b43: Add PIO support for PCMCIA devices

This adds PIO support back (D'oh!) for PCMCIA devices.
This is a complete rewrite of the old PIO code. It does actually work
and we get reasonable performance out of it on a modern machine.
On a PowerBook G4 I get a few MBit for TX and a few more for RX.
So it doesn't work as well as DMA (of course), but it's a _lot_ faster
than the old PIO code (only got a few kBit with that).

The limiting factor is the host CPU speed. So it will generate 100%
CPU usage when the network interface is heavily loaded. A voluntary preemption
point in the RX path makes sure Desktop Latency isn't hurt.

PIO is needed for 16bit PCMCIA devices, as we really don't want to poke with
the braindead DMA mechanisms on PCMCIA sockets. Additionally, not all
PCMCIA sockets do actually support DMA in 16bit mode (mine doesn't).

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 31 insertions, 6 deletions

diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index a4e6a59ccac8..355f28a2f7f5 100644
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -47,6 +47,7 @@
 #include "debugfs.h"
 #include "phy.h"
 #include "dma.h"
+#include "pio.h"
 #include "sysfs.h"
 #include "xmit.h"
 #include "lo.h"
@@ -1593,8 +1594,12 @@ static void b43_interrupt_tasklet(struct b43_wldev *dev)
                 handle_irq_noise(dev);
 
         /* Check the DMA reason registers for received data. */
-        if (dma_reason[0] & B43_DMAIRQ_RX_DONE)
-                b43_dma_rx(dev->dma.rx_ring);
+        if (dma_reason[0] & B43_DMAIRQ_RX_DONE) {
+                if (b43_using_pio_transfers(dev))
+                        b43_pio_rx(dev->pio.rx_queue);
+                else
+                        b43_dma_rx(dev->dma.rx_ring);
+        }
         B43_WARN_ON(dma_reason[1] & B43_DMAIRQ_RX_DONE);
         B43_WARN_ON(dma_reason[2] & B43_DMAIRQ_RX_DONE);
         B43_WARN_ON(dma_reason[3] & B43_DMAIRQ_RX_DONE);
@@ -2698,12 +2703,21 @@ static int b43_op_tx(struct ieee80211_hw *hw,
         struct b43_wldev *dev = wl->current_dev;
         int err = -ENODEV;
 
+        if (unlikely(skb->len < 2 + 2 + 6)) {
+                /* Too short, this can't be a valid frame. */
+                return -EINVAL;
+        }
+        B43_WARN_ON(skb_shinfo(skb)->nr_frags);
+
         if (unlikely(!dev))
                 goto out;
         if (unlikely(b43_status(dev) < B43_STAT_STARTED))
                 goto out;
-        /* DMA-TX is done without a global lock. */
-        err = b43_dma_tx(dev, skb, ctl);
+        /* TX is done without a global lock. */
+        if (b43_using_pio_transfers(dev))
+                err = b43_pio_tx(dev, skb, ctl);
+        else
+                err = b43_dma_tx(dev, skb, ctl);
 out:
         if (unlikely(err))
                 return NETDEV_TX_BUSY;
@@ -2897,7 +2911,10 @@ static int b43_op_get_tx_stats(struct ieee80211_hw *hw,
                 goto out;
         spin_lock_irqsave(&wl->irq_lock, flags);
         if (likely(b43_status(dev) >= B43_STAT_STARTED)) {
-                b43_dma_get_tx_stats(dev, stats);
+                if (b43_using_pio_transfers(dev))
+                        b43_pio_get_tx_stats(dev, stats);
+                else
+                        b43_dma_get_tx_stats(dev, stats);
                 err = 0;
         }
         spin_unlock_irqrestore(&wl->irq_lock, flags);
@@ -3366,6 +3383,7 @@ static void b43_wireless_core_stop(struct b43_wldev *dev)
 
         b43_set_status(dev, B43_STAT_INITIALIZED);
 
+        b43_pio_stop(dev);
         mutex_unlock(&wl->mutex);
         /* Must unlock as it would otherwise deadlock. No races here.
          * Cancel the possibly running self-rearming periodic work. */
@@ -3683,6 +3701,7 @@ static void b43_wireless_core_exit(struct b43_wldev *dev)
                 b43_rng_exit(dev->wl, false);
         }
         b43_dma_free(dev);
+        b43_pio_free(dev);
         b43_chip_exit(dev);
         b43_radio_turn_off(dev, 1);
         b43_switch_analog(dev, 0);
@@ -3780,7 +3799,13 @@ static int b43_wireless_core_init(struct b43_wldev *dev)
         /* Maximum Contention Window */
         b43_shm_write16(dev, B43_SHM_SCRATCH, B43_SHM_SC_MAXCONT, 0x3FF);
 
-        err = b43_dma_init(dev);
+        if ((dev->dev->bus->bustype == SSB_BUSTYPE_PCMCIA) || B43_FORCE_PIO) {
+                dev->__using_pio_transfers = 1;
+                err = b43_pio_init(dev);
+        } else {
+                dev->__using_pio_transfers = 0;
+                err = b43_dma_init(dev);
+        }
         if (err)
                 goto err_chip_exit;
         b43_qos_init(dev);