csdev)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
+	unsigned long flags;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	if (local_read(&drvdata->reading)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
+	if (atomic_dec_return(csdev->refcnt)) {
+		spin_unlock_irqrestore(&drvdata->spinlock, flags);
+		return -EBUSY;
+	}
+
+	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
+	smb_disable_hw(drvdata);
+	smb_purge_data(drvdata);
+
+	/*
+	 * In perf mode, sink->disable is called after sink->update_buffer, so
+	 * need to synchronize the read pointer to write pointer, to make sure
+	 * these purged data won't influence next trace.
+	 */
+	if (drvdata->mode == CS_MODE_PERF)
+		writel(readl(drvdata->base + SMB_LB_WR_ADDR),
+		       drvdata->base + SMB_LB_RD_ADDR);
+
+	/* Dissociate from the target process. */
+	drvdata->pid = -1;
+	drvdata->mode = CS_MODE_DISABLED;
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+
+	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled.\n");
+	return 0;
+}
+
+static void *smb_alloc_buffer(struct coresight_device *csdev,
+			      struct perf_event *event, void **pages,
+			      int nr_pages, bool overwrite)
+{
+	struct cs_buffers *buf;
+	int node;
+
+	node = (event->cpu == -1) ? NUMA_NO_NODE : cpu_to_node(event->cpu);
+	buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);
+	if (!buf)
+		return NULL;
+
+	buf->snapshot = overwrite;
+	buf->nr_pages = nr_pages;
+	buf->data_pages = pages;
+	buf->pid = task_pid_nr(event->owner);
+
+	return buf;
+}
+
+static void smb_free_buffer(void *config)
+{
+	struct cs_buffers *buf = config;
+
+	kfree(buf);
+}
+
+static void smb_sync_perf_buffer(struct smb_drv_data *drvdata,
+				 struct cs_buffers *buf,
+				 unsigned long data_size)
+{
+	struct smb_data_buffer *sdb = &drvdata->sdb;
+	char **dst_pages = (char **)buf->data_pages;
+	unsigned long page_offset = buf->offset;
+	unsigned int cur = buf->cur;
+	unsigned long to_copy;
+
+	while (data_size) {
+		unsigned long page_space = PAGE_SIZE - page_offset;
+
+		/* Copy parts of trace data when read pointer wrap around */
+		if (sdb->rd_offset + page_space > sdb->buf_size)
+			to_copy = sdb->buf_size - sdb->rd_offset;
+		else
+			to_copy = min(data_size, page_space);
+
+		memcpy_fromio(dst_pages[cur] + page_offset,
+			      sdb->buf_base + sdb->rd_offset, to_copy);
+
+		page_offset += to_copy;
+		if (page_offset >= PAGE_SIZE) {
+			page_offset = 0;
+			cur++;
+			cur %= buf->nr_pages;
+		}
+		data_size -= to_copy;
+		sdb->rd_offset += to_copy;
+		sdb->rd_offset %= sdb->buf_size;
+	}
+
+	sdb->data_size = 0;
+	writel(sdb->start_addr + sdb->rd_offset,
+	       drvdata->base + SMB_LB_RD_ADDR);
+	smb_reset_buffer_status(drvdata);
+}
+
+static unsigned long smb_update_buffer(struct coresight_device *csdev,
+				       struct perf_output_handle *handle,
+				       void *sink_config)
+{
+	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct smb_data_buffer *sdb = &drvdata->sdb;
+	struct cs_buffers *buf = sink_config;
+	unsigned long data_size = 0;
+	unsigned long flags;
+	bool lost = false;
+
+	if (!buf)
+		return 0;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	/* Don't do anything if another tracer is using this sink. */
+	if (atomic_read(csdev->refcnt) != 1)
+		goto out;
+
+	smb_update_data_size(drvdata);
+	data_size = sdb->data_size;
+
+	/*
+	 * The SMB buffer may be bigger than the space available in the
+	 * perf ring buffer (handle->size). If so advance the offset so
+	 * that we get the latest trace data.
+	 */
+	if (data_size > handle->size) {
+		sdb->rd_offset += data_size - handle->size;
+		sdb->rd_offset %= sdb->buf_size;
+		data_size = handle->size;
+		lost = true;
+	}
+
+	smb_sync_perf_buffer(drvdata, buf, data_size);
+	if (!buf->snapshot && lost)
+		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
+
+out:
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+	return data_size;
+}
+
+static const struct coresight_ops_sink smb_cs_ops = {
+	.enable		= smb_enable,
+	.disable	= smb_disable,
+	.alloc_buffer	= smb_alloc_buffer,
+	.free_buffer	= smb_free_buffer,
+	.update_buffer	= smb_update_buffer,
+};
+
+static const struct coresight_ops cs_ops = {
+	.sink_ops	= &smb_cs_ops,
+};
+
+static int smb_init_data_buffer(struct platform_device *pdev,
+				struct smb_data_buffer *sdb)
+{
+	struct resource *res;
+	void __iomem *base;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (IS_ERR(res)) {
+		dev_err(&pdev->dev, "SMB device failed to get resource.\n");
+		return -EINVAL;
+	}
+
+	sdb->start_addr = res->start & SMB_BASE_LOW_MASK;
+	sdb->buf_size = resource_size(res);
+	if (sdb->buf_size == 0)
+		return -EINVAL;
+
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	sdb->buf_base = base;
+
+	return 0;
+}
+
+static void smb_init_hw(struct smb_drv_data *drvdata)
+{
+	/* First disable smb and clear the status of SMB buffer */
+	smb_reset_buffer_status(drvdata);
+	smb_disable_hw(drvdata);
+	smb_purge_data(drvdata);
+
+	writel(SMB_BUF_CFG_STREAMING, drvdata->base + SMB_LB_CFG_LO);
+	writel(SMB_MSG_FILTER, drvdata->base + SMB_LB_CFG_HI);
+	writel(SMB_GLOBAL_CFG, drvdata->base + SMB_CFG_REG);
+	writel(SMB_GLB_INT_CFG, drvdata->base + SMB_GLOBAL_INT);
+	writel(SMB_BUF_INT_CFG, drvdata->base + SMB_LB_INT_CTRL);
+}
+
+static int smb_register_sink(struct platform_device *pdev,
+			     struct smb_drv_data *drvdata)
+{
+	struct coresight_platform_data *pdata = NULL;
+	struct coresight_desc desc = { 0 };
+	int ret;
+
+	pdata = coresight_get_platform_data(&pdev->dev);
+	if (IS_ERR(pdata))
+		return PTR_ERR(pdata);
+
+	desc.type = CORESIGHT_DEV_TYPE_SINK;
+	desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
+	desc.ops = &cs_ops;
+	desc.pdata = pdata;
+	desc.dev = &pdev->dev;
+	desc.groups = smb_sink_groups;
+	desc.name = coresight_alloc_device_name(&sink_devs, &pdev->dev);
+	if (!desc.name) {
+		dev_err(&pdev->dev, "Failed to alloc coresight device name.");
+		return -ENOMEM;
+	}
+
+	drvdata->csdev = coresight_register(&desc);
+	if (IS_ERR(drvdata->csdev))
+		return PTR_ERR(drvdata->csdev);
+
+	drvdata->miscdev.name = desc.name;
