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

From: Linu Cherian
Date: Mon Jun 10 2024 - 02:19:22 EST

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Hi Suzuki,

> -----Original Message-----
> From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Sent: Friday, June 7, 2024 9:28 PM
> To: Linu Cherian <lcherian@xxxxxxxxxxx>; mike.leach@xxxxxxxxxx;
> james.clark@xxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; coresight@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> krzysztof.kozlowski+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Sunil Kovvuri Goutham
> <sgoutham@xxxxxxxxxxx>; George Cherian <gcherian@xxxxxxxxxxx>; Anil
> Kumar Reddy H <areddy3@xxxxxxxxxxx>
> Subject: [EXTERNAL] Re: [PATCH v9 2/7] coresight: tmc-etr: Add support to
> use reserved trace memory
>
> Prioritize security for external emails: Confirm sender and content safety
> before clicking links or opening attachments
>
> ----------------------------------------------------------------------
> Hi Linu
>
> On 05/06/2024 09:17, Linu Cherian wrote:
> > Add support to use reserved memory for coresight ETR trace buffer.
> >
> > Introduce a new ETR buffer mode called ETR_MODE_RESRV, which
> becomes
> > available when ETR device tree node is supplied with a valid reserved
> > memory region.
> >
> > ETR_MODE_RESRV can be selected only by explicit user request.
> >
> > $ echo resrv
> >/sys/bus/coresight/devices/tmc_etr<N>/buf_mode_preferred
> >
> > Signed-off-by: Anil Kumar Reddy <areddy3@xxxxxxxxxxx>
> > Signed-off-by: Linu Cherian <lcherian@xxxxxxxxxxx>
> > Reviewed-by: James Clark <james.clark@xxxxxxx>
>
> Some minor comments below.
>
>
> > ---
> > Changelog from v8:
> > Added Reviewed-by tag.
> >
> > .../hwtracing/coresight/coresight-tmc-core.c | 47 +++++++++++
> > .../hwtracing/coresight/coresight-tmc-etr.c | 79 +++++++++++++++++++
> > drivers/hwtracing/coresight/coresight-tmc.h | 27 +++++++
> > 3 files changed, 153 insertions(+)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c
> > b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > index 741ce1748e75..6beb69d74d0a 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > @@ -23,6 +23,7 @@
> > #include <linux/spinlock.h>
> > #include <linux/pm_runtime.h>
> > #include <linux/of.h>
> > +#include <linux/of_address.h>
> > #include <linux/coresight.h>
> > #include <linux/amba/bus.h>
> > #include <linux/platform_device.h>
> > @@ -400,6 +401,50 @@ static inline bool
> > tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)
> >
> > static const struct amba_id tmc_ids[];
> >
> > +static struct device_node *tmc_get_region_byname(struct device_node
> *node,
> > + char *name)
> > +{
> > + int index;
> > +
> > + index = of_property_match_string(node, "memory-region-names",
> name);
> > + if (index < 0)
> > + return ERR_PTR(-ENODEV);
> > +
> > + return of_parse_phandle(node, "memory-region", index); }
> > +
> > +static void tmc_get_reserved_region(struct device *parent) {
> > + struct tmc_drvdata *drvdata = dev_get_drvdata(parent);
> > + struct device_node *node;
> > + struct resource res;
> > + int rc;
> > +
> > + node = tmc_get_region_byname(parent->of_node, "tracedata");
> > + if (IS_ERR_OR_NULL(node)) {
> > + dev_dbg(parent, "No reserved trace buffer specified\n");
> > + return;
> > + }
> > +
> > + rc = of_address_to_resource(node, 0, &res);
>
> This sequence is repeated again in the metadat area, where :
>
> 1. We get region by name.
> 2. Read the resource details.
>
> Could we not make "the helper" do both and move the "of_node_put()"
> inside the helper ?
>

Ack.

