/******************************************************************************
 *
 * Copyright(c) 2003 - 2008 Intel Corporation. All rights reserved.
 *
 * Portions of this file are derived from the ipw3945 project, as well
 * as portions of the ieee80211 subsystem header files.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License 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.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
 *
 * The full GNU General Public License is included in this distribution in the
 * file called LICENSE.
 *
 * Contact Information:
 * James P. Ketrenos <ipw2100-admin@linux.intel.com>
 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 *
 *****************************************************************************/

#include <net/mac80211.h>
#include "iwl-eeprom.h"
#include "iwl-dev.h"
#include "iwl-core.h"
#include "iwl-sta.h"
#include "iwl-io.h"
#include "iwl-helpers.h"
/************************** RX-FUNCTIONS ****************************/
/*
 * Rx theory of operation
 *
 * Driver allocates a circular buffer of Receive Buffer Descriptors (RBDs),
 * each of which point to Receive Buffers to be filled by the NIC.  These get
 * used not only for Rx frames, but for any command response or notification
 * from the NIC.  The driver and NIC manage the Rx buffers by means
 * of indexes into the circular buffer.
 *
 * Rx Queue Indexes
 * The host/firmware share two index registers for managing the Rx buffers.
 *
 * The READ index maps to the first position that the firmware may be writing
 * to -- the driver can read up to (but not including) this position and get
 * good data.
 * The READ index is managed by the firmware once the card is enabled.
 *
 * The WRITE index maps to the last position the driver has read from -- the
 * position preceding WRITE is the last slot the firmware can place a packet.
 *
 * The queue is empty (no good data) if WRITE = READ - 1, and is full if
 * WRITE = READ.
 *
 * During initialization, the host sets up the READ queue position to the first
 * INDEX position, and WRITE to the last (READ - 1 wrapped)
 *
 * When the firmware places a packet in a buffer, it will advance the READ index
 * and fire the RX interrupt.  The driver can then query the READ index and
 * process as many packets as possible, moving the WRITE index forward as it
 * resets the Rx queue buffers with new memory.
 *
 * The management in the driver is as follows:
 * + A list of pre-allocated SKBs is stored in iwl->rxq->rx_free.  When
 *   iwl->rxq->free_count drops to or below RX_LOW_WATERMARK, work is scheduled
 *   to replenish the iwl->rxq->rx_free.
 * + In iwl_rx_replenish (scheduled) if 'processed' != 'read' then the
 *   iwl->rxq is replenished and the READ INDEX is updated (updating the
 *   'processed' and 'read' driver indexes as well)
 * + A received packet is processed and handed to the kernel network stack,
 *   detached from the iwl->rxq.  The driver 'processed' index is updated.
 * + The Host/Firmware iwl->rxq is replenished at tasklet time from the rx_free
 *   list. If there are no allocated buffers in iwl->rxq->rx_free, the READ
 *   INDEX is not incremented and iwl->status(RX_STALLED) is set.  If there
 *   were enough free buffers and RX_STALLED is set it is cleared.
 *
 *
 * Driver sequence:
 *
 * iwl_rx_queue_alloc()   Allocates rx_free
 * iwl_rx_replenish()     Replenishes rx_free list from rx_used, and calls
 *                            iwl_rx_queue_restock
 * iwl_rx_queue_restock() Moves available buffers from rx_free into Rx
 *                            queue, updates firmware pointers, and updates
 *                            the WRITE index.  If insufficient rx_free buffers
 *                            are available, schedules iwl_rx_replenish
 *
 * -- enable interrupts --
 * ISR - iwl_rx()         Detach iwl_rx_mem_buffers from pool up to the
 *                            READ INDEX, detaching the SKB from the pool.
 *                            Moves the packet buffer from queue to rx_used.
 *                            Calls iwl_rx_queue_restock to refill any empty
 *                            slots.
 * ...
 *
 */

/**
 * iwl_rx_queue_space - Return number of free slots available in queue.
 */
int iwl_rx_queue_space(const struct iwl_rx_queue *q)
{
	int s = q->read - q->write;
	if (s <= 0)
		s += RX_QUEUE_SIZE;
	/* keep some buffer to not confuse full and empty queue */
	s -= 2;
	if (s < 0)
		s = 0;
	return s;
}
EXPORT_SYMBOL(iwl_rx_queue_space);

/**
 * iwl_rx_queue_update_write_ptr - Update the write pointer for the RX queue
 */
int iwl_rx_queue_update_write_ptr(struct iwl_priv *priv, struct iwl_rx_queue *q)
{
	u32 reg = 0;
	int ret = 0;
	unsigned long flags;

	spin_lock_irqsave(&q->lock, flags);

	if (q->need_update == 0)
		goto exit_unlock;

