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Message-ID: <9422ba89-a6ba-4168-98a1-6d4275698430@gmail.com>
Date: Tue, 7 Oct 2025 00:49:42 -0700
From: Bo Gan <ganboing@...il.com>
To: Anup Patel <apatel@...tanamicro.com>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Greg KH <gregkh@...uxfoundation.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Ian Rogers <irogers@...gle.com>
Cc: Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org,
Alexandre Ghiti <alex@...ti.fr>, Atish Patra <atish.patra@...ux.dev>,
Peter Zijlstra <peterz@...radead.org>, Anup Patel <anup@...infault.org>,
Adrian Hunter <adrian.hunter@...el.com>, linux-kernel@...r.kernel.org,
Mayuresh Chitale <mchitale@...tanamicro.com>, Ingo Molnar
<mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
Mayuresh Chitale <mchitale@...il.com>, Namhyung Kim <namhyung@...nel.org>,
linux-riscv@...ts.infradead.org, Andrew Jones <ajones@...tanamicro.com>,
Liang Kan <kan.liang@...ux.intel.com>
Subject: Re: [PATCH 07/11] rvtrace: Add trace ramsink driver
On 10/1/25 23:07, Anup Patel wrote:
> From: Mayuresh Chitale <mchitale@...tanamicro.com>
>
> Add initial implementation of RISC-V trace ramsink driver. The ramsink
> is defined in the RISC-V Trace Control Interface specification.
>
> Co-developed-by: Anup Patel <apatel@...tanamicro.com>
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> Signed-off-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> ---
> drivers/hwtracing/rvtrace/Kconfig | 8 +
> drivers/hwtracing/rvtrace/Makefile | 1 +
> drivers/hwtracing/rvtrace/rvtrace-ramsink.c | 198 ++++++++++++++++++++
> 3 files changed, 207 insertions(+)
> create mode 100644 drivers/hwtracing/rvtrace/rvtrace-ramsink.c
>
> diff --git a/drivers/hwtracing/rvtrace/Kconfig b/drivers/hwtracing/rvtrace/Kconfig
> index ba35c05f3f54..aef7e9989165 100644
> --- a/drivers/hwtracing/rvtrace/Kconfig
> +++ b/drivers/hwtracing/rvtrace/Kconfig
> @@ -21,3 +21,11 @@ config RVTRACE_ENCODER
> default y
> help
> This driver provides support for RISC-V Trace Encoder component.
> +
> +config RVTRACE_RAMSINK
> + tristate "RISC-V Trace Ramsink driver"
> + depends on RVTRACE
> + default y
> + help
> + This driver provides support for Risc-V E-Trace Ramsink
> + component.
> diff --git a/drivers/hwtracing/rvtrace/Makefile b/drivers/hwtracing/rvtrace/Makefile
> index f320693a1fc5..122e575da9fb 100644
> --- a/drivers/hwtracing/rvtrace/Makefile
> +++ b/drivers/hwtracing/rvtrace/Makefile
> @@ -3,3 +3,4 @@
> obj-$(CONFIG_RVTRACE) += rvtrace.o
> rvtrace-y := rvtrace-core.o rvtrace-platform.o
> obj-$(CONFIG_RVTRACE_ENCODER) += rvtrace-encoder.o
> +obj-$(CONFIG_RVTRACE_RAMSINK) += rvtrace-ramsink.o
> diff --git a/drivers/hwtracing/rvtrace/rvtrace-ramsink.c b/drivers/hwtracing/rvtrace/rvtrace-ramsink.c
> new file mode 100644
> index 000000000000..7bd0cf1e4dfd
> --- /dev/null
> +++ b/drivers/hwtracing/rvtrace/rvtrace-ramsink.c
> @@ -0,0 +1,198 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2025 Ventana Micro Systems Inc.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/rvtrace.h>