> static int of_tmc_get_reserved_resource_by_name(struct device *dev,
> const char *name,
> struct resource *res)
> {
>
> > + int index, rc = -ENODEV;
> > + struct device_node *node;
>
> if (!is_of_node(dev_fwnode(dev->fwnode)))
> return -ENODEV;
> > +
> > + index = of_property_match_string(dev->of_node,
> "memory-region-names", name);
> > + if (index < 0)
> > + return rc;
> > +
> > + node = of_parse_phandle(node, "memory-region", index);
> if (!node)
> return rc;
>
> if (!of_address_to_resource(node, 0, res) &&
> res->start != 0 && resource_size(res) != 0)
> rc = 0;
> of_node_put(node);
>
> return rc;
> }
>
>
> > + of_node_put(node);
> > + if (rc || res.start == 0 || resource_size(&res) == 0) {
> > + dev_err(parent, "Reserved trace buffer memory is
> invalid\n");
> > + return;
> > + }
>
> and the caller does :
>
> if (of_tmc_get_reserved_area_by_name(parent, "tracedata", &res))
> return;
>

Okay.

> > +
> > + drvdata->crash_tbuf.vaddr = memremap(res.start,
> > + resource_size(&res),
> > + MEMREMAP_WC);
> > + if (IS_ERR_OR_NULL(drvdata->crash_tbuf.vaddr)) {
> > + dev_err(parent, "Reserved trace buffer mapping failed\n");
> > + return;
> > + }
> > +
> > + drvdata->crash_tbuf.paddr = res.start;
> > + drvdata->crash_tbuf.size = resource_size(&res); }
> > +
> > /* Detect and initialise the capabilities of a TMC ETR */
> > static int tmc_etr_setup_caps(struct device *parent, u32 devid,
> > struct csdev_access *access) @@ -510,6 +555,8
> @@ static int
> > __tmc_probe(struct device *dev, struct resource *res)
> > drvdata->size = readl_relaxed(drvdata->base + TMC_RSZ) *
> 4;
> > }
> >
> > + tmc_get_reserved_region(dev);
> > +
> > desc.dev = dev;
> >
> > switch (drvdata->config_type) {
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > index e75428fa1592..041c428dd7cd 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > @@ -30,6 +30,7 @@ struct etr_buf_hw {
> > bool has_iommu;
> > bool has_etr_sg;
> > bool has_catu;
> > + bool has_resrv;
> > };
> >
> > /*
> > @@ -694,6 +695,75 @@ static const struct etr_buf_operations
> etr_flat_buf_ops = {
> > .get_data = tmc_etr_get_data_flat_buf,
> > };
> >
> > +/*
> > + * tmc_etr_alloc_resrv_buf: Allocate a contiguous DMA buffer from
> reserved region.
> > + */
> > +static int tmc_etr_alloc_resrv_buf(struct tmc_drvdata *drvdata,
> > + struct etr_buf *etr_buf, int node,
> > + void **pages)
> > +{
> > + struct etr_flat_buf *resrv_buf;
> > + struct device *real_dev = drvdata->csdev->dev.parent;
> > +
> > + /* We cannot reuse existing pages for resrv buf */
> > + if (pages)
> > + return -EINVAL;
> > +
> > + resrv_buf = kzalloc(sizeof(*resrv_buf), GFP_KERNEL);
> > + if (!resrv_buf)
> > + return -ENOMEM;
> > +
> > + resrv_buf->daddr = dma_map_resource(real_dev, drvdata-
> >crash_tbuf.paddr,
