path: root/drivers/misc/genwqe/card_ddcb.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * IBM Accelerator Family 'GenWQE'
 *
 * (C) Copyright IBM Corp. 2013
 *
 * Author: Frank Haverkamp <haver@linux.vnet.ibm.com>
 * Author: Joerg-Stephan Vogt <jsvogt@de.ibm.com>
 * Author: Michael Jung <mijung@gmx.net>
 * Author: Michael Ruettger <michael@ibmra.de>
 */

/*
 * Device Driver Control Block (DDCB) queue support. Definition of
 * interrupt handlers for queue support as well as triggering the
 * health monitor code in case of problems. The current hardware uses
 * an MSI interrupt which is shared between error handling and
 * functional code.
 */

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/pci.h>
#include <linux/string.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/crc-itu-t.h>

#include "card_base.h"
#include "card_ddcb.h"

/*
 * N: next DDCB, this is where the next DDCB will be put.
 * A: active DDCB, this is where the code will look for the next completion.
 * x: DDCB is enqueued, we are waiting for its completion.

 * Situation (1): Empty queue
 *  +---+---+---+---+---+---+---+---+
 *  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 *  |   |   |   |   |   |   |   |   |
 *  +---+---+---+---+---+---+---+---+
 *           A/N
 *  enqueued_ddcbs = A - N = 2 - 2 = 0
 *
 * Situation (2): Wrapped, N > A
 *  +---+---+---+---+---+---+---+---+
 *  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 *  |   |   | x | x |   |   |   |   |
 *  +---+---+---+---+---+---+---+---+
 *            A       N
 *  enqueued_ddcbs = N - A = 4 - 2 = 2
 *
 * Situation (3): Queue wrapped, A > N
 *  +---+---+---+---+---+---+---+---+
 *  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 *  | x | x |   |   | x | x | x | x |
 *  +---+---+---+---+---+---+---+---+
 *            N       A
 *  enqueued_ddcbs = queue_max  - (A - N) = 8 - (4 - 2) = 6
 *
 * Situation (4a): Queue full N > A
 *  +---+---+---+---+---+---+---+---+
 *  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 *  | x | x | x | x | x | x | x |   |
 *  +---+---+---+---+---+---+---+---+
 *    A                           N
 *
 *  enqueued_ddcbs = N - A = 7 - 0 = 7
 *
 * Situation (4a): Queue full A > N
 *  +---+---+---+---+---+---+---+---+
 *  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 *  | x | x | x |   | x | x | x | x |
 *  +---+---+---+---+---+---+---+---+
 *                N   A
 *  enqueued_ddcbs = queue_max - (A - N) = 8 - (4 - 3) = 7
 */

static int queue_empty(struct ddcb_queue *queue)
{
	return queue->ddcb_next == queue->ddcb_act;
}

static int queue_enqueued_ddcbs(struct ddcb_queue *queue)
{
	if (queue->ddcb_next >= queue->ddcb_act)
		return queue->ddcb_next - queue->ddcb_act;

	return queue->ddcb_max - (queue->ddcb_act - queue->ddcb_next);
}

static int queue_free_ddcbs(struct ddcb_queue *queue)
{
	int free_ddcbs = queue->ddcb_max - queue_enqueued_ddcbs(queue)