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Message-ID: <f1acfd07-7317-4b7e-bb81-ea9a894f25ac@arm.com>
Date: Thu, 3 Oct 2024 14:25:54 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Linu Cherian <lcherian@...vell.com>, mike.leach@...aro.org,
james.clark@....com
Cc: linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, robh@...nel.org,
krzk+dt@...nel.org, conor+dt@...nel.org, corbet@....net,
devicetree@...r.kernel.org, sgoutham@...vell.com, gcherian@...vell.com,
Anil Kumar Reddy <areddy3@...vell.com>, Tanmay Jagdale <tanmay@...vell.com>
Subject: Re: [PATCH v10 5/8] coresight: tmc: Add support for reading crash
data
Hi Linu
On 16/09/2024 11:34, Linu Cherian wrote:
> * Add support for reading crashdata using special device files.
> The special device files /dev/crash_tmc_xxx would be available
> for read file operation only when the crash data is valid.
>
> * User can read the crash data as below
>
> For example, for reading crash data from tmc_etf sink
>
> #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin
There are some comments below, please take a look.
>
> Signed-off-by: Anil Kumar Reddy <areddy3@...vell.com>
> Signed-off-by: Tanmay Jagdale <tanmay@...vell.com>
> Signed-off-by: Linu Cherian <lcherian@...vell.com>
> ---
> Changelog from v9:
> - Removed READ_CRASHDATA mode meant for special casing crashdata read
> - Added new fields full, len, offset to struct tmc_resrv_buf
Why do we need "full" ? See more on that below.
> so as to have a common read function for ETR and ETF
> - Introduced read file operation, tmc_crashdata_read
> specific to crashdata reads common for both ETR and ETF
> - Introduced is_tmc_crashdata_valid function
> Special device file /dev/crash_tmc_xxx will be available only when
> crashdata is valid.
> - Version checks added to crashdata validity checks
> - Mark crashdata as invalid when user starts tracing with ETR sink in
> "resrv" buffer mode
>
> .../hwtracing/coresight/coresight-tmc-core.c | 206 +++++++++++++++++-
> .../hwtracing/coresight/coresight-tmc-etf.c | 36 +++
> .../hwtracing/coresight/coresight-tmc-etr.c | 63 ++++++
> drivers/hwtracing/coresight/coresight-tmc.h | 18 +-
> include/linux/coresight.h | 12 +
> 5 files changed, 333 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
> index 54bf8ae2bff8..47b6b3f88750 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> @@ -105,6 +105,125 @@ u32 tmc_get_memwidth_mask(struct tmc_drvdata *drvdata)
> return mask;
> }
>
> +bool is_tmc_crashdata_valid(struct tmc_drvdata *drvdata)
> +{
> + struct tmc_crash_metadata *mdata;
> +
> + if (!tmc_has_reserved_buffer(drvdata) ||
> + !tmc_has_crash_mdata_buffer(drvdata))
> + return false;
> +
> + mdata = drvdata->crash_mdata.vaddr;
> +
> + /* Check version match */
> + if (mdata->version != CS_CRASHDATA_VERSION)
> + return false;
> +
> + /* Check data integrity of metadata */
> + if (mdata->crc32_mdata != find_crash_metadata_crc(mdata)) {
> + dev_dbg(&drvdata->csdev->dev,
> + "CRC mismatch in tmc crash metadata\n");
> + return false;
> + }
> + /* Check data integrity of tracedata */
> + if (mdata->crc32_tdata != find_crash_tracedata_crc(drvdata, mdata)) {
> + dev_dbg(&drvdata->csdev->dev,
> + "CRC mismatch in tmc crash tracedata\n");
> + return false;
> + }
> + /* Check for valid metadata */
> + if (!mdata->valid) {
minor nit: This could be checked right after the VERSION and we verify
the CRC anyway later and thus could skip all the CRC calculations if
!valid.