	/* If power-saving is in use, make sure device is awake */
	if (test_bit(STATUS_POWER_PMI, &priv->status)) {
		reg = iwl_read32(priv, CSR_UCODE_DRV_GP1);

		if (reg & CSR_UCODE_DRV_GP1_BIT_MAC_SLEEP) {
			iwl_set_bit(priv, CSR_GP_CNTRL,
				    CSR_GP_CNTRL_REG_FLAG_MAC_ACCESS_REQ);
			goto exit_unlock;
		}

		ret = iwl_grab_nic_access(priv);
		if (ret)
			goto exit_unlock;

		/* Device expects a multiple of 8 */
		iwl_write_direct32(priv, FH_RSCSR_CHNL0_WPTR,
				     q->write & ~0x7);
		iwl_release_nic_access(priv);

	/* Else device is assumed to be awake */
	} else
		/* Device expects a multiple of 8 */
		iwl_write32(priv, FH_RSCSR_CHNL0_WPTR, q->write & ~0x7);


	q->need_update = 0;

 exit_unlock:
	spin_unlock_irqrestore(&q->lock, flags);
	return ret;
}
EXPORT_SYMBOL(iwl_rx_queue_update_write_ptr);
/**
 * iwl_dma_addr2rbd_ptr - convert a DMA address to a uCode read buffer ptr
 */
static inline __le32 iwl_dma_addr2rbd_ptr(struct iwl_priv *priv,
					  dma_addr_t dma_addr)
{
	return cpu_to_le32((u32)(dma_addr >> 8));
}

/**
 * iwl_rx_queue_restock - refill RX queue from pre-allocated pool
 *
 * If there are slots in the RX queue that need to be restocked,
 * and we have free pre-allocated buffers, fill the ranks as much
 * as we can, pulling from rx_free.
 *
 * This moves the 'write' index forward to catch up with 'processed', and
 * also updates the memory address in the firmware to reference the new
 * target buffer.
 */
int iwl_rx_queue_restock(struct iwl_priv *priv)
{
	struct iwl_rx_queue *rxq = &priv->rxq;
	struct list_head *element;
	struct iwl_rx_mem_buffer *rxb;
	unsigned long flags;
	int write;
	int ret = 0;

	spin_lock_irqsave(&rxq->lock, flags);
	write = rxq->write & ~0x7;
	while ((iwl_rx_queue_space(rxq) > 0) && (rxq->free_count)) {
		/* Get next free Rx buffer, remove from free list */
		element = rxq->rx_free.next;
		rxb = list_entry(element, struct iwl_rx_mem_buffer, list);
		list_del(element);

		/* Point to Rx buffer via next RBD in circular buffer */
		rxq->bd[rxq->write] = iwl_dma_addr2rbd_ptr(priv, rxb->dma_addr);
		rxq->queue[rxq->write] = rxb;
		rxq->write = (rxq->write + 1) & RX_QUEUE_MASK;
		rxq->free_count--;
	}
	spin_unlock_irqrestore(&rxq->lock, flags);
	/* If the pre-allocated buffer pool is dropping low, schedule to
	 * refill it */
	if (rxq->free_count <= RX_LOW_WATERMARK)
		queue_work(priv->workqueue, &priv->rx_replenish);


	/* If we've added more space for the firmware to place data, tell it.
	 * Increment device's write pointer in multiples of 8. */
	if ((write != (rxq->write & ~0x7))
	    || (abs(rxq->write - rxq->read) > 7)) {
		spin_lock_irqsave(&rxq->lock, flags);
		rxq->need_update = 1;
		spin_unlock_irqrestore(&rxq->lock, flags);
		ret = iwl_rx_queue_update_write_ptr(priv, rxq);
	}

	return ret;
}
EXPORT_SYMBOL(iwl_rx_queue_restock);


/**
 * iwl_rx_replenish - Move all used packet from rx_used to rx_free
 *
 * When moving to rx_free an SKB is allocated for the slot.
 *
 * Also restock the Rx queue via iwl_rx_queue_restock.
 * This is called as a scheduled work item (except for during initialization)
 */
void iwl_rx_allocate(struct iwl_priv *priv)
{
	struct iwl_rx_queue *rxq = &priv->rxq;
	struct list_head *element;
	struct iwl_rx_mem_buffer *rxb;
	unsigned long flags;
	spin_lock_irqsave(&rxq->lock, flags);
	while (!list_empty(&rxq->rx_used)) {
		element = rxq->rx_used.next;
		rxb = list_entry(element, struct iwl_rx_mem_buffer, list);

