Skip to content

Commit

Permalink
coresight: tmc: Make etr buffer mode user configurable from sysfs
Browse files Browse the repository at this point in the history 
Currently TMC-ETR automatically selects the buffer mode from all available
methods in the following sequentially fallback manner - also in that order.

1. FLAT mode with or without IOMMU
2. TMC-ETR-SG (scatter gather) mode when available
3. CATU mode when available

But this order might not be ideal for all situations. For example if there
is a CATU connected to ETR, it may be better to use TMC-ETR scatter gather
method, rather than CATU. But hard coding such order changes will prevent
us from testing or using a particular mode. This change provides following
new sysfs tunables for the user to control TMC-ETR buffer mode explicitly,
if required. This adds following new sysfs files for buffer mode selection
purpose explicitly in the user space.

/sys/bus/coresight/devices/tmc_etr<N>/buf_modes_available
/sys/bus/coresight/devices/tmc_etr<N>/buf_mode_preferred

$ cat buf_modes_available
auto flat tmc-sg catu	------------------> Supported TMC-ETR buffer modes

$ echo catu > buf_mode_preferred   -------> Explicit buffer mode request

But explicit user request has to be within supported ETR buffer modes only.
These sysfs interface files are exclussive to ETR, and hence these are not
available for other TMC devices such as ETB or ETF etc.

A new auto' mode (i.e ETR_MODE_AUTO) has been added to help fallback to the
existing default behaviour, when user provided preferred buffer mode fails.
ETR_MODE_FLAT and ETR_MODE_AUTO are always available as preferred modes.

Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
[Fixup year in sysfs ABI documentation]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230818082112.554638-1-anshuman.khandual@arm.com
  • Loading branch information
Anshuman Khandual authored and Suzuki K Poulose committed Nov 16, 2023
1 parent e5d207b commit 2373699
Show file tree
Hide file tree
Showing 4 changed files with 131 additions and 14 deletions.
16 changes: 16 additions & 0 deletions Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -91,3 +91,19 @@ Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
Description: (RW) Size of the trace buffer for TMC-ETR when used in SYSFS
mode. Writable only for TMC-ETR configurations. The value
should be aligned to the kernel pagesize.

What: /sys/bus/coresight/devices/<memory_map>.tmc/buf_modes_available
Date: August 2023
KernelVersion: 6.7
Contact: Anshuman Khandual <anshuman.khandual@arm.com>
Description: (Read) Shows all supported Coresight TMC-ETR buffer modes available
for the users to configure explicitly. This file is avaialble only
for TMC ETR devices.

What: /sys/bus/coresight/devices/<memory_map>.tmc/buf_mode_preferred
Date: August 2023
KernelVersion: 6.7
Contact: Anshuman Khandual <anshuman.khandual@arm.com>
Description: (RW) Current Coresight TMC-ETR buffer mode selected. But user could
only provide a mode which is supported for a given ETR device. This
file is available only for TMC ETR devices.
15 changes: 13 additions & 2 deletions drivers/hwtracing/coresight/coresight-tmc-core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/io.h>
#include <linux/iommu.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
Expand Down Expand Up @@ -344,7 +345,14 @@ static const struct attribute_group coresight_tmc_mgmt_group = {
.name = "mgmt",
};

static const struct attribute_group *coresight_tmc_groups[] = {
static const struct attribute_group *coresight_etf_groups[] = {
&coresight_tmc_group,
&coresight_tmc_mgmt_group,
NULL,
};

static const struct attribute_group *coresight_etr_groups[] = {
&coresight_etr_group,
&coresight_tmc_group,
&coresight_tmc_mgmt_group,
NULL,
Expand Down Expand Up @@ -465,6 +473,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
drvdata->memwidth = tmc_get_memwidth(devid);
/* This device is not associated with a session */
drvdata->pid = -1;
drvdata->etr_mode = ETR_MODE_AUTO;

if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
drvdata->size = tmc_etr_get_default_buffer_size(dev);
Expand All @@ -474,16 +483,17 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
}

