Re: [PATCH] stm: class: Add MIPI OST protocol support

[Jinlong Mao]

Hi Reviewers,

Could you please help to review this patch ?

Thanks
Jinlong Mao

On 2/8/2023 8:40 PM, Mao Jinlong wrote:
> Add MIPI OST protocol support for stm to format the traces.
> Framework copied from drivers/hwtracing/stm.p-sys-t.c as of
> commit d69d5e83110f ("stm class: Add MIPI SyS-T protocol
> support").
>
> Signed-off-by: Tingwei Zhang <quic_tingweiz@xxxxxxxxxxx>
> Signed-off-by: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
> ---
>   drivers/hwtracing/stm/Kconfig  | 14 +++++
>   drivers/hwtracing/stm/Makefile |  2 +
>   drivers/hwtracing/stm/p_ost.c  | 95 ++++++++++++++++++++++++++++++++++
>   3 files changed, 111 insertions(+)
>   create mode 100644 drivers/hwtracing/stm/p_ost.c
>
> diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
> index aad594fe79cc..0b52901125f7 100644
> --- a/drivers/hwtracing/stm/Kconfig
> +++ b/drivers/hwtracing/stm/Kconfig
> @@ -41,6 +41,20 @@ config STM_PROTO_SYS_T
>   
>   	  If you don't know what this is, say N.
>   
> +config STM_PROTO_OST
> +	tristate "MIPI OST STM framing protocol driver"
> +	default CONFIG_STM
> +	help
> +	  This is an implementation of MIPI OST protocol to be used
> +	  over the STP transport. In addition to the data payload, it
> +	  also carries additional metadata for entity, better
> +	  means of trace source identification, etc.
> +
> +	  The receiving side must be able to decode this protocol in
> +	  addition to the MIPI STP, in order to extract the data.
> +
> +	  If you don't know what this is, say N.
> +
>   config STM_DUMMY
>   	tristate "Dummy STM driver"
>   	help
> diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile
> index 1692fcd29277..715fc721891e 100644
> --- a/drivers/hwtracing/stm/Makefile
> +++ b/drivers/hwtracing/stm/Makefile
> @@ -5,9 +5,11 @@ stm_core-y		:= core.o policy.o
>   
>   obj-$(CONFIG_STM_PROTO_BASIC) += stm_p_basic.o
>   obj-$(CONFIG_STM_PROTO_SYS_T) += stm_p_sys-t.o
> +obj-$(CONFIG_STM_PROTO_OST) += stm_p_ost.o
>   
>   stm_p_basic-y		:= p_basic.o
>   stm_p_sys-t-y		:= p_sys-t.o
> +stm_p_ost-y		:= p_ost.o
>   
>   obj-$(CONFIG_STM_DUMMY)	+= dummy_stm.o
>   
> diff --git a/drivers/hwtracing/stm/p_ost.c b/drivers/hwtracing/stm/p_ost.c
> new file mode 100644
> index 000000000000..2ca1a3fda57f
> --- /dev/null
> +++ b/drivers/hwtracing/stm/p_ost.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copied from drivers/hwtracing/stm.p-sys-t.c as of commit d69d5e83110f
> + * ("stm class: Add MIPI SyS-T protocol support").
> + *
> + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
> + * Copyright (c) 2020 The Linux Foundation. All rights reserved.
> + * Copyright (c) 2018, Intel Corporation.
> + *
> + * MIPI OST framing protocol for STM devices.
> + */
> +
> +#include <linux/configfs.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/slab.h>
> +#include <linux/stm.h>
> +#include <linux/sched/clock.h>
> +#include "stm.h"
> +
> +#define OST_TOKEN_STARTSIMPLE		(0x10)
> +#define OST_VERSION_MIPI1		(0x10 << 8)
> +#define OST_ENTITY_FTRACE		(0x01 << 16)
> +#define OST_CONTROL_PROTOCOL		(0x0 << 24)
> +
> +#define DATA_HEADER (OST_TOKEN_STARTSIMPLE | OST_VERSION_MIPI1 | \
> +			OST_ENTITY_FTRACE | OST_CONTROL_PROTOCOL)
> +
> +#define STM_MAKE_VERSION(ma, mi)	((ma << 8) | mi)
> +#define STM_HEADER_MAGIC		(0x5953)
> +
> +static ssize_t notrace ost_write(struct stm_data *data,
> +		struct stm_output *output, unsigned int chan,
> +		const char *buf, size_t count)
> +{
> +	unsigned int c = output->channel + chan;
> +	unsigned int m = output->master;
> +	const unsigned char nil = 0;
> +	u32 header = DATA_HEADER;
> +	u8 trc_hdr[24];
> +	ssize_t sz;
> +
> +	/*
> +	 * STP framing rules for OST frames:
> +	 *   * the first packet of the OST frame is marked;
> +	 *   * the last packet is a FLAG.
> +	 */
> +	/* Message layout: HEADER / DATA / TAIL */
> +	/* HEADER */
> +
> +	sz = data->packet(data, m, c, STP_PACKET_DATA, STP_PACKET_MARKED,
> +			  4, (u8 *)&header);
> +	if (sz <= 0)
> +		return sz;
> +	*(uint16_t *)(trc_hdr) = STM_MAKE_VERSION(0, 3);
> +	*(uint16_t *)(trc_hdr + 2) = STM_HEADER_MAGIC;
> +	*(uint32_t *)(trc_hdr + 4) = raw_smp_processor_id();
> +	*(uint64_t *)(trc_hdr + 8) = sched_clock();
> +	*(uint64_t *)(trc_hdr + 16) = task_tgid_nr(get_current());
> +	sz = stm_data_write(data, m, c, false, trc_hdr, sizeof(trc_hdr));
> +	if (sz <= 0)
> +		return sz;
> +
> +	/* DATA */
> +	sz = stm_data_write(data, m, c, false, buf, count);
> +
> +	/* TAIL */
> +	if (sz > 0)
> +		data->packet(data, m, c, STP_PACKET_FLAG,
> +			STP_PACKET_TIMESTAMPED, 0, &nil);
> +
> +	return sz;
> +}
> +
> +static const struct stm_protocol_driver ost_pdrv = {
> +	.owner			= THIS_MODULE,
> +	.name			= "p_ost",
> +	.write			= ost_write,
> +};
> +
> +static int ost_stm_init(void)
> +{
> +	return stm_register_protocol(&ost_pdrv);
> +}
> +
> +static void ost_stm_exit(void)
> +{
> +	stm_unregister_protocol(&ost_pdrv);
> +}
> +
> +module_init(ost_stm_init);
> +module_exit(ost_stm_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("MIPI Open System Trace STM framing protocol driver");