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

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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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