> + dev_dbg(&drvdata->csdev->dev,
> + "Data invalid in tmc crash metadata\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +int tmc_read_prepare_crashdata(struct tmc_drvdata *drvdata)
> +{
> + int ret = 0;
> + unsigned long flags;
> + struct tmc_crash_metadata *mdata;
> + struct coresight_device *csdev = drvdata->csdev;
> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> + if (!is_tmc_crashdata_valid(drvdata)) {
> + ret = -ENXIO;
> + goto out;
> + }
> +
> + mdata = drvdata->crash_mdata.vaddr;
> + /*
> + * Buffer address given by metadata for retrieval of trace data
> + * from previous boot is expected to be same as the reserved
> + * trace buffer memory region provided through DTS
> + */
> + if (drvdata->resrv_buf.paddr != mdata->trace_paddr) {
> + dev_dbg(&csdev->dev, "Trace buffer address of previous boot invalid\n");
Couldn't this be made part of the "is_tmc_crashdata_valid()" and not
repeated everytime we do the read ? Surely, this can't change after
boot.
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + /* Sink specific crashdata mode preparation */
> + ret = crashdata_ops(csdev)->prepare(csdev);
> + if (ret)
> + goto out;
> +
> + if (mdata->sts & 0x1)
> + coresight_insert_barrier_packet(drvdata->buf);
> +
> + drvdata->reading = true;
Why are we dealing with drvdata->reading ? That is supposed to be only
for the normal trace reading ?
> +out:
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> + return ret;
> +}
> +
> +int tmc_read_unprepare_crashdata(struct tmc_drvdata *drvdata)
> +{
> + int ret;
> + unsigned long flags;
> + struct coresight_device *csdev = drvdata->csdev;
> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> + /* Sink specific crashdata mode preparation */
> + ret = crashdata_ops(csdev)->unprepare(csdev);
> +
> + drvdata->reading = false;
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +
> + return ret;
> +}
> +
> +static inline ssize_t tmc_get_resvbuf_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + s64 offset;
> + ssize_t actual = len;
> + struct tmc_resrv_buf *rbuf = &drvdata->resrv_buf;
> +
> + if (pos + actual > rbuf->len)
> + actual = rbuf->len - pos;
> + if (actual <= 0)
> + return actual;
return 0 ? Because, we went beyond the file position, not because there
was an error. So, that it doesn't look like we are suppressing an ERROR ?
> +
> + /* Compute the offset from which we read the data */
> + offset = rbuf->offset + pos;
> + if (offset >= rbuf->size)
> + offset -= rbuf->size;
> +
> + /* Adjust the length to limit this transaction to end of buffer */
> + actual = (actual < (rbuf->size - offset)) ?
> + actual : rbuf->size - offset;
> +
> + *bufpp = (char *)rbuf->vaddr + offset;
> +
> + return actual;
> +}
> +
> static int tmc_read_prepare(struct tmc_drvdata *drvdata)
> {
> int ret = 0;
> @@ -224,6 +343,70 @@ static const struct file_operations tmc_fops = {
> .llseek = no_llseek,
> };
>
> +static int tmc_crashdata_open(struct inode *inode, struct file *file)
> +{
> + int ret;
> + struct tmc_drvdata *drvdata = container_of(file->private_data,
> + struct tmc_drvdata,
> + crashdev);
> +
> + ret = tmc_read_prepare_crashdata(drvdata);
I don't see the point of this "prepare" and unprepare callbacks, as they
can be made generic by populating the mdata->rrp,rwp fields accordingly ?
i.e., while populating the mdata-> fields, for ETR, do what you do now.