desc.dev = dev;
desc.groups = coresight_tmc_groups;

switch (drvdata->config_type) {
case TMC_CONFIG_TYPE_ETB:
desc.groups = coresight_etf_groups;
desc.type = CORESIGHT_DEV_TYPE_SINK;
desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
desc.ops = &tmc_etb_cs_ops;
dev_list = &etb_devs;
break;
case TMC_CONFIG_TYPE_ETR:
desc.groups = coresight_etr_groups;
desc.type = CORESIGHT_DEV_TYPE_SINK;
desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM;
desc.ops = &tmc_etr_cs_ops;
Expand All @@ -496,6 +506,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
dev_list = &etr_devs;
break;
case TMC_CONFIG_TYPE_ETF:
desc.groups = coresight_etf_groups;
desc.type = CORESIGHT_DEV_TYPE_LINKSINK;
desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
desc.subtype.link_subtype = CORESIGHT_DEV_SUBTYPE_LINK_FIFO;
Expand Down
111 changes: 99 additions & 12 deletions drivers/hwtracing/coresight/coresight-tmc-etr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,12 @@ struct etr_flat_buf {
size_t size;
};

struct etr_buf_hw {
bool has_iommu;
bool has_etr_sg;
bool has_catu;
};

/*
* etr_perf_buffer - Perf buffer used for ETR
* @drvdata - The ETR drvdaga this buffer has been allocated for.
Expand Down Expand Up @@ -830,6 +836,22 @@ static inline int tmc_etr_mode_alloc_buf(int mode,
}
}

static void get_etr_buf_hw(struct device *dev, struct etr_buf_hw *buf_hw)
{
struct tmc_drvdata *drvdata = dev_get_drvdata(dev->parent);

buf_hw->has_iommu = iommu_get_domain_for_dev(dev->parent);
buf_hw->has_etr_sg = tmc_etr_has_cap(drvdata, TMC_ETR_SG);
buf_hw->has_catu = !!tmc_etr_get_catu_device(drvdata);
}

static bool etr_can_use_flat_mode(struct etr_buf_hw *buf_hw, ssize_t etr_buf_size)
{
bool has_sg = buf_hw->has_catu || buf_hw->has_etr_sg;

return !has_sg || buf_hw->has_iommu || etr_buf_size < SZ_1M;
}

/*
* tmc_alloc_etr_buf: Allocate a buffer use by ETR.
* @drvdata : ETR device details.
Expand All @@ -843,23 +865,22 @@ static struct etr_buf *tmc_alloc_etr_buf(struct tmc_drvdata *drvdata,
int node, void **pages)
{
int rc = -ENOMEM;
bool has_etr_sg, has_iommu;
bool has_sg, has_catu;
struct etr_buf *etr_buf;
struct etr_buf_hw buf_hw;
struct device *dev = &drvdata->csdev->dev;

has_etr_sg = tmc_etr_has_cap(drvdata, TMC_ETR_SG);
has_iommu = iommu_get_domain_for_dev(dev->parent);
has_catu = !!tmc_etr_get_catu_device(drvdata);

has_sg = has_catu || has_etr_sg;

get_etr_buf_hw(dev, &buf_hw);
etr_buf = kzalloc(sizeof(*etr_buf), GFP_KERNEL);
if (!etr_buf)
return ERR_PTR(-ENOMEM);

etr_buf->size = size;

/* If there is user directive for buffer mode, try that first */
if (drvdata->etr_mode != ETR_MODE_AUTO)
rc = tmc_etr_mode_alloc_buf(drvdata->etr_mode, drvdata,
etr_buf, node, pages);

