// 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) 2021-2022 Qualcomm Innovation Center, Inc. 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 __nocfi 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 v2");
MODULE_DESCRIPTION("MIPI Open System Trace STM framing protocol driver");