For ETF you could :
mdata->rrp = 0;
mdata->dba = 0;
mdata->rwp = drvdata->len;
mdata->size = drvdata->len >> 2;
mdata->sts = TMC_STS_FULL;
> + if (ret)
> + return ret;
> +
> + nonseekable_open(inode, file);
> +
> + dev_dbg(&drvdata->csdev->dev, "%s: successfully opened\n", __func__);
> + return 0;
> +}
> +
> +static ssize_t tmc_crashdata_read(struct file *file, char __user *data,
> + size_t len, loff_t *ppos)
> +{
> + char *bufp;
> + ssize_t actual;
> + struct tmc_drvdata *drvdata = container_of(file->private_data,
> + struct tmc_drvdata,
> + crashdev);
> +
> + actual = tmc_get_resvbuf_trace(drvdata, *ppos, len, &bufp);
> + if (actual <= 0)
> + return 0;
> +
> + if (copy_to_user(data, bufp, actual)) {
> + dev_dbg(&drvdata->csdev->dev,
> + "%s: copy_to_user failed\n", __func__);
> + return -EFAULT;
> + }
> +
> + *ppos += actual;
> + dev_dbg(&drvdata->csdev->dev, "%zu bytes copied\n", actual);
> +
> + return actual;
> +
> +}
> +
> +static int tmc_crashdata_release(struct inode *inode, struct file *file)
> +{
> + int ret = 0;
> + struct tmc_drvdata *drvdata = container_of(file->private_data,
> + struct tmc_drvdata,
> + crashdev);
> +
> + ret = tmc_read_unprepare_crashdata(drvdata);
> +
> + dev_dbg(&drvdata->csdev->dev, "%s: released\n", __func__);
> + return ret;
> +}
> +
> +static const struct file_operations tmc_crashdata_fops = {
> + .owner = THIS_MODULE,
> + .open = tmc_crashdata_open,
> + .read = tmc_crashdata_read,
> + .release = tmc_crashdata_release,
> + .llseek = no_llseek,
> +};
> +
> static enum tmc_mem_intf_width tmc_get_memwidth(u32 devid)
> {
> enum tmc_mem_intf_width memwidth;
> @@ -533,6 +716,20 @@ static u32 tmc_etr_get_max_burst_size(struct device *dev)
> return burst_size;
> }
>
> +static void register_crash_dev_interface(struct tmc_drvdata *drvdata,
> + const char *name)
> +{
> + drvdata->crashdev.name =
> + devm_kasprintf(&drvdata->csdev->dev, GFP_KERNEL, "%s_%s", "crash", name);
> + drvdata->crashdev.minor = MISC_DYNAMIC_MINOR;
> + drvdata->crashdev.fops = &tmc_crashdata_fops;
> + if (misc_register(&drvdata->crashdev)) {
> + dev_dbg(&drvdata->csdev->dev,
> + "Failed to setup user interface for crashdata\n");
> + drvdata->crashdev.fops = NULL;
> + }
> +}
> +
> static int __tmc_probe(struct device *dev, struct resource *res)
> {
> int ret = 0;
> @@ -633,8 +830,13 @@ static int __tmc_probe(struct device *dev, struct resource *res)
> drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;
> drvdata->miscdev.fops = &tmc_fops;
> ret = misc_register(&drvdata->miscdev);
> - if (ret)
> + if (ret) {
> coresight_unregister(drvdata->csdev);
> + goto out;
> + }
> +
> + if (is_tmc_crashdata_valid(drvdata))
> + register_crash_dev_interface(drvdata, desc.name);
> out:
> return ret;
> }
> @@ -688,6 +890,8 @@ static void __tmc_remove(struct device *dev)
> * handler to this device is closed.
> */
> misc_deregister(&drvdata->miscdev);
> + if (drvdata->crashdev.fops)
> + misc_deregister(&drvdata->crashdev);
> coresight_unregister(drvdata->csdev);
> }
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index d77ec9307e98..2b4639a1def2 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -662,6 +662,36 @@ static int tmc_panic_sync_etf(struct coresight_device *csdev)
> return 0;
> }
>
> +static int tmc_etb_prepare_crashdata(struct coresight_device *csdev)
> +{
> + unsigned long size;
> + struct tmc_resrv_buf *rbuf;
> + struct tmc_crash_metadata *mdata;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + rbuf = &drvdata->resrv_buf;
> + mdata = drvdata->crash_mdata.vaddr;
> + size = mdata->size << 2;
> +
> + rbuf->len = size;
> + rbuf->offset = 0;
> + rbuf->full = 0;
> +
> + return 0;
> +}
> +
> +static int tmc_etb_unprepare_crashdata(struct coresight_device *csdev)
> +{
> + struct tmc_resrv_buf *rbuf;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + rbuf = &drvdata->resrv_buf;
> + /* Reset valid length */
> + rbuf->len = 0;
> +
> + return 0;
> +}
> +
> static const struct coresight_ops_sink tmc_etf_sink_ops = {