+	drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;
+	drvdata->miscdev.fops = &smb_fops;
+	ret = misc_register(&drvdata->miscdev);
+	if (ret) {
+		coresight_unregister(drvdata->csdev);
+		dev_err(&pdev->dev, "Failed to register misc, ret=%d.\n", ret);
+	}
+
+	return ret;
+}
+
+static void smb_unregister_sink(struct smb_drv_data *drvdata)
+{
+	misc_deregister(&drvdata->miscdev);
+	coresight_unregister(drvdata->csdev);
+}
+
+static int smb_config_inport(struct device *dev, bool enable)
+{
+	u64 func = enable ? 1 : 0;
+	union acpi_object *obj;
+	guid_t guid;
+	u64 rev = 0;
+
+	/*
+	 * Using DSM calls to enable/disable ultrasoc hardwares on
+	 * tracing path, to prevent ultrasoc packet format being exposed.
+	 */
+	if (guid_parse(ULTRASOC_SMB_DSM_UUID, &guid)) {
+		dev_err(dev, "Get GUID failed.\n");
+		return -EINVAL;
+	}
+
+	obj = acpi_evaluate_dsm(ACPI_HANDLE(dev), &guid, rev, func, NULL);
+	if (!obj)
+		dev_err(dev, "ACPI handle failed!\n");
+	else
+		ACPI_FREE(obj);
+
+	return 0;
+}
+
+static int smb_probe(struct platform_device *pdev)
+{
+	struct smb_drv_data *drvdata;
+	int ret;
+
+	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	drvdata->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(drvdata->base)) {
+		dev_err(&pdev->dev, "Failed to ioremap resource.\n");
+		return PTR_ERR(drvdata->base);
+	}
+
+	ret = smb_init_data_buffer(pdev, &drvdata->sdb);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to init buffer, ret = %d.\n", ret);
+		return ret;
+	}
+
+	smb_init_hw(drvdata);
+	spin_lock_init(&drvdata->spinlock);
+	drvdata->pid = -1;
+
+	ret = smb_register_sink(pdev, drvdata);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register smb sink.\n");
+		return ret;
+	}
+
+	ret = smb_config_inport(&pdev->dev, true);
+	if (ret) {
+		smb_unregister_sink(drvdata);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, drvdata);
+	return 0;
+}
+
+static int smb_remove(struct platform_device *pdev)
+{
+	struct smb_drv_data *drvdata = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = smb_config_inport(&pdev->dev, false);
+	if (ret)
+		return ret;
+
+	smb_unregister_sink(drvdata);
+	return 0;
+}
+
+static const struct acpi_device_id ultrasoc_smb_acpi_match[] = {
+	{"HISI03A1", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, ultrasoc_smb_acpi_match);
+
+static struct platform_driver smb_driver = {
+	.driver = {
+		.name = "ultrasoc-smb",
+		.acpi_match_table = ACPI_PTR(ultrasoc_smb_acpi_match),
+		.suppress_bind_attrs = true,
+	},
+	.probe = smb_probe,
+	.remove = smb_remove,
+};
+module_platform_driver(smb_driver);
+
+MODULE_DESCRIPTION("UltraSoc smb driver");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Jonathan Zhou <jonathan.zhouwen@huawei.com>");
+MODULE_AUTHOR("Qi Liu <liuqi115@huawei.com>");
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
new file mode 100644
index 000000000000..56c6bdd2f35b
--- /dev/null
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Siemens System Memory Buffer driver.
+ * Copyright(c) 2021, HiSilicon Limited.
+ */
+
+#ifndef _ULTRASOC_SMB_H
+#define _ULTRASOC_SMB_H
+
+#include <linux/coresight.h>
+#include <linux/list.h>
+#include <linux/miscdevice.h>
+
+#include "coresight-etm-perf.h"
+#include "coresight-priv.h"
+
+/* Offset of SMB logical buffer registers */
+#define SMB_CFG_REG		0x00
+#define SMB_GLOBAL_EN		0x04
+#define SMB_GLOBAL_INT		0x08
+#define SMB_LB_CFG_LO		0x40
+#define SMB_LB_CFG_HI		0x44
+#define SMB_LB_INT_CTRL		0x48
+#define SMB_LB_INT_STS		0x4c
+#define SMB_LB_LIMIT		0x58
+#define SMB_LB_RD_ADDR		0x5c
+#define SMB_LB_WR_ADDR		0x60
+#define SMB_LB_PURGE		0x64
+
+/* Set SMB_CFG_REG register */
+#define SMB_BURST_LEN		GENMASK(7, 4)
+#define SMB_IDLE_PRD		GENMASK(15, 12)
+#define SMB_MEM_WR		GENMASK(17, 16)
+#define SMB_MEM_RD		(GENMASK(26, 25) | GENMASK(23, 22))
+#define SMB_GLOBAL_CFG		(SMB_IDLE_PRD |	SMB_MEM_WR | SMB_MEM_RD | \
+				 SMB_BURST_LEN)
+
+/* Set SMB_GLOBAL_INT register */
+#define SMB_INT_EN		BIT(0)
+#define SMB_INT_TYPE_PULSE	BIT(1)
+#define SMB_INT_POLARITY_HIGH	BIT(2)
+#define SMB_GLB_INT_CFG		(SMB_INT_EN | SMB_INT_TYPE_PULSE |	\
+				 SMB_INT_POLARITY_HIGH)
+
+/* Set SMB_LB_CFG_LO register */
+#define SMB_BUF_EN		BIT(0)
+#define SMB_BUF_SINGLE_END	BIT(1)
+#define SMB_BUF_INIT		BIT(8)
+#define SMB_BUF_CONTINUOUS	BIT(11)
+#define SMB_FLOW_MASK		GENMASK(19, 16)
+#define SMB_BUF_CFG_STREAMING	(SMB_BUF_INIT | SMB_BUF_CONTINUOUS |	\
+				 SMB_FLOW_MASK | SMB_BUF_SINGLE_END |	\
+				 SMB_BUF_EN)
+
+#define SMB_BASE_LOW_MASK	GENMASK(31, 0)
+
+/* Set SMB_LB_CFG_HI register */
+#define SMB_MSG_FILTER		GENMASK(15, 8)
+
+/* Set SMB_LB_INT_CTRL */
+#define SMB_BUF_INT_EN		BIT(0)
+#define SMB_BUF_NOTE_MASK	GENMASK(11, 8)
+#define SMB_BUF_INT_CFG		(SMB_BUF_INT_EN | SMB_BUF_NOTE_MASK)
+
+/**
+ * struct smb_data_buffer - Details of the buffer used by SMB
+ * @buf_base	: Memory mapped base address of SMB.
+ * @start_addr	: SMB buffer start Physical address.
+ * @buf_size	: Size of the buffer.
+ * @data_size	: Size of Trace data copy to userspace.
+ * @rd_offset	: Offset of the read pointer in the buffer.
+ */
+struct smb_data_buffer {
+	void __iomem *buf_base;
+	u32 start_addr;
+	unsigned long buf_size;
+	unsigned long data_size;
+	unsigned long rd_offset;
+};
+
+/**
+ * struct smb_drv_data - specifics associated to an SMB component
+ * @base:	Memory mapped base address for SMB component.
+ * @csdev:	Component vitals needed by the framework.
+ * @sdb:	Data buffer for SMB.
+ * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
+ * @spinlock:	Only one at a time pls.
+ * @reading:	Synchronise user space access to SMB buffer.
+ * @pid:	Process ID of the process being monitored by the session
+ *		that is using this component.
+ * @mode:	how this SMB is being used, perf mode or sysfs mode.
+ */
+struct smb_drv_data {
+	void __iomem *base;
+	struct coresight_device	*csdev;
+	struct smb_data_buffer sdb;
+	struct miscdevice miscdev;
+	spinlock_t spinlock;
+	local_t reading;
+	pid_t pid;
+	u32 mode;
+};
+
+#define smb_reg(name, offset)  coresight_simple_reg32(struct smb_drv_data, name, offset)
+
+#endif
-- 
2.24.0