		/* Alloc a new receive buffer */
		rxb->skb = alloc_skb(priv->hw_params.rx_buf_size,
				__GFP_NOWARN | GFP_ATOMIC);
		if (!rxb->skb) {
			if (net_ratelimit())
				printk(KERN_CRIT DRV_NAME
				       ": Can not allocate SKB buffers\n");
			/* We don't reschedule replenish work here -- we will
			 * call the restock method and if it still needs
			 * more buffers it will schedule replenish */
			break;
		}
		priv->alloc_rxb_skb++;
		list_del(element);

		/* Get physical address of RB/SKB */
		rxb->dma_addr =
		    pci_map_single(priv->pci_dev, rxb->skb->data,
			   priv->hw_params.rx_buf_size, PCI_DMA_FROMDEVICE);
		list_add_tail(&rxb->list, &rxq->rx_free);
		rxq->free_count++;
	}
	spin_unlock_irqrestore(&rxq->lock, flags);
}
EXPORT_SYMBOL(iwl_rx_allocate);

void iwl_rx_replenish(struct iwl_priv *priv)
{
	unsigned long flags;

	iwl_rx_allocate(priv);

	spin_lock_irqsave(&priv->lock, flags);
	iwl_rx_queue_restock(priv);
	spin_unlock_irqrestore(&priv->lock, flags);
}
EXPORT_SYMBOL(iwl_rx_replenish);


/* Assumes that the skb field of the buffers in 'pool' is kept accurate.
 * If an SKB has been detached, the POOL needs to have its SKB set to NULL
 * This free routine walks the list of POOL entries and if SKB is set to
 * non NULL it is unmapped and freed
 */
void iwl_rx_queue_free(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
{
	int i;
	for (i = 0; i < RX_QUEUE_SIZE + RX_FREE_BUFFERS; i++) {
		if (rxq->pool[i].skb != NULL) {
			pci_unmap_single(priv->pci_dev,
					 rxq->pool[i].dma_addr,
					 priv->hw_params.rx_buf_size,
					 PCI_DMA_FROMDEVICE);
			dev_kfree_skb(rxq->pool[i].skb);
		}
	}

	pci_free_consistent(priv->pci_dev, 4 * RX_QUEUE_SIZE, rxq->bd,
			    rxq->dma_addr);
	rxq->bd = NULL;
}
EXPORT_SYMBOL(iwl_rx_queue_free);

int iwl_rx_queue_alloc(struct iwl_priv *priv)
{
	struct iwl_rx_queue *rxq = &priv->rxq;
	struct pci_dev *dev = priv->pci_dev;
	int i;

	spin_lock_init(&rxq->lock);
	INIT_LIST_HEAD(&rxq->rx_free);
	INIT_LIST_HEAD(&rxq->rx_used);

	/* Alloc the circular buffer of Read Buffer Descriptors (RBDs) */
	rxq->bd = pci_alloc_consistent(dev, 4 * RX_QUEUE_SIZE, &rxq->dma_addr);
	if (!rxq->bd)
		return -ENOMEM;

	/* Fill the rx_used queue with _all_ of the Rx buffers */
	for (i = 0; i < RX_FREE_BUFFERS + RX_QUEUE_SIZE; i++)
		list_add_tail(&rxq->pool[i].list, &rxq->rx_used);

	/* Set us so that we have processed and used all buffers, but have
	 * not restocked the Rx queue with fresh buffers */
	rxq->read = rxq->write = 0;
	rxq->free_count = 0;
	rxq->need_update = 0;
	return 0;
}
EXPORT_SYMBOL(iwl_rx_queue_alloc);

void iwl_rx_queue_reset(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
{
	unsigned long flags;
	int i;
	spin_lock_irqsave(&rxq->lock, flags);
	INIT_LIST_HEAD(&rxq->rx_free);
	INIT_LIST_HEAD(&rxq->rx_used);
	/* Fill the rx_used queue with _all_ of the Rx buffers */
	for (i = 0; i < RX_FREE_BUFFERS + RX_QUEUE_SIZE; i++) {
		/* In the reset function, these buffers may have been allocated
		 * to an SKB, so we need to unmap and free potential storage */
		if (rxq->pool[i].skb != NULL) {
			pci_unmap_single(priv->pci_dev,
					 rxq->pool[i].dma_addr,
					 priv->hw_params.rx_buf_size,
					 PCI_DMA_FROMDEVICE);
			priv->alloc_rxb_skb--;
			dev_kfree_skb(rxq->pool[i].skb);
			rxq->pool[i].skb = NULL;
		}
		list_add_tail(&rxq->pool[i].list, &rxq->rx_used);
	}

	/* Set us so that we have processed and used all buffers, but have
	 * not restocked the Rx queue with fresh buffers */
	rxq->read = rxq->write = 0;
	rxq->free_count = 0;
	spin_unlock_irqrestore(&rxq->lock, flags);
}
EXPORT_SYMBOL(iwl_rx_queue_reset);