> > + drvdata->crash_tbuf.size,
> > + DMA_FROM_DEVICE, 0);
> > + if (dma_mapping_error(real_dev, resrv_buf->daddr)) {
> > + dev_err(real_dev, "failed to map source buffer address\n");
> > + kfree(resrv_buf);
> > + return -ENOMEM;
> > + }
> > +
> > + resrv_buf->vaddr = drvdata->crash_tbuf.vaddr;
> > + resrv_buf->size = etr_buf->size = drvdata->crash_tbuf.size;
> > + resrv_buf->dev = &drvdata->csdev->dev;
> > + etr_buf->hwaddr = resrv_buf->daddr;
> > + etr_buf->mode = ETR_MODE_RESRV;
> > + etr_buf->private = resrv_buf;
> > + return 0;
> > +}
> > +
> > +static void tmc_etr_free_resrv_buf(struct etr_buf *etr_buf) {
> > + struct etr_flat_buf *resrv_buf = etr_buf->private;
> > +
> > + if (resrv_buf && resrv_buf->daddr) {
>
>
> > + struct device *real_dev = resrv_buf->dev->parent;
> > +
> > + dma_unmap_resource(real_dev, resrv_buf->daddr,
> > + resrv_buf->size, DMA_FROM_DEVICE, 0);
> > + }
> > + kfree(resrv_buf);
> > +}
> > +
> > +static void tmc_etr_sync_resrv_buf(struct etr_buf *etr_buf, u64 rrp,
> > +u64 rwp) {
> > + /*
> > + * Adjust the buffer to point to the beginning of the trace data
> > + * and update the available trace data.
> > + */
> > + etr_buf->offset = rrp - etr_buf->hwaddr;
> > + if (etr_buf->full)
> > + etr_buf->len = etr_buf->size;
> > + else
> > + etr_buf->len = rwp - rrp;
> > +}
> > +
> > +static const struct etr_buf_operations etr_resrv_buf_ops = {
> > + .alloc = tmc_etr_alloc_resrv_buf,
> > + .free = tmc_etr_free_resrv_buf,
> > + .sync = tmc_etr_sync_resrv_buf,
> > + .get_data = tmc_etr_get_data_flat_buf, };
> > +
> > /*
> > * tmc_etr_alloc_sg_buf: Allocate an SG buf @etr_buf. Setup the
> parameters
> > * appropriately.
> > @@ -800,6 +870,7 @@ static const struct etr_buf_operations
> *etr_buf_ops[] = {
> > [ETR_MODE_FLAT] = &etr_flat_buf_ops,
> > [ETR_MODE_ETR_SG] = &etr_sg_buf_ops,
> > [ETR_MODE_CATU] = NULL,
> > + [ETR_MODE_RESRV] = &etr_resrv_buf_ops
> > };
> >
> > void tmc_etr_set_catu_ops(const struct etr_buf_operations *catu) @@
> > -825,6 +896,7 @@ static inline int tmc_etr_mode_alloc_buf(int mode,
> > case ETR_MODE_FLAT:
> > case ETR_MODE_ETR_SG:
> > case ETR_MODE_CATU:
> > + case ETR_MODE_RESRV:
> > if (etr_buf_ops[mode] && etr_buf_ops[mode]->alloc)
> > rc = etr_buf_ops[mode]->alloc(drvdata, etr_buf,
> > node, pages);
> > @@ -843,6 +915,7 @@ static void get_etr_buf_hw(struct device *dev,
> struct etr_buf_hw *buf_hw)
> > 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);
> > + buf_hw->has_resrv = is_tmc_reserved_region_valid(dev->parent);
>
> Minor nit: In line with the other helpers, please could we rename this to :
>
> tmc_has_reserved_buffer(drvdata) ?
>
> We already have access to drvdata and we can pass that directly instead of
> passing the dev->parent and then fetch drvdata again.
>

Ack.