[PATCH v5 2/2] Documentation: Add document for UltraSoc SMB drivers

[Qi Liu]

This patch bring in a documentation for UltraSoc SMB drivers.
It simple descripts the device, sysfs interface and the
firmware bindings.

Signed-off-by: Qi Liu <liuqi115@huawei.com>
---
 .../trace/coresight/ultrasoc-smb.rst          | 79 +++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst

diff --git a/Documentation/trace/coresight/ultrasoc-smb.rst b/Documentation/trace/coresight/ultrasoc-smb.rst
new file mode 100644
index 000000000000..024fa4492f42
--- /dev/null
+++ b/Documentation/trace/coresight/ultrasoc-smb.rst
@@ -0,0 +1,79 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+UltraSoc - HW Assisted Tracing on SoC
+======================================
+   :Author:   Qi Liu <liuqi115@huawei.com>
+   :Date:     March 2022
+
+Introduction
+------------
+
+UltraSoc SMB is a per SCCL hardware, and it provides a way to buffer and store
+CPU trace messages in a region of shared system memory. SMB is plugged as
+a coresight sink device and the corresponding trace generators (ETM) are
+plugged in as source devices.
+
+Sysfs files and directories
+---------------------------
+
+The SMB devices appear on the existing coresight bus alongside the other
+coresight devices::
+
+	$# ls /sys/bus/coresight/devices/
+	ultra_smb0   ultra_smb1   ultra_smb2   ultra_smb3
+
+The ``ultra_smb<N>`` named SMB associated with SCCL.::
+
+	$# ls /sys/bus/coresight/devices/ultra_smb0
+	enable_sink   mgmt
+	$# ls /sys/bus/coresight/devices/ultra_smb0/mgmt
+	buf_size  buf_status  read_pos  write_pos
+
+*Key file items are:-*
+   * ``read_pos``: Shows the value held by UltraSoc SMB Read Pointer register.
+   * ``write_pos``: Shows the value held by UltraSoc SMB Write Pointer register.
+   * ``buf_status``: Shows the value held by UltraSoc SMB status register.
+		     BIT(0) is zero means buffer is empty.
+   * ``buf_size``: Shows the buffer size of each UltraSoc SMB device.
+
+Firmware Bindings
+---------------------------
+
+Firmware binding of SMB device describes SMB device indentifier, resource
+information and graph structure.
+
+SMB is platform device and device id is "HISI03A1", resource of device is
+declared using the _CRS method. Each SMB must present two base address,
+the first one is the configuration base address of SMB device, the second
+one is the base address of shared system memory.
+
+examples::
+
+    Device(USMB) {                                               \
+      Name(_HID, "HISI03A1")                                     \
+      Name(_CRS, ResourceTemplate() {                            \
+          MEM_RESRC(0x95100000, 0x951FFFFF, 0x100000)            \
+          MEM_RESRC(0x50000000, 0x53FFFFFF, 0x4000000)           \
+      })                                                         \
+      Name(_DSD, Package() {                                     \
+        ToUUID("ab02a46b-74c7-45a2-bd68-f7d344ef2153"),          \
+        Package() {                                              \
+          0,                                                     \
+          1,                                                     \
+          Package() {                                            \
+            1,                                                   \
+            ToUUID("3ecbc8b6-1d0e-4fb3-8107-e627f805c6cd"),      \
+            8,                                                   \
+            Package() {0x8, 0, \_SB.S00.SL11.CL28.F008, 0},       \
+            Package() {0x9, 0, \_SB.S00.SL11.CL29.F009, 0},       \
+            Package() {0xa, 0, \_SB.S00.SL11.CL2A.F010, 0},       \
+            Package() {0xb, 0, \_SB.S00.SL11.CL2B.F011, 0},       \
+            Package() {0xc, 0, \_SB.S00.SL11.CL2C.F012, 0},       \
+            Package() {0xd, 0, \_SB.S00.SL11.CL2D.F013, 0},       \
+            Package() {0xe, 0, \_SB.S00.SL11.CL2E.F014, 0},       \
+            Package() {0xf, 0, \_SB.S00.SL11.CL2F.F015, 0},       \
+          }                                                      \
+        }                                                        \
+      })                                                         \
+    }
-- 
2.24.0

Re: [PATCH v5 0/2] Add support for UltraSoc System Memory Buffer

[liuqi (BA)]

Gentle ping. Any comment or suggestion is appreciated.

Thanks,
Qi

On 2022/4/16 16:39, Qi Liu wrote:
> Add support for UltraSoc System Memory Buffer.
> 
> Change since v4:
> - Add a simple document of SMB driver according to Suzuki's comment.
> - Address the comments from Suzuki.
> - https://lore.kernel.org/linux-arm-kernel/20220128061755.31909-1-liuqi115@huawei.com/
> 
> Change since v3:
> - Modify the file header according to community specifications.
> - Address the comments from Mathieu.
> - Link:https://lore.kernel.org/linux-arm-kernel/20211118110016.40398-1-liuqi115@huawei.com/
> Change since v2:
> - Move ultrasoc driver to drivers/hwtracing/coresight.
> - Link:https://lists.linaro.org/pipermail/coresight/2021-November/007310.html
> 
> Change since v1:
> - Drop the document of UltraSoc according to Mathieu's comment.
> - Add comments to explain some private hardware settings.
> - Address the comments from Mathieu.
> - Link: https://lists.linaro.org/pipermail/coresight/2021-August/006842.html
> 
> Change since RFC:
> - Move driver to drivers/hwtracing/coresight/ultrasoc.
> - Remove ultrasoc-axi-com.c, as AXI-COM doesn't need to be configured in
>    basic tracing function.
> - Remove ultrasoc.c as SMB does not need to register with the ultrasoc core.
> - Address the comments from Mathieu and Suzuki.
> - Link: https://lists.linaro.org/pipermail/coresight/2021-June/006535.html
> 
> Qi Liu (2):
>    drivers/coresight: Add UltraSoc System Memory Buffer driver
>    Documentation: Add document for UltraSoc SMB drivers
> 
>   .../trace/coresight/ultrasoc-smb.rst          |  79 +++
>   drivers/hwtracing/coresight/Kconfig           |  10 +
>   drivers/hwtracing/coresight/Makefile          |   1 +
>   drivers/hwtracing/coresight/ultrasoc-smb.c    | 643 ++++++++++++++++++
>   drivers/hwtracing/coresight/ultrasoc-smb.h    | 106 +++
>   5 files changed, 839 insertions(+)
>   create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst
>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h
> 

Re: [PATCH v5 2/2] Documentation: Add document for UltraSoc SMB drivers

[Suzuki K Poulose]

On 16/04/2022 09:39, Qi Liu wrote:
> This patch bring in a documentation for UltraSoc SMB drivers.
> It simple descripts the device, sysfs interface and the
> firmware bindings.
> 
> Signed-off-by: Qi Liu <liuqi115@huawei.com>
> ---
>   .../trace/coresight/ultrasoc-smb.rst          | 79 +++++++++++++++++++
>   1 file changed, 79 insertions(+)
>   create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst
> 
> diff --git a/Documentation/trace/coresight/ultrasoc-smb.rst b/Documentation/trace/coresight/ultrasoc-smb.rst
> new file mode 100644
> index 000000000000..024fa4492f42
> --- /dev/null
> +++ b/Documentation/trace/coresight/ultrasoc-smb.rst
> @@ -0,0 +1,79 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +======================================
> +UltraSoc - HW Assisted Tracing on SoC
> +======================================
> +   :Author:   Qi Liu <liuqi115@huawei.com>
> +   :Date:     March 2022
> +
> +Introduction
> +------------
> +
> +UltraSoc SMB is a per SCCL hardware, and it provides a way to buffer and store

nit: what is SCCL ?

