mmc: host: Add one missing file to support ring buffer logging

/*

 * Copyright (c) 2017, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and

 * only version 2 as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#include <linux/mmc/ring_buffer.h>

#include <linux/mmc/host.h>

void mmc_stop_tracing(struct mmc_host *mmc)

{

	mmc->trace_buf.stop_tracing = true;

}

void mmc_trace_write(struct mmc_host *mmc,

			const char *fmt, ...)

{

	unsigned int idx;

	va_list args;

	char *event;

	unsigned long flags;

	char str[MMC_TRACE_EVENT_SZ];

	if (unlikely(!mmc->trace_buf.data) ||

			unlikely(mmc->trace_buf.stop_tracing))

		return;

	/*

	 * Here an increment and modulus is used to keep

	 * index within array bounds. The cast to unsigned is

	 * necessary so increment and rolover wraps to 0 correctly

	 */

	spin_lock_irqsave(&mmc->trace_buf.trace_lock, flags);

	mmc->trace_buf.wr_idx += 1;

	idx = ((unsigned int)mmc->trace_buf.wr_idx) &

			(MMC_TRACE_RBUF_NUM_EVENTS - 1);

	spin_unlock_irqrestore(&mmc->trace_buf.trace_lock, flags);

	/* Catch some unlikely machine specific wrap-around bug */

	if (unlikely(idx > (MMC_TRACE_RBUF_NUM_EVENTS - 1))) {

		pr_err("%s: %s: Invalid idx:%d for mmc trace, tracing stopped !\n",

			mmc_hostname(mmc), __func__, idx);

		mmc_stop_tracing(mmc);

		return;

	}

	event = &mmc->trace_buf.data[idx * MMC_TRACE_EVENT_SZ];

	va_start(args, fmt);

	snprintf(str, MMC_TRACE_EVENT_SZ, "<%d> %lld: %s: %s",

		raw_smp_processor_id(),

		ktime_to_ns(ktime_get()),

		mmc_hostname(mmc), fmt);

	memset(event, '\0', MMC_TRACE_EVENT_SZ);

	vscnprintf(event, MMC_TRACE_EVENT_SZ, str, args);

	va_end(args);

}

void mmc_trace_init(struct mmc_host *mmc)

{

	BUILD_BUG_ON_NOT_POWER_OF_2(MMC_TRACE_RBUF_NUM_EVENTS);

	mmc->trace_buf.data = (char *)

				__get_free_pages(GFP_KERNEL|__GFP_ZERO,

				MMC_TRACE_RBUF_SZ_ORDER);

	if (!mmc->trace_buf.data) {

		pr_err("%s: %s: Unable to allocate trace for mmc\n",

			__func__, mmc_hostname(mmc));

		return;

	}

	spin_lock_init(&mmc->trace_buf.trace_lock);

	mmc->trace_buf.wr_idx = -1;

}

void mmc_trace_free(struct mmc_host *mmc)

{

	if (mmc->trace_buf.data)

		free_pages((unsigned long)mmc->trace_buf.data,

			MMC_TRACE_RBUF_SZ_ORDER);

}

void mmc_dump_trace_buffer(struct mmc_host *mmc, struct seq_file *s)

{

	unsigned int idx, cur_idx;

	unsigned int N = MMC_TRACE_RBUF_NUM_EVENTS - 1;

	char *event;

	unsigned long flags;

	if (!mmc->trace_buf.data)

		return;

	spin_lock_irqsave(&mmc->trace_buf.trace_lock, flags);

	idx = ((unsigned int)mmc->trace_buf.wr_idx) & N;

	cur_idx = (idx + 1) & N;

	do {

		event = &mmc->trace_buf.data[cur_idx * MMC_TRACE_EVENT_SZ];

		if (s)

			seq_printf(s, "%s", (char *)event);

		else

			pr_err("%s", (char *)event);

		cur_idx = (cur_idx + 1) & N;

		if (cur_idx == idx) {

			event =

			  &mmc->trace_buf.data[cur_idx * MMC_TRACE_EVENT_SZ];

			if (s)

				seq_printf(s, "latest_event: %s",

					(char *)event);

			else

				pr_err("latest_event: %s", (char *)event);

			break;

		}

	} while (1);

	spin_unlock_irqrestore(&mmc->trace_buf.trace_lock, flags);

}