/*
* If we have to use an existing list of pages, we cannot reliably
* use a contiguous DMA memory (even if we have an IOMMU). Otherwise,
Expand All @@ -872,14 +893,13 @@ static struct etr_buf *tmc_alloc_etr_buf(struct tmc_drvdata *drvdata,
* Fallback to available mechanisms.
*
*/
if (!pages &&
(!has_sg || has_iommu || size < SZ_1M))
if (rc && !pages && etr_can_use_flat_mode(&buf_hw, size))
rc = tmc_etr_mode_alloc_buf(ETR_MODE_FLAT, drvdata,
etr_buf, node, pages);
if (rc && has_etr_sg)
if (rc && buf_hw.has_etr_sg)
rc = tmc_etr_mode_alloc_buf(ETR_MODE_ETR_SG, drvdata,
etr_buf, node, pages);
if (rc && has_catu)
if (rc && buf_hw.has_catu)
rc = tmc_etr_mode_alloc_buf(ETR_MODE_CATU, drvdata,
etr_buf, node, pages);
if (rc) {
Expand Down Expand Up @@ -1804,3 +1824,70 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)

return 0;
}

static const char *const buf_modes_str[] = {
[ETR_MODE_FLAT] = "flat",
[ETR_MODE_ETR_SG] = "tmc-sg",
[ETR_MODE_CATU] = "catu",
[ETR_MODE_AUTO] = "auto",
};

static ssize_t buf_modes_available_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct etr_buf_hw buf_hw;
ssize_t size = 0;

get_etr_buf_hw(dev, &buf_hw);
size += sysfs_emit(buf, "%s ", buf_modes_str[ETR_MODE_AUTO]);
size += sysfs_emit_at(buf, size, "%s ", buf_modes_str[ETR_MODE_FLAT]);
if (buf_hw.has_etr_sg)
size += sysfs_emit_at(buf, size, "%s ", buf_modes_str[ETR_MODE_ETR_SG]);

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

size += sysfs_emit_at(buf, size, "\n");
return size;
}
static DEVICE_ATTR_RO(buf_modes_available);

static ssize_t buf_mode_preferred_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct tmc_drvdata *drvdata = dev_get_drvdata(dev->parent);

return sysfs_emit(buf, "%s\n", buf_modes_str[drvdata->etr_mode]);
}

static ssize_t buf_mode_preferred_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t size)
{
struct tmc_drvdata *drvdata = dev_get_drvdata(dev->parent);
struct etr_buf_hw buf_hw;

get_etr_buf_hw(dev, &buf_hw);
if (sysfs_streq(buf, buf_modes_str[ETR_MODE_FLAT]))
drvdata->etr_mode = ETR_MODE_FLAT;
else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_ETR_SG]) && buf_hw.has_etr_sg)
drvdata->etr_mode = ETR_MODE_ETR_SG;
else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_CATU]) && buf_hw.has_catu)
drvdata->etr_mode = ETR_MODE_CATU;
else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_AUTO]))
drvdata->etr_mode = ETR_MODE_AUTO;
else
return -EINVAL;
return size;
}
static DEVICE_ATTR_RW(buf_mode_preferred);

static struct attribute *coresight_etr_attrs[] = {
&dev_attr_buf_modes_available.attr,
&dev_attr_buf_mode_preferred.attr,
NULL,
};

const struct attribute_group coresight_etr_group = {
.attrs = coresight_etr_attrs,
};
3 changes: 3 additions & 0 deletions drivers/hwtracing/coresight/coresight-tmc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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_AUTO, /* Use the default mechanism */
};

struct etr_buf_operations;
Expand Down Expand Up @@ -207,6 +208,7 @@ struct tmc_drvdata {
enum tmc_mem_intf_width memwidth;
u32 trigger_cntr;
u32 etr_caps;
enum etr_mode etr_mode;
struct idr idr;
struct mutex idr_mutex;
struct etr_buf *sysfs_buf;
Expand Down Expand Up @@ -334,5 +336,6 @@ void tmc_etr_set_catu_ops(const struct etr_buf_operations *catu);
void tmc_etr_remove_catu_ops(void);
struct etr_buf *tmc_etr_get_buffer(struct coresight_device *csdev,
enum cs_mode mode, void *data);
extern const struct attribute_group coresight_etr_group;

#endif

0 comments on commit 2373699

Please sign in to comment.