> +CPU trace messages in a region of shared system memory. SMB is plugged as
> +a coresight sink device and the corresponding trace generators (ETM) are
> +plugged in as source devices.
> +
> +Sysfs files and directories
> +---------------------------
> +
> +The SMB devices appear on the existing coresight bus alongside the other
> +coresight devices::
> +
> +	$# ls /sys/bus/coresight/devices/
> +	ultra_smb0   ultra_smb1   ultra_smb2   ultra_smb3
> +
> +The ``ultra_smb<N>`` named SMB associated with SCCL.::
> +
> +	$# ls /sys/bus/coresight/devices/ultra_smb0
> +	enable_sink   mgmt
> +	$# ls /sys/bus/coresight/devices/ultra_smb0/mgmt
> +	buf_size  buf_status  read_pos  write_pos
> +
> +*Key file items are:-*
> +   * ``read_pos``: Shows the value held by UltraSoc SMB Read Pointer register.
> +   * ``write_pos``: Shows the value held by UltraSoc SMB Write Pointer register.
> +   * ``buf_status``: Shows the value held by UltraSoc SMB status register.
> +		     BIT(0) is zero means buffer is empty.
> +   * ``buf_size``: Shows the buffer size of each UltraSoc SMB device.
> +
> +Firmware Bindings
> +---------------------------
> +
> +Firmware binding of SMB device describes SMB device indentifier, resource
> +information and graph structure.
> +
> +SMB is platform device and device id is "HISI03A1", resource of device is
> +declared using the _CRS method. Each SMB must present two base address,
> +the first one is the configuration base address of SMB device, the second
> +one is the base address of shared system memory.
> +
> +examples::
> +
> +    Device(USMB) {                                               \
> +      Name(_HID, "HISI03A1")                                     \
> +      Name(_CRS, ResourceTemplate() {                            \
> +          MEM_RESRC(0x95100000, 0x951FFFFF, 0x100000)            \
> +          MEM_RESRC(0x50000000, 0x53FFFFFF, 0x4000000)           \
> +      })                                                         \


> +      Name(_DSD, Package() {                                     \
> +        ToUUID("ab02a46b-74c7-45a2-bd68-f7d344ef2153"),          \

nit: May be add a comment here to explain, use Arm CoreSight Graph
ACPI bindings to describe the connections.

> +        Package() {                                              \
> +          0,                                                     \
> +          1,                                                     \
> +          Package() {                                            \
> +            1,                                                   \
> +            ToUUID("3ecbc8b6-1d0e-4fb3-8107-e627f805c6cd"),      \
> +            8,                                                   \
> +            Package() {0x8, 0, \_SB.S00.SL11.CL28.F008, 0},       \
> +            Package() {0x9, 0, \_SB.S00.SL11.CL29.F009, 0},       \
> +            Package() {0xa, 0, \_SB.S00.SL11.CL2A.F010, 0},       \
> +            Package() {0xb, 0, \_SB.S00.SL11.CL2B.F011, 0},       \
> +            Package() {0xc, 0, \_SB.S00.SL11.CL2C.F012, 0},       \
> +            Package() {0xd, 0, \_SB.S00.SL11.CL2D.F013, 0},       \
> +            Package() {0xe, 0, \_SB.S00.SL11.CL2E.F014, 0},       \
> +            Package() {0xf, 0, \_SB.S00.SL11.CL2F.F015, 0},       \
> +          }                                                      \

Interesting, are there multiple input ports for the SMB ? We haven't
seen an instance of a "sink" that supports this. So, would be
interesting to see how the driver copes with that scenario.

Suzuki



> +        }                                                        \
> +      })                                                         \
> +    }

Re: [PATCH v5 1/2] drivers/coresight: Add UltraSoc System Memory Buffer driver

[Suzuki K Poulose]

Hi Qi Liu

Apologies for the delay. I have some more comments below.

On 16/04/2022 09:39, Qi Liu wrote:
> This patch adds driver for UltraSoc SMB(System Memory Buffer)
> device. SMB provides a way to buffer messages from ETM, and
> store these CPU instructions in system memory.
> 
> SMB is developed by UltraSoc technology, which is acquired by
> Siemens, and we still use "UltraSoc" to name driver.
> 
> Signed-off-by: Qi Liu <liuqi115@huawei.com>
> Tested-by: JunHao He <hejunhao2@hisilicon.com>
> ---
>   drivers/hwtracing/coresight/Kconfig        |  10 +
>   drivers/hwtracing/coresight/Makefile       |   1 +
>   drivers/hwtracing/coresight/ultrasoc-smb.c | 643 +++++++++++++++++++++
>   drivers/hwtracing/coresight/ultrasoc-smb.h | 106 ++++
>   4 files changed, 760 insertions(+)
>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h
> 
> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> index 514a9b8086e3..4380eb1a0a73 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -201,4 +201,14 @@ config CORESIGHT_TRBE
>   
>   	  To compile this driver as a module, choose M here: the module will be
>   	  called coresight-trbe.
> +config ULTRASOC_SMB
> +	tristate "Ultrasoc system memory buffer drivers"
> +	depends on ACPI && ARM64 && CORESIGHT_LINKS_AND_SINKS
> +	help
> +	  This driver provides support for the Ultrasoc system memory buffer (SMB).
> +	  SMB is responsible for receiving the trace data from Coresight ETM devices
> +	  and storing them to a system buffer.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ultrasoc-smb.
>   endif
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index b6c4a48140ec..344dba8d6ff8 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -27,3 +27,4 @@ obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o
>   obj-$(CONFIG_CORESIGHT_TRBE) += coresight-trbe.o
>   coresight-cti-y := coresight-cti-core.o	coresight-cti-platform.o \
>   		   coresight-cti-sysfs.o
> +obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o
> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
> new file mode 100644
> index 000000000000..9a93b7fc7bda
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
> @@ -0,0 +1,643 @@
> +// SPDX-License-Identifier: MIT/GPL
> +/*
> + * Siemens System Memory Buffer driver.
> + * Copyright(c) 2021, HiSilicon Limited.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/circ_buf.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +
> +#include "ultrasoc-smb.h"
> +
> +DEFINE_CORESIGHT_DEVLIST(sink_devs, "ultra_smb");
> +
> +#define ULTRASOC_SMB_DSM_UUID	"82ae1283-7f6a-4cbe-aa06-53e8fb24db18"
> +
> +static bool smb_buffer_is_empty(struct smb_drv_data *drvdata)
> +{
> +	u32 buf_status = readl(drvdata->base + SMB_LB_INT_STS);
> +
> +	return buf_status & BIT(0) ? false : true;
> +}
> +
> +static bool smb_buffer_cmp_pointer(struct smb_drv_data *drvdata)
> +{
> +	u32 wr_offset, rd_offset;
> +
> +	wr_offset = readl(drvdata->base + SMB_LB_WR_ADDR);
> +	rd_offset = readl(drvdata->base + SMB_LB_RD_ADDR);
> +	return wr_offset == rd_offset;
> +}
> +
> +static void smb_reset_buffer_status(struct smb_drv_data *drvdata)
> +{
> +	writel(0xf, drvdata->base + SMB_LB_INT_STS);
> +}
> +
> +/* Purge data remaining in hardware path in case them influence next trace */
> +static void smb_purge_data(struct smb_drv_data *drvdata)
> +{
> +	writel(0x1, drvdata->base + SMB_LB_PURGE);
> +}
> +
> +static void smb_update_data_size(struct smb_drv_data *drvdata)
> +{
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +	u32 write_offset;
> +
> +	smb_purge_data(drvdata);
> +	if (smb_buffer_cmp_pointer(drvdata)) {
> +		if (smb_buffer_is_empty(drvdata))
> +			sdb->data_size = 0;
> +		else
> +			sdb->data_size = sdb->buf_size;

What happens when the buffer is full ? Does the sink stop writing ?
Or does it keep on overwriting in a circular buffer mode ?
If it does keep overwriting, we would need to make sure to update the
sdb->rd_offset so that we provide the latest data (in smb_read())?
If it doesn't overwrite, I think this logic could be simpler (similar
to the tmc-et* circular buffer mode calculation.


