/******************************************************************************
*
* Copyright(c) 2003 - 2013 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:
* Intel Linux Wireless <ilw@linux.intel.com>
* Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
*
*****************************************************************************/
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/gfp.h>
#include "iwl-prph.h"
#include "iwl-io.h"
#include "internal.h"
#include "iwl-op-mode.h"
/******************************************************************************
*
* RX path 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_pcie_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 irq thread 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_rxq_alloc() Allocates rx_free
* iwl_pcie_rx_replenish() Replenishes rx_free list from rx_used, and calls
* iwl_pcie_rxq_restock
* iwl_pcie_rxq_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_pcie_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_pcie_rxq_restock to refill any empty
* slots.
* ...
*
*/
/*
* iwl_rxq_space - Return number of free slots available in queue.
*/
static int iwl_rxq_space(const struct iwl_rxq *rxq)
{
int s = rxq->read - rxq->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;
}
/*
* iwl_dma_addr2rbd_ptr - convert a DMA address to a uCode read buffer ptr
*/
static inline __le32 iwl_pcie_dma_addr2rbd_ptr(dma_addr_t dma_addr)
{
return cpu_to_le32((u32)(dma_addr >> 8));
}
/*
* iwl_pcie_rx_stop - stops the Rx DMA
*/
int iwl_pcie_rx_stop(struct iwl_tran