Re: [PATCH v5 1/2] drivers/coresight: Add UltraSoc System Memory Buffer driver
From: liuqi (BA)
Date: Thu May 05 2022 - 22:36:05 EST
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@xxxxxxxxxx>
Tested-by: JunHao He <hejunhao2@xxxxxxxxxxxxx>
---
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