> +		return;
> +	}
> +
> +	write_offset = readl(drvdata->base + SMB_LB_WR_ADDR) - sdb->start_addr;
> +	sdb->data_size = CIRC_CNT(write_offset, sdb->rd_offset, sdb->buf_size);
> +}
> +
> +static int smb_open(struct inode *inode, struct file *file)
> +{
> +	struct smb_drv_data *drvdata = container_of(file->private_data,
> +					struct smb_drv_data, miscdev);
> +
> +	if (local_cmpxchg(&drvdata->reading, 0, 1))

I believe this must be done in the smb_read(). Please see my comment
for smb_disable()

> +		return -EBUSY;
> +
> +	return 0;
> +}
> +
> +static ssize_t smb_read(struct file *file, char __user *data, size_t len,
> +			loff_t *ppos)
> +{
> +	struct smb_drv_data *drvdata = container_of(file->private_data,
> +						struct smb_drv_data, miscdev);
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +	struct device *dev = &drvdata->csdev->dev;
> +	unsigned long flags;
> +	int to_copy = 0;
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> +	if (atomic_read(drvdata->csdev->refcnt)) {
> +		spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +		return -EBUSY;
> +	}
> +
> +	if (!sdb->data_size) {
> +		smb_update_data_size(drvdata);
> +		if (!sdb->data_size)
> +			goto out;
> +	}
> +
> +	to_copy = min(sdb->data_size, len);
> +
> +	/* Copy parts of trace data when read pointer wrap around SMB buffer */
> +	if (sdb->rd_offset + to_copy > sdb->buf_size)
> +		to_copy = sdb->buf_size - sdb->rd_offset;
> +
> +	if (copy_to_user(data, (void *)sdb->buf_base + sdb->rd_offset,
> +			 to_copy)) {
> +		dev_dbg(dev, "Failed to copy data to user.\n");
> +		to_copy = -EFAULT;
> +		goto out;
> +	}
> +
> +	*ppos += to_copy;
> +	sdb->data_size -= to_copy;
> +	sdb->rd_offset += to_copy;
> +	sdb->rd_offset %= sdb->buf_size;
> +	writel(sdb->start_addr + sdb->rd_offset,
> +	       drvdata->base + SMB_LB_RD_ADDR);
> +	dev_dbg(dev, "%d bytes copied.\n", to_copy);
> +out:
> +	if (!sdb->data_size)
> +		smb_reset_buffer_status(drvdata);
> +	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +	return to_copy;
> +}
> +
> +static int smb_release(struct inode *inode, struct file *file)
> +{
> +	struct smb_drv_data *drvdata = container_of(file->private_data,
> +						struct smb_drv_data, miscdev);
> +	local_set(&drvdata->reading, 0);
> +	return 0;
> +}
> +
> +static const struct file_operations smb_fops = {
> +	.owner		= THIS_MODULE,
> +	.open		= smb_open,
> +	.read		= smb_read,
> +	.release	= smb_release,
> +	.llseek		= no_llseek,
> +};
> +
> +smb_reg(read_pos, SMB_LB_RD_ADDR);
> +smb_reg(write_pos, SMB_LB_WR_ADDR);
> +smb_reg(buf_status, SMB_LB_INT_STS);
> +
> +static ssize_t buf_size_show(struct device *dev, struct device_attribute *attr,
> +			     char *buf)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(dev->parent);
> +
> +	return sysfs_emit(buf, "0x%lx\n", drvdata->sdb.buf_size);
> +}
> +static DEVICE_ATTR_RO(buf_size);
> +
> +static struct attribute *smb_sink_attrs[] = {
> +	&dev_attr_read_pos.attr,
> +	&dev_attr_write_pos.attr,
> +	&dev_attr_buf_status.attr,
> +	&dev_attr_buf_size.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group smb_sink_group = {
> +	.attrs = smb_sink_attrs,
> +	.name = "mgmt",
> +};
> +
> +static const struct attribute_group *smb_sink_groups[] = {
> +	&smb_sink_group,
> +	NULL,
> +};
> +
> +static int smb_set_perf_buffer(struct perf_output_handle *handle)
> +{
> +	struct cs_buffers *buf = etm_perf_sink_config(handle);
> +	u32 head;
> +
> +	if (!buf)
> +		return -EINVAL;
> +
> +	/* Wrap head around to the amount of space we have */
> +	head = handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1);
> +
> +	/* Find the page to write to and offset within that page */
> +	buf->cur = head / PAGE_SIZE;
> +	buf->offset = head % PAGE_SIZE;
> +
> +	local_set(&buf->data_size, 0);
> +
> +	return 0;
> +}
> +
> +static void smb_enable_hw(struct smb_drv_data *drvdata)
> +{
> +	writel(0x1, drvdata->base + SMB_GLOBAL_EN);
> +}
> +
> +static void smb_disable_hw(struct smb_drv_data *drvdata)
> +{
> +	writel(0x0, drvdata->base + SMB_GLOBAL_EN);
> +}
> +
> +static int smb_enable_sysfs(struct coresight_device *csdev)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	unsigned long flags;
> +	int ret = 0;
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +	if (drvdata->mode == CS_MODE_PERF) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	if (drvdata->mode == CS_MODE_DISABLED) {
> +		smb_enable_hw(drvdata);
> +		drvdata->mode = CS_MODE_SYSFS;
> +	}
> +
> +	atomic_inc(csdev->refcnt);
> +out:
> +	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +	return ret;
> +}
> +
> +static int smb_enable_perf(struct coresight_device *csdev, void *data)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	struct device *dev = &drvdata->csdev->dev;
> +	struct perf_output_handle *handle = data;
> +	struct cs_buffers *buf = etm_perf_sink_config(handle);
> +	unsigned long flags;
> +	int ret = 0;
> +	pid_t pid;
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +	if (drvdata->mode == CS_MODE_SYSFS) {
> +		dev_dbg(dev, "Device is already in used by sysfs.\n");
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	/* Get a handle on the pid of the target process */
> +	pid = buf->pid;
> +	if (drvdata->pid != -1 && drvdata->pid != pid) { > +		dev_dbg(dev, "Device is already in used by other session.\n");
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	/* The sink is already enabled by this session */
> +	if (drvdata->pid == pid) {
> +		atomic_inc(csdev->refcnt);
> +		goto out;
> +	}
> +
> +	ret = smb_set_perf_buffer(handle);
> +	if (ret)
> +		goto out;
> +
> +	smb_enable_hw(drvdata);
> +	drvdata->pid = pid;
> +	drvdata->mode = CS_MODE_PERF;
> +	atomic_inc(csdev->refcnt);
> +out:
> +	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +	return ret;
> +}
> +
> +static int smb_enable(struct coresight_device *csdev, u32 mode, void *data)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	int ret;
> +
> +	/* Do nothing if trace data is reading by other interface now */
> +	if (local_read(&drvdata->reading))
> +		return -EBUSY;
> + > +	switch (mode) {
> +	case CS_MODE_SYSFS:
> +		ret = smb_enable_sysfs(csdev);
> +		break;
> +	case CS_MODE_PERF:
> +		ret = smb_enable_perf(csdev, data);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	if (ret)
> +		return ret;
> +	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled.\n");
> +
> +	return 0;
> +}
> +
> +static int smb_disable(struct coresight_device *csdev)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> +	if (local_read(&drvdata->reading)) {
> +		spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +		return -EBUSY;
> +	}
> +

This is a bit confusing. So, we don't allow "read" when a session
is in progress (via refcnt check in smb_read()). But the flag,
drvdata->reading is set as soon as we open(). And we fail the disable
if the drvdata->reading is set. I guess, we should move the setting
of the drvdata->reading to smb_read() and set it for the first case
where we are able to read.
Otherwise we could see, something like:

CPU0: smb_enable() 		# success, SMB is on
CPU1: open(/dev/usmb0) # -> set drvdata->reading
..
CPU0: smb_disable() # returns EBUSY since drvdata->reading is on.
CPU1: read(fd)      # returns EBUSY since there is a refcnt.