> > }
> >
> > static bool etr_can_use_flat_mode(struct etr_buf_hw *buf_hw, ssize_t
> > etr_buf_size) @@ -1830,6 +1903,7 @@ static const char *const
> buf_modes_str[] = {
> > [ETR_MODE_FLAT] = "flat",
> > [ETR_MODE_ETR_SG] = "tmc-sg",
> > [ETR_MODE_CATU] = "catu",
> > + [ETR_MODE_RESRV] = "resrv",
> > [ETR_MODE_AUTO] = "auto",
> > };
> >
> > @@ -1848,6 +1922,9 @@ static ssize_t buf_modes_available_show(struct
> device *dev,
> > if (buf_hw.has_catu)
> > size += sysfs_emit_at(buf, size, "%s ",
> > buf_modes_str[ETR_MODE_CATU]);
> >
> > + if (buf_hw.has_resrv)
> > + size += sysfs_emit_at(buf, size, "%s ",
> > +buf_modes_str[ETR_MODE_RESRV]);
> > +
> > size += sysfs_emit_at(buf, size, "\n");
> > return size;
> > }
> > @@ -1875,6 +1952,8 @@ static ssize_t buf_mode_preferred_store(struct
> device *dev,
> > 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_RESRV]) &&
> buf_hw.has_resrv)
> > + drvdata->etr_mode = ETR_MODE_RESRV;
> > else if (sysfs_streq(buf, buf_modes_str[ETR_MODE_AUTO]))
> > drvdata->etr_mode = ETR_MODE_AUTO;
> > else
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc.h
> > b/drivers/hwtracing/coresight/coresight-tmc.h
> > index c77763b49de0..c23dc9917ab9 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc.h
> > +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> > @@ -135,6 +135,7 @@ enum etr_mode {
> > ETR_MODE_FLAT, /* Uses contiguous flat buffer */
> > ETR_MODE_ETR_SG, /* Uses in-built TMC ETR SG mechanism */
> > ETR_MODE_CATU, /* Use SG mechanism in CATU */
> > + ETR_MODE_RESRV, /* Use reserved region contiguous
> buffer */
> > ETR_MODE_AUTO, /* Use the default mechanism */
> > };
> >
> > @@ -164,6 +165,17 @@ struct etr_buf {
> > void *private;
> > };
> >
> > +/**
> > + * @paddr : Start address of reserved memory region.
> > + * @vaddr : Corresponding CPU virtual address.
> > + * @size : Size of reserved memory region.
> > + */
> > +struct tmc_resrv_buf {
> > + phys_addr_t paddr;
> > + void *vaddr;
> > + size_t size;
> > +};
> > +
> > /**
> > * struct tmc_drvdata - specifics associated to an TMC component
> > * @pclk: APB clock if present, otherwise NULL
> > @@ -188,6 +200,10 @@ struct etr_buf {
> > * @idr_mutex: Access serialisation for idr.
> > * @sysfs_buf: SYSFS buffer for ETR.
> > * @perf_buf: PERF buffer for ETR.
> > + * @crash_tbuf: Used by ETR as hardware trace buffer and for trace
> data
> > + * retention (after crash) only when ETR_MODE_RESRV buffer
> > + * mode is enabled. Used by ETF for trace data retention
> > + * (after crash) by default.
>
> Minor nit: This need not be called crash_tbuf, could instead be resrv_buf as
> we use it everywhere.
>

Ack.

> Suzuki
>
>
> > */
> > struct tmc_drvdata {
> > struct clk *pclk;
> > @@ -213,6 +229,7 @@ struct tmc_drvdata {
> > struct mutex idr_mutex;
> > struct etr_buf *sysfs_buf;
> > struct etr_buf *perf_buf;
> > + struct tmc_resrv_buf crash_tbuf;
> > };
> >
> > struct etr_buf_operations {
> > @@ -330,6 +347,16 @@ tmc_sg_table_buf_size(struct tmc_sg_table
> *sg_table)
> > return (unsigned long)sg_table->data_pages.nr_pages <<
> PAGE_SHIFT;
> > }
> >
> > +static inline bool is_tmc_reserved_region_valid(struct device *dev) {
> > + struct tmc_drvdata *drvdata = dev_get_drvdata(dev);
> > +
> > + if (drvdata->crash_tbuf.paddr &&
> > + drvdata->crash_tbuf.size)
> > + return true;
> > + return false;
> > +}
> > +
> > struct coresight_device *tmc_etr_get_catu_device(struct tmc_drvdata
> > *drvdata);
> >
> > void tmc_etr_set_catu_ops(const struct etr_buf_operations *catu);

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