> +#include <linux/types.h>
> +#include <linux/sizes.h>
> +
> +#define RVTRACE_RAMSINK_STARTLOW_OFF 0x010
> +#define RVTRACE_RAMSINK_STARTHIGH_OFF 0x014
> +#define RVTRACE_RAMSINK_LIMITLOW_OFF 0x018
> +#define RVTRACE_RAMSINK_LIMITHIGH_OFF 0x01c
> +#define RVTRACE_RAMSINK_WPLOW_OFF 0x020
> +#define RVTRACE_RAMSINK_WPHIGH_OFF 0x024
> +#define RVTRACE_RAMSINK_RPLOW_OFF 0x028
> +#define RVTRACE_RAMSINK_RPHIGH_OFF 0x02c
> +
> +struct rvtrace_ramsink_priv {
> + size_t size;
> + void *va;
> + dma_addr_t start;
> + dma_addr_t end;
> + /* WP from prev iteration */
> + dma_addr_t prev_head;
> +};
> +
> +struct trace_buf {
> + void *base;
> + size_t size;
> + int cur, len;
> +};
> +
> +static void tbuf_to_pbuf_copy(struct trace_buf *src, struct trace_buf *dst)
> +{
> + int bytes_dst, bytes_src, bytes;
> + void *dst_addr, *src_addr;
> +
> + while (src->size) {
> + src_addr = src->base + src->cur;
> + dst_addr = dst->base + dst->cur;
> +
> + if (dst->len - dst->cur < src->size)
> + bytes_dst = dst->len - dst->cur;
> + else
> + bytes_dst = src->size;
> + if (src->len - src->cur < src->size)
> + bytes_src = src->len - src->cur;
> + else
> + bytes_src = src->size;
> + bytes = bytes_dst < bytes_src ? bytes_dst : bytes_src;
> + memcpy(dst_addr, src_addr, bytes);
> + dst->cur = (dst->cur + bytes) % dst->len;
> + src->cur = (src->cur + bytes) % src->len;
> + src->size -= bytes;
> + }
> +}
> +
> +static size_t rvtrace_ramsink_copyto_auxbuf(struct rvtrace_component *comp,
> + struct rvtrace_perf_auxbuf *buf)
> +{
> + struct rvtrace_ramsink_priv *priv = dev_get_drvdata(&comp->dev);
> + struct trace_buf src, dst;
> + u32 wp_low, wp_high;
> + u64 buf_cur_head;
> + size_t size;
> +
> + wp_low = rvtrace_read32(comp->pdata, RVTRACE_RAMSINK_WPLOW_OFF);
> + wp_high = rvtrace_read32(comp->pdata, RVTRACE_RAMSINK_WPHIGH_OFF);
> + buf_cur_head = (u64)(wp_high) << 32 | wp_low;
> +
> + if (buf_cur_head == priv->prev_head)
> + return 0;
> +
> + dst.base = buf->base;
> + dst.len = buf->length;
> + dst.cur = buf->pos;
> + dst.size = 0;
> +
> + src.base = priv->va;
> + src.len = priv->end - priv->start;
> + if (buf_cur_head > priv->prev_head) {
> + src.size = buf_cur_head - priv->prev_head;
> + } else {
> + src.size = priv->end - priv->prev_head;
> + src.size += buf_cur_head - priv->start;
> + }
> +
> + src.cur = buf_cur_head - priv->start;
> + size = src.size;
> + tbuf_to_pbuf_copy(&src, &dst);
> + buf->pos = dst.cur;
> + priv->prev_head = buf_cur_head;
> +
> + return size;
> +}
> +
> +static int rvtrace_ramsink_setup(struct rvtrace_component *comp)
> +{
> + struct rvtrace_ramsink_priv *priv;
> +
> + priv = devm_kzalloc(&comp->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> + dev_set_drvdata(&comp->dev, priv);
> +
> + priv->size = SZ_4M;
Can we make this size dynamically determined? 4M seems inadequate. This is
exceedingly so if the RAM sink is linked to a funnel, where you can have
many harts dumping traces into this sink.