> +	if (atomic_dec_return(csdev->refcnt)) {
> +		spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +		return -EBUSY;
> +	}
> +
> +	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
> +	smb_disable_hw(drvdata);
> +	smb_purge_data(drvdata);
> +
> +	/*
> +	 * In perf mode, sink->disable is called after sink->update_buffer, so
> +	 * need to synchronize the read pointer to write pointer, to make sure
> +	 * these purged data won't influence next trace.
> +	 */
> +	if (drvdata->mode == CS_MODE_PERF)
> +		writel(readl(drvdata->base + SMB_LB_WR_ADDR),
> +		       drvdata->base + SMB_LB_RD_ADDR);
> +
> +	/* Dissociate from the target process. */
> +	drvdata->pid = -1;
> +	drvdata->mode = CS_MODE_DISABLED;
> +	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +
> +	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled.\n");
> +	return 0;
> +}
> +
> +static void *smb_alloc_buffer(struct coresight_device *csdev,
> +			      struct perf_event *event, void **pages,
> +			      int nr_pages, bool overwrite)
> +{
> +	struct cs_buffers *buf;
> +	int node;
> +
> +	node = (event->cpu == -1) ? NUMA_NO_NODE : cpu_to_node(event->cpu);
> +	buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);
> +	if (!buf)
> +		return NULL;
> +
> +	buf->snapshot = overwrite;
> +	buf->nr_pages = nr_pages;
> +	buf->data_pages = pages;
> +	buf->pid = task_pid_nr(event->owner);
> +
> +	return buf;
> +}
> +
> +static void smb_free_buffer(void *config)
> +{
> +	struct cs_buffers *buf = config;
> +
> +	kfree(buf);
> +}
> +
> +static void smb_sync_perf_buffer(struct smb_drv_data *drvdata,
> +				 struct cs_buffers *buf,
> +				 unsigned long data_size)
> +{
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +	char **dst_pages = (char **)buf->data_pages;
> +	unsigned long page_offset = buf->offset;
> +	unsigned int cur = buf->cur;
> +	unsigned long to_copy;
> +
> +	while (data_size) {
> +		unsigned long page_space = PAGE_SIZE - page_offset;
> +
> +		/* Copy parts of trace data when read pointer wrap around */
> +		if (sdb->rd_offset + page_space > sdb->buf_size)
> +			to_copy = sdb->buf_size - sdb->rd_offset;
> +		else
> +			to_copy = min(data_size, page_space);
> +
> +		memcpy_fromio(dst_pages[cur] + page_offset,
> +			      sdb->buf_base + sdb->rd_offset, to_copy);
> +
> +		page_offset += to_copy;
> +		if (page_offset >= PAGE_SIZE) {
> +			page_offset = 0;
> +			cur++;
> +			cur %= buf->nr_pages;
> +		}
> +		data_size -= to_copy;
> +		sdb->rd_offset += to_copy;
> +		sdb->rd_offset %= sdb->buf_size;
> +	}
> +
> +	sdb->data_size = 0;
> +	writel(sdb->start_addr + sdb->rd_offset,
> +	       drvdata->base + SMB_LB_RD_ADDR);
> +	smb_reset_buffer_status(drvdata);
> +}
> +
> +static unsigned long smb_update_buffer(struct coresight_device *csdev,
> +				       struct perf_output_handle *handle,
> +				       void *sink_config)
> +{
> +	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	struct smb_data_buffer *sdb = &drvdata->sdb;
> +	struct cs_buffers *buf = sink_config;
> +	unsigned long data_size = 0;
> +	unsigned long flags;
> +	bool lost = false;
> +
> +	if (!buf)
> +		return 0;
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> +	/* Don't do anything if another tracer is using this sink. */
> +	if (atomic_read(csdev->refcnt) != 1)
> +		goto out;
> +
> +	smb_update_data_size(drvdata);

Are we allowed to call this when the SMB is ON ? In perf mode, we call
the update_buffer() before disabling the "sink". So, care must be taken
to stop the SMB if needed to make sure the registers are read properly.


Rest looks fine to me.


Suzuki

Re: [PATCH v5 1/2] drivers/coresight: Add UltraSoc System Memory Buffer driver

[liuqi (BA)]

Hi Suzuki,

thanks for your review, some replies below.

On 2022/5/6 8:26, Suzuki K Poulose wrote:
> Hi Qi Liu
> 
> Apologies for the delay. I have some more comments below.
>  > On 16/04/2022 09:39, Qi Liu wrote:
>> This patch adds driver for UltraSoc SMB(System Memory Buffer)
>> device. SMB provides a way to buffer messages from ETM, and
>> store these CPU instructions in system memory.
>>
>> SMB is developed by UltraSoc technology, which is acquired by
>> Siemens, and we still use "UltraSoc" to name driver.
>>
>> Signed-off-by: Qi Liu <liuqi115@huawei.com>
>> Tested-by: JunHao He <hejunhao2@hisilicon.com>
>> ---
>>   drivers/hwtracing/coresight/Kconfig        |  10 +
>>   drivers/hwtracing/coresight/Makefile       |   1 +
>>   drivers/hwtracing/coresight/ultrasoc-smb.c | 643 +++++++++++++++++++++
>>   drivers/hwtracing/coresight/ultrasoc-smb.h | 106 ++++
>>   4 files changed, 760 insertions(+)
>>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.c
>>   create mode 100644 drivers/hwtracing/coresight/ultrasoc-smb.h
>>
>> diff --git a/drivers/hwtracing/coresight/Kconfig 
>> b/drivers/hwtracing/coresight/Kconfig
>> index 514a9b8086e3..4380eb1a0a73 100644
>> --- a/drivers/hwtracing/coresight/Kconfig
>> +++ b/drivers/hwtracing/coresight/Kconfig
>> @@ -201,4 +201,14 @@ config CORESIGHT_TRBE
>>         To compile this driver as a module, choose M here: the module 
>> will be
>>         called coresight-trbe.
>> +config ULTRASOC_SMB
>> +    tristate "Ultrasoc system memory buffer drivers"
>> +    depends on ACPI && ARM64 && CORESIGHT_LINKS_AND_SINKS
>> +    help
>> +      This driver provides support for the Ultrasoc system memory 
>> buffer (SMB).
>> +      SMB is responsible for receiving the trace data from Coresight 
>> ETM devices
>> +      and storing them to a system buffer.
>> +
>> +      To compile this driver as a module, choose M here: the module 
>> will be
>> +      called ultrasoc-smb.
>>   endif
>> diff --git a/drivers/hwtracing/coresight/Makefile 
>> b/drivers/hwtracing/coresight/Makefile
>> index b6c4a48140ec..344dba8d6ff8 100644
>> --- a/drivers/hwtracing/coresight/Makefile
>> +++ b/drivers/hwtracing/coresight/Makefile
>> @@ -27,3 +27,4 @@ obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o
>>   obj-$(CONFIG_CORESIGHT_TRBE) += coresight-trbe.o
>>   coresight-cti-y := coresight-cti-core.o    coresight-cti-platform.o \
>>              coresight-cti-sysfs.o
>> +obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o
>> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c 
>> b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> new file mode 100644
>> index 000000000000..9a93b7fc7bda
>> --- /dev/null
>> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
>> @@ -0,0 +1,643 @@
>> +// SPDX-License-Identifier: MIT/GPL
>> +/*
>> + * Siemens System Memory Buffer driver.
>> + * Copyright(c) 2021, HiSilicon Limited.
>> + */
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/circ_buf.h>
>> +#include <linux/err.h>
>> +#include <linux/module.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/platform_device.h>
>> +
>> +#include "ultrasoc-smb.h"
>> +
>> +DEFINE_CORESIGHT_DEVLIST(sink_devs, "ultra_smb");
>> +
>> +#define ULTRASOC_SMB_DSM_UUID    "82ae1283-7f6a-4cbe-aa06-53e8fb24db18"
>> +
>> +static bool smb_buffer_is_empty(struct smb_drv_data *drvdata)
>> +{
>> +    u32 buf_status = readl(drvdata->base + SMB_LB_INT_STS);
>> +
>> +    return buf_status & BIT(0) ? false : true;
>> +}
>> +
>> +static bool smb_buffer_cmp_pointer(struct smb_drv_data *drvdata)
>> +{
>> +    u32 wr_offset, rd_offset;
>> +
>> +    wr_offset = readl(drvdata->base + SMB_LB_WR_ADDR);
>> +    rd_offset = readl(drvdata->base + SMB_LB_RD_ADDR);
>> +    return wr_offset == rd_offset;
>> +}
>> +
>> +static void smb_reset_buffer_status(struct smb_drv_data *drvdata)
>> +{
>> +    writel(0xf, drvdata->base + SMB_LB_INT_STS);
>> +}
>> +
>> +/* Purge data remaining in hardware path in case them influence next 
>> trace */
>> +static void smb_purge_data(struct smb_drv_data *drvdata)
>> +{
>> +    writel(0x1, drvdata->base + SMB_LB_PURGE);
>> +}
>> +
>> +static void smb_update_data_size(struct smb_drv_data *drvdata)
>> +{
>> +    struct smb_data_buffer *sdb = &drvdata->sdb;
>> +    u32 write_offset;
>> +
>> +    smb_purge_data(drvdata);
>> +    if (smb_buffer_cmp_pointer(drvdata)) {
>> +        if (smb_buffer_is_empty(drvdata))
>> +            sdb->data_size = 0;
>> +        else
>> +            sdb->data_size = sdb->buf_size;
> 
> What happens when the buffer is full ? Does the sink stop writing ?
> Or does it keep on overwriting in a circular buffer mode ?
> If it does keep overwriting, we would need to make sure to update the
> sdb->rd_offset so that we provide the latest data (in smb_read())?
> If it doesn't overwrite, I think this logic could be simpler (similar
> to the tmc-et* circular buffer mode calculation.
> 