> .enable = tmc_enable_etf_sink,
> .disable = tmc_disable_etf_sink,
> @@ -679,6 +709,11 @@ static const struct coresight_ops_panic tmc_etf_sync_ops = {
> .sync = tmc_panic_sync_etf,
> };
>
> +static const struct coresight_ops_crashdata tmc_etf_crashdata_ops = {
> + .prepare = tmc_etb_prepare_crashdata,
> + .unprepare = tmc_etb_unprepare_crashdata,
> +};
> +
> const struct coresight_ops tmc_etb_cs_ops = {
> .sink_ops = &tmc_etf_sink_ops,
> };
> @@ -687,6 +722,7 @@ const struct coresight_ops tmc_etf_cs_ops = {
> .sink_ops = &tmc_etf_sink_ops,
> .link_ops = &tmc_etf_link_ops,
> .panic_ops = &tmc_etf_sync_ops,
> + .crashdata_ops = &tmc_etf_crashdata_ops,
> };
>
> int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 8228d7aaa361..7688b8d70ced 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1887,6 +1887,55 @@ static int tmc_panic_sync_etr(struct coresight_device *csdev)
> return 0;
> }
>
> +static int tmc_etr_prepare_crashdata(struct coresight_device *csdev)
> +{
> + u32 status;
> + u64 rrp, rwp, dba;
> + struct tmc_resrv_buf *rbuf;
> + struct tmc_crash_metadata *mdata;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + rbuf = &drvdata->resrv_buf;
> + mdata = drvdata->crash_mdata.vaddr;
> +
> + rrp = mdata->rrp;
> + rwp = mdata->rwp;
> + dba = mdata->dba;
> + status = mdata->sts;
> +
> + rbuf->full = !!(status & TMC_STS_FULL);
> +
> + /* Sync the buffer pointers */
> + rbuf->offset = rrp - dba;
> + if (rbuf->full)
> + rbuf->len = rbuf->size;
Why are we nto using mdata->size << 2 ? What if the "reserved buf" size
was changes by the firmware, keeping the base same ?
> + else
> + rbuf->len = rwp - rrp;
We don't seem to be using "full" anywhere else other than this routine.
So we could simply drop it ?
As I mentioned above, I don't see why the "rbuf" cannot be constructed
from a generic "metadata" (provided we fix the TMC-ETF mdata storage)
and drop these ETF/ETR specific prepare/unprepare callbacks.
> +
> + /* Additional sanity checks for validating metadata */
> + if ((rbuf->offset > rbuf->size) ||
> + (rbuf->len > rbuf->size)) {
> + dev_dbg(&drvdata->csdev->dev,
> + "Offset and length invalid in tmc crash metadata\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int tmc_etr_unprepare_crashdata(struct coresight_device *csdev)
> +{
> + struct tmc_resrv_buf *rbuf;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + rbuf = &drvdata->resrv_buf;
> +
> + /* Reset valid length */
> + rbuf->len = 0;
> +
> + return 0;
> +}
> +
> static const struct coresight_ops_sink tmc_etr_sink_ops = {
> .enable = tmc_enable_etr_sink,
> .disable = tmc_disable_etr_sink,
> @@ -1899,9 +1948,15 @@ static const struct coresight_ops_panic tmc_etr_sync_ops = {
> .sync = tmc_panic_sync_etr,
> };
>
> +static const struct coresight_ops_crashdata tmc_etr_crashdata_ops = {
> + .prepare = tmc_etr_prepare_crashdata,
> + .unprepare = tmc_etr_unprepare_crashdata,
> +};
> +
> const struct coresight_ops tmc_etr_cs_ops = {
> .sink_ops = &tmc_etr_sink_ops,
> .panic_ops = &tmc_etr_sync_ops,
> + .crashdata_ops = &tmc_etr_crashdata_ops,
> };
>
> int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
> @@ -1934,6 +1989,14 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
> __tmc_etr_disable_hw(drvdata);
>
> drvdata->reading = true;
> +
> + /*
> + * The only other place we mark the metadata invalid is during
> + * panic handler. Normally this won't race with panic handler,
> + * as all cpus would be stopped before running panic handler.
> + */
> + if (drvdata->etr_mode == ETR_MODE_RESRV)
> + tmc_crashdata_set_invalid(drvdata);
> out:
> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 75e504e51956..a6daa35c7cc1 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -195,11 +195,17 @@ struct etr_buf {
> * @paddr : Start address of reserved memory region.
> * @vaddr : Corresponding CPU virtual address.
> * @size : Size of reserved memory region.
> + * @full : Trace data overflow
> + * @offset : Offset of the trace data in the buffer for consumption.