> + priv->va = dma_alloc_coherent(&comp->dev, priv->size, &priv->start, GFP_KERNEL);
> + if (!priv->va)
> + return -ENOMEM;
> + priv->end = priv->start + priv->size;
> + priv->prev_head = priv->start;
> +
> + /* Setup ram sink addresses */
> + rvtrace_write32(comp->pdata, lower_32_bits(priv->start), RVTRACE_RAMSINK_STARTLOW_OFF);
> + rvtrace_write32(comp->pdata, upper_32_bits(priv->start), RVTRACE_RAMSINK_STARTHIGH_OFF);
> + rvtrace_write32(comp->pdata, lower_32_bits(priv->start), RVTRACE_RAMSINK_WPLOW_OFF);
> + rvtrace_write32(comp->pdata, upper_32_bits(priv->start), RVTRACE_RAMSINK_WPHIGH_OFF);
> + /* Limit address needs to be set to end - 4 so that HW doesn't cause an overflow. */> + rvtrace_write32(comp->pdata, lower_32_bits(priv->end - 0x4), RVTRACE_RAMSINK_LIMITLOW_OFF);
Should not hardcode 4 as the trace write width. Control Interface Spec
chapter 7.1 has the proper instruction on how to probe for this width:
"Not every value may be settable in trRamStart/Limit registers. Value
written may be trimmed (for example aligned on a particular 2^N boundary)
and a trace tool should verify values being written"
> + rvtrace_write32(comp->pdata, upper_32_bits(priv->end), RVTRACE_RAMSINK_LIMITHIGH_OFF);
> +
> + return 0;
> +}
> +
> +static void rvtrace_ramsink_cleanup(struct rvtrace_component *comp)
> +{
> + struct rvtrace_ramsink_priv *priv = dev_get_drvdata(&comp->dev);
> +
> + dma_free_coherent(&comp->dev, priv->size, priv->va, priv->start);
> +}
> +
> +static int rvtrace_ramsink_probe(struct rvtrace_component *comp)
> +{
> + int ret;
> +
> + ret = rvtrace_ramsink_setup(comp);
> + if (ret)
> + return dev_err_probe(&comp->dev, ret, "failed to setup ramsink.\n");
> +
> + ret = rvtrace_enable_component(comp);
> + if (ret)
> + return dev_err_probe(&comp->dev, ret, "failed to enable ramsink.\n");
> +
> + return ret;
> +}
> +
> +static void rvtrace_ramsink_remove(struct rvtrace_component *comp)
> +{
> + int ret;
> +
> + ret = rvtrace_disable_component(comp);
> + if (ret)
> + dev_err(&comp->dev, "failed to disable ramsink.\n");
> +
> + rvtrace_ramsink_cleanup(comp);
> +}
> +
> +static struct rvtrace_component_id rvtrace_ramsink_ids[] = {
> + { .type = RVTRACE_COMPONENT_TYPE_RAMSINK,
> + .version = rvtrace_component_mkversion(1, 0), },
> + {},
> +};
> +
> +static struct rvtrace_driver rvtrace_ramsink_driver = {
> + .id_table = rvtrace_ramsink_ids,
> + .copyto_auxbuf = rvtrace_ramsink_copyto_auxbuf,
> + .probe = rvtrace_ramsink_probe,
> + .remove = rvtrace_ramsink_remove,
> + .driver = {
> + .name = "rvtrace-ramsink",
> + },
> +};
> +
> +static int __init rvtrace_ramsink_init(void)
> +{
> + return rvtrace_register_driver(&rvtrace_ramsink_driver);
> +}
> +
> +static void __exit rvtrace_ramsink_exit(void)
> +{
> + rvtrace_unregister_driver(&rvtrace_ramsink_driver);
> +}
> +
> +module_init(rvtrace_ramsink_init);
> +module_exit(rvtrace_ramsink_exit);
> +
> +/* Module information */
> +MODULE_AUTHOR("Mayuresh Chitale <mchitale@...tanamicro.com>");
> +MODULE_DESCRIPTION("RISC-V Trace Ramsink Driver");
> +MODULE_LICENSE("GPL");
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