sink will stop writing when the buffer is full, and I'll simplify this 
function like this:

static void smb_buffer_is_full(struct smb_drv_data *drvdata)
{
	if (smb_buffer_cmp_pointer(drvdata) && !smb_buffer_is_empty(drvdata))
		return true;
	return false;
}

static void smb_update_data_size(struct smb_drv_data *drvdata)
{
	struct smb_data_buffer *sdb = &drvdata->sdb;
	u32 write_offset;

	if (smb_buffer_is_full(drvdata)) {
		sdb->data_size = sdb->buf_size;
		return;
	}

	write_offset = readl(drvdata->base + SMB_LB_WR_ADDR) -
sdb->start_addr;
	sdb->data_size = CIRC_CNT(write_offset, sdb->rd_offset,
sdb->buf_size);
}
> 
>> +        return;
>> +    }
>> +
>> +    write_offset = readl(drvdata->base + SMB_LB_WR_ADDR) - 
>> sdb->start_addr;
>> +    sdb->data_size = CIRC_CNT(write_offset, sdb->rd_offset, 
>> sdb->buf_size);
>> +}
>> +
>> +static int smb_open(struct inode *inode, struct file *file)
>> +{
>> +    struct smb_drv_data *drvdata = container_of(file->private_data,
>> +                    struct smb_drv_data, miscdev);
>> +
>> +    if (local_cmpxchg(&drvdata->reading, 0, 1))
> 
> I believe this must be done in the smb_read(). Please see my comment
> for smb_disable()
> 
got it, I'll change this like:

static int smb_open(struct inode *inode, struct file *file)
{
	struct smb_drv_data *drvdata = container_of(file->private_data, struct 
smb_drv_data, miscdev);
	ret = 0;

	spin_lock_irqsave(&drvdata->spinlock, flags);

	if (drvdata->reading) {
		ret = -EBUSY;
		goto out;
	}

	if (drvdata->mode == CS_MODE_PERF) {
		ret = -EINVAL;
		goto out;
	}

	if (atomic_read(drvdata->csdev->refcnt))
		ret = -EBUSY;

out:
	spin_unlock_irqrestore(&drvdata->spinlock, flags);
	return ret;
}
>> +        return -EBUSY;
>> +
>> +    return 0;
>> +}
>> +
>> +static ssize_t smb_read(struct file *file, char __user *data, size_t 
>> len,
>> +            loff_t *ppos)
>> +{
>> +    struct smb_drv_data *drvdata = container_of(file->private_data,
>> +                        struct smb_drv_data, miscdev);
>> +    struct smb_data_buffer *sdb = &drvdata->sdb;
>> +    struct device *dev = &drvdata->csdev->dev;
>> +    unsigned long flags;
>> +    int to_copy = 0;
>> +
>> +    spin_lock_irqsave(&drvdata->spinlock, flags);
>> +
>> +    if (atomic_read(drvdata->csdev->refcnt)) {
>> +        spin_unlock_irqrestore(&drvdata->spinlock, flags);
>> +        return -EBUSY;
>> +    }
>> +
>> +    if (!sdb->data_size) {
>> +        smb_update_data_size(drvdata);
>> +        if (!sdb->data_size)
>> +            goto out;
>> +    }
>> +
>> +    to_copy = min(sdb->data_size, len);
>> +
>> +    /* Copy parts of trace data when read pointer wrap around SMB 
>> buffer */
>> +    if (sdb->rd_offset + to_copy > sdb->buf_size)
>> +        to_copy = sdb->buf_size - sdb->rd_offset;
>> +
>> +    if (copy_to_user(data, (void *)sdb->buf_base + sdb->rd_offset,
>> +             to_copy)) {
>> +        dev_dbg(dev, "Failed to copy data to user.\n");
>> +        to_copy = -EFAULT;
>> +        goto out;
>> +    }
>> +
>> +    *ppos += to_copy;
>> +    sdb->data_size -= to_copy;
>> +    sdb->rd_offset += to_copy;
>> +    sdb->rd_offset %= sdb->buf_size;
>> +    writel(sdb->start_addr + sdb->rd_offset,
>> +           drvdata->base + SMB_LB_RD_ADDR);
>> +    dev_dbg(dev, "%d bytes copied.\n", to_copy);
>> +out:
>> +    if (!sdb->data_size)
>> +        smb_reset_buffer_status(drvdata);
>> +    spin_unlock_irqrestore(&drvdata->spinlock, flags);
>> +    return to_copy;
>> +}
>> +
>> +static int smb_release(struct inode *inode, struct file *file)
>> +{
>> +    struct smb_drv_data *drvdata = container_of(file->private_data,
>> +                        struct smb_drv_data, miscdev);
>> +    local_set(&drvdata->reading, 0);
>> +    return 0;
>> +}
>> +