> + * @len : Available trace data @buf (may round up to the beginning).
super minor nit: extra TAB
> */
> struct tmc_resrv_buf {
> phys_addr_t paddr;
> void *vaddr;
> size_t size;
> + bool full;
As mentioned above, drop it ^^
> + unsigned long offset;
> + s64 len;
> };
>
> /**
> @@ -208,6 +214,8 @@ struct tmc_resrv_buf {
> * @base: memory mapped base address for this component.
> * @csdev: component vitals needed by the framework.
> * @miscdev: specifics to handle "/dev/xyz.tmc" entry.
> + * @crashdev: specifics to handle "/dev/crash_tmc_xyz" entry for reading
> + * crash tracedata.
> * @spinlock: only one at a time pls.
> * @pid: Process ID of the process that owns the session that is using
> * this component. For example this would be the pid of the Perf
> @@ -227,7 +235,10 @@ struct tmc_resrv_buf {
> * @idr_mutex: Access serialisation for idr.
> * @sysfs_buf: SYSFS buffer for ETR.
> * @perf_buf: PERF buffer for ETR.
> - * @resrv_buf: Used by ETR as hardware trace buffer and for trace data
> + * @sysfs_crash_buf: Sysfs crashdata buffer for ETR. This is a special purpose
> + * buffer that is used only for mapping the trace buffer from
> + * previous crash and not for capturing trace.
This looks like a left over from the previous version. Please drop.
> + * @resrv_buf: Used by ETR as hardware trace buffer and for trace data
> * retention (after crash) only when ETR_MODE_RESRV buffer
> * mode is enabled. Used by ETF for trace data retention
> * (after crash) by default.
> @@ -239,6 +250,7 @@ struct tmc_drvdata {
> void __iomem *base;
> struct coresight_device *csdev;
> struct miscdevice miscdev;
> + struct miscdevice crashdev;
> spinlock_t spinlock;
> pid_t pid;
> bool reading;
> @@ -309,6 +321,8 @@ void tmc_flush_and_stop(struct tmc_drvdata *drvdata);
> void tmc_enable_hw(struct tmc_drvdata *drvdata);
> void tmc_disable_hw(struct tmc_drvdata *drvdata);
> u32 tmc_get_memwidth_mask(struct tmc_drvdata *drvdata);
> +int tmc_read_prepare_crashdata(struct tmc_drvdata *drvdata);
> +int tmc_read_unprepare_crashdata(struct tmc_drvdata *drvdata);
>
> /* ETB/ETF functions */
> int tmc_read_prepare_etb(struct tmc_drvdata *drvdata);
> @@ -371,6 +385,8 @@ void tmc_sg_table_sync_data_range(struct tmc_sg_table *table,
> u64 offset, u64 size);
> ssize_t tmc_sg_table_get_data(struct tmc_sg_table *sg_table,
> u64 offset, size_t len, char **bufpp);
> +
> +bool is_tmc_crashdata_valid(struct tmc_drvdata *drvdata);
> static inline unsigned long
> tmc_sg_table_buf_size(struct tmc_sg_table *sg_table)
> {
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index 2e63f7614551..f04e40828885 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -336,6 +336,7 @@ enum cs_mode {
> #define helper_ops(csdev) csdev->ops->helper_ops
> #define ect_ops(csdev) csdev->ops->ect_ops
> #define panic_ops(csdev) csdev->ops->panic_ops
> +#define crashdata_ops(csdev) csdev->ops->crashdata_ops
>
> /**
> * struct coresight_ops_sink - basic operations for a sink
> @@ -415,12 +416,23 @@ struct coresight_ops_panic {
> int (*sync)(struct coresight_device *csdev);
> };
>
> +/**
> + * struct coresight_ops_crashdata - Generic device ops for crashdata mode
> + *
> + * @prepare : Preparation for reading crashdata mode
> + */
> +struct coresight_ops_crashdata {
> + int (*prepare)(struct coresight_device *csdev);
> + int (*unprepare)(struct coresight_device *csdev);
> +};
> +
Drop these please ^^
> struct coresight_ops {
> const struct coresight_ops_sink *sink_ops;
> const struct coresight_ops_link *link_ops;
> const struct coresight_ops_source *source_ops;
> const struct coresight_ops_helper *helper_ops;
> const struct coresight_ops_panic *panic_ops;
> + const struct coresight_ops_crashdata *crashdata_ops;
> };
>
> static inline u32 csdev_access_relaxed_read32(struct csdev_access *csa,
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