[...]
>> +
>> +static int smb_disable(struct coresight_device *csdev)
>> +{
>> +    struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
>> +    unsigned long flags;
>> +
>> +    spin_lock_irqsave(&drvdata->spinlock, flags);
>> +
>> +    if (local_read(&drvdata->reading)) {
>> +        spin_unlock_irqrestore(&drvdata->spinlock, flags);
>> +        return -EBUSY;
>> +    }
>> +
> 
> This is a bit confusing. So, we don't allow "read" when a session
> is in progress (via refcnt check in smb_read()). But the flag,
> drvdata->reading is set as soon as we open(). And we fail the disable
> if the drvdata->reading is set. I guess, we should move the setting
> of the drvdata->reading to smb_read() and set it for the first case
> where we are able to read.
> Otherwise we could see, something like:
> 
> CPU0: smb_enable()         # success, SMB is on
> CPU1: open(/dev/usmb0) # -> set drvdata->reading
> ..
> CPU0: smb_disable() # returns EBUSY since drvdata->reading is on.
> CPU1: read(fd)      # returns EBUSY since there is a refcnt.
> 
> 
got it, I'll change this next version, thanks.
> 
>> +    if (atomic_dec_return(csdev->refcnt)) {
>> +        spin_unlock_irqrestore(&drvdata->spinlock, flags);
>> +        return -EBUSY;
>> +    }
>> +
>> +    WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
>> +    smb_disable_hw(drvdata);
>> +    smb_purge_data(drvdata);
>> +
>> +    /*
>> +     * In perf mode, sink->disable is called after 
>> sink->update_buffer, so
+    buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);

[...]
>> +
>> +static unsigned long smb_update_buffer(struct coresight_device *csdev,
>> +                       struct perf_output_handle *handle,
>> +                       void *sink_config)
>> +{
>> +    struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
>> +    struct smb_data_buffer *sdb = &drvdata->sdb;
>> +    struct cs_buffers *buf = sink_config;
>> +    unsigned long data_size = 0;
>> +    unsigned long flags;
>> +    bool lost = false;
>> +
>> +    if (!buf)
>> +        return 0;
>> +
>> +    spin_lock_irqsave(&drvdata->spinlock, flags);
>> +
>> +    /* Don't do anything if another tracer is using this sink. */
>> +    if (atomic_read(csdev->refcnt) != 1)
>> +        goto out;
>> +
>> +    smb_update_data_size(drvdata);
> 
> Are we allowed to call this when the SMB is ON ? In perf mode, we call
> the update_buffer() before disabling the "sink". So, care must be taken
> to stop the SMB if needed to make sure the registers are read properly.

got it, will do disable smb before smb_update_data_size.
> 
> 
> Rest looks fine to me.
> 
> 
> Suzuki
> .
Thanks,
Qi

Re: [PATCH v5 2/2] Documentation: Add document for UltraSoc SMB drivers

[liuqi (BA)]

Hi Suzuki,

thanks for your review, some replies inline.

On 2022/5/6 0:22, Suzuki K Poulose wrote:
> On 16/04/2022 09:39, Qi Liu wrote:
>> This patch bring in a documentation for UltraSoc SMB drivers.
>> It simple descripts the device, sysfs interface and the
>> firmware bindings.
>>
>> Signed-off-by: Qi Liu <liuqi115@huawei.com>
>> ---
>>   .../trace/coresight/ultrasoc-smb.rst          | 79 +++++++++++++++++++
>>   1 file changed, 79 insertions(+)
>>   create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst
>>
>> diff --git a/Documentation/trace/coresight/ultrasoc-smb.rst 
>> b/Documentation/trace/coresight/ultrasoc-smb.rst
>> new file mode 100644
>> index 000000000000..024fa4492f42
>> --- /dev/null
>> +++ b/Documentation/trace/coresight/ultrasoc-smb.rst
>> @@ -0,0 +1,79 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +======================================
>> +UltraSoc - HW Assisted Tracing on SoC
>> +======================================
>> +   :Author:   Qi Liu <liuqi115@huawei.com>
>> +   :Date:     March 2022
>> +
>> +Introduction
>> +------------
>> +
>> +UltraSoc SMB is a per SCCL hardware, and it provides a way to buffer 
>> and store
> 
> nit: what is SCCL ?

SCCL is super CPU cluster, I'll add the full name next time.

> 
>> +CPU trace messages in a region of shared system memory. SMB is 
>> plugged as
>> +a coresight sink device and the corresponding trace generators (ETM) are
>> +plugged in as source devices.
>> +
>> +Sysfs files and directories
>> +---------------------------
>> +
>> +The SMB devices appear on the existing coresight bus alongside the other
>> +coresight devices::
>> +
>> +    $# ls /sys/bus/coresight/devices/
>> +    ultra_smb0   ultra_smb1   ultra_smb2   ultra_smb3
>> +
>> +The ``ultra_smb<N>`` named SMB associated with SCCL.::
>> +
>> +    $# ls /sys/bus/coresight/devices/ultra_smb0
>> +    enable_sink   mgmt
>> +    $# ls /sys/bus/coresight/devices/ultra_smb0/mgmt
>> +    buf_size  buf_status  read_pos  write_pos
>> +
>> +*Key file items are:-*
>> +   * ``read_pos``: Shows the value held by UltraSoc SMB Read Pointer 
>> register.
>> +   * ``write_pos``: Shows the value held by UltraSoc SMB Write 
>> Pointer register.
>> +   * ``buf_status``: Shows the value held by UltraSoc SMB status 
>> register.
>> +             BIT(0) is zero means buffer is empty.
>> +   * ``buf_size``: Shows the buffer size of each UltraSoc SMB device.
>> +
>> +Firmware Bindings
>> +---------------------------
>> +
>> +Firmware binding of SMB device describes SMB device indentifier, 
>> resource
>> +information and graph structure.
>> +
>> +SMB is platform device and device id is "HISI03A1", resource of 
>> device is
>> +declared using the _CRS method. Each SMB must present two base address,
>> +the first one is the configuration base address of SMB device, the 
>> second
>> +one is the base address of shared system memory.
>> +
>> +examples::
>> +
>> +    Device(USMB) {                                               \
>> +      Name(_HID, "HISI03A1")                                     \
>> +      Name(_CRS, ResourceTemplate() {                            \
>> +          MEM_RESRC(0x95100000, 0x951FFFFF, 0x100000)            \
>> +          MEM_RESRC(0x50000000, 0x53FFFFFF, 0x4000000)           \
>> +      })                                                         \
> 
> 
>> +      Name(_DSD, Package() {                                     \
>> +        ToUUID("ab02a46b-74c7-45a2-bd68-f7d344ef2153"),          \
> 
> nit: May be add a comment here to explain, use Arm CoreSight Graph
> ACPI bindings to describe the connections.

got it, will add a comment above, thanks.
> 
>> +        Package() {                                              \
>> +          0,                                                     \
>> +          1,                                                     \
>> +          Package() {                                            \
>> +            1,                                                   \
>> +            ToUUID("3ecbc8b6-1d0e-4fb3-8107-e627f805c6cd"),      \
>> +            8,                                                   \
>> +            Package() {0x8, 0, \_SB.S00.SL11.CL28.F008, 0},       \
>> +            Package() {0x9, 0, \_SB.S00.SL11.CL29.F009, 0},       \
>> +            Package() {0xa, 0, \_SB.S00.SL11.CL2A.F010, 0},       \
>> +            Package() {0xb, 0, \_SB.S00.SL11.CL2B.F011, 0},       \
>> +            Package() {0xc, 0, \_SB.S00.SL11.CL2C.F012, 0},       \
>> +            Package() {0xd, 0, \_SB.S00.SL11.CL2D.F013, 0},       \
>> +            Package() {0xe, 0, \_SB.S00.SL11.CL2E.F014, 0},       \
>> +            Package() {0xf, 0, \_SB.S00.SL11.CL2F.F015, 0},       \
>> +          }                                                      \
> 
> Interesting, are there multiple input ports for the SMB ? We haven't
> seen an instance of a "sink" that supports this. So, would be
> interesting to see how the driver copes with that scenario.
> 
> Suzuki
> 
> yes, as there are 8 clusters in a SCCL, and each cluster use one funnel 
device to transmit core trace data, so SMB has 8 input funnel ports.

Thanks,
Qi
> 
>> +        }                                                        \
>> +      })                                                         \
>> +    }
> 
> .