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Spidernet DMA coalescing
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The current driver code performs 512 DMA mappings of a bunch of
32-byte ring descriptor structures. This is silly, as they are
all in contiguous memory. This patch changes the code to
dma_map_coherent() each rx/tx ring as a whole.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
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Linas Vepstas authored and Jeff Garzik committed Feb 5, 2007
1 parent 8343246 commit d4ed8f8
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Showing 3 changed files with 54 additions and 70 deletions.
103 changes: 47 additions & 56 deletions drivers/net/spider_net.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -280,72 +280,67 @@ spider_net_free_chain(struct spider_net_card *card,
{
struct spider_net_descr *descr;

for (descr = chain->tail; !descr->bus_addr; descr = descr->next) {
pci_unmap_single(card->pdev, descr->bus_addr,
SPIDER_NET_DESCR_SIZE, PCI_DMA_BIDIRECTIONAL);
descr = chain->ring;
do {
descr->bus_addr = 0;
}
descr->next_descr_addr = 0;
descr = descr->next;
} while (descr != chain->ring);

dma_free_coherent(&card->pdev->dev, chain->num_desc,
chain->ring, chain->dma_addr);
}

/**
* spider_net_init_chain - links descriptor chain
* spider_net_init_chain - alloc and link descriptor chain
* @card: card structure
* @chain: address of chain
* @start_descr: address of descriptor array
* @no: number of descriptors
*
* we manage a circular list that mirrors the hardware structure,
* We manage a circular list that mirrors the hardware structure,
* except that the hardware uses bus addresses.
*
* returns 0 on success, <0 on failure
* Returns 0 on success, <0 on failure
*/
static int
spider_net_init_chain(struct spider_net_card *card,
struct spider_net_descr_chain *chain,
struct spider_net_descr *start_descr,
int no)
struct spider_net_descr_chain *chain)
{
int i;
struct spider_net_descr *descr;
dma_addr_t buf;
size_t alloc_size;

descr = start_descr;
memset(descr, 0, sizeof(*descr) * no);
alloc_size = chain->num_desc * sizeof (struct spider_net_descr);

/* set up the hardware pointers in each descriptor */
for (i=0; i<no; i++, descr++) {
descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
chain->ring = dma_alloc_coherent(&card->pdev->dev, alloc_size,
&chain->dma_addr, GFP_KERNEL);

buf = pci_map_single(card->pdev, descr,
SPIDER_NET_DESCR_SIZE,
PCI_DMA_BIDIRECTIONAL);
if (!chain->ring)
return -ENOMEM;

if (pci_dma_mapping_error(buf))
goto iommu_error;
descr = chain->ring;
memset(descr, 0, alloc_size);

/* Set up the hardware pointers in each descriptor */
buf = chain->dma_addr;
for (i=0; i < chain->num_desc; i++, descr++) {
descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;

descr->bus_addr = buf;
descr->next_descr_addr = 0;
descr->next = descr + 1;
descr->prev = descr - 1;

buf += sizeof(struct spider_net_descr);
}
/* do actual circular list */
(descr-1)->next = start_descr;
start_descr->prev = descr-1;
(descr-1)->next = chain->ring;
chain->ring->prev = descr-1;

spin_lock_init(&chain->lock);
chain->head = start_descr;
chain->tail = start_descr;

chain->head = chain->ring;
chain->tail = chain->ring;
return 0;

iommu_error:
descr = start_descr;
for (i=0; i < no; i++, descr++)
if (descr->bus_addr)
pci_unmap_single(card->pdev, descr->bus_addr,
SPIDER_NET_DESCR_SIZE,
PCI_DMA_BIDIRECTIONAL);
return -ENOMEM;
}

/**
Expand Down Expand Up @@ -707,7 +702,7 @@ spider_net_set_low_watermark(struct spider_net_card *card)
}

/* If TX queue is short, don't even bother with interrupts */
if (cnt < card->num_tx_desc/4)
if (cnt < card->tx_chain.num_desc/4)
return cnt;

/* Set low-watermark 3/4th's of the way into the queue. */
Expand Down Expand Up @@ -1652,26 +1647,25 @@ spider_net_open(struct net_device *netdev)
{
struct spider_net_card *card = netdev_priv(netdev);
struct spider_net_descr *descr;
int i, result;
int result;

result = -ENOMEM;
if (spider_net_init_chain(card, &card->tx_chain, card->descr,
card->num_tx_desc))
result = spider_net_init_chain(card, &card->tx_chain);
if (result)
goto alloc_tx_failed;

card->low_watermark = NULL;

/* rx_chain is after tx_chain, so offset is descr + tx_count */
if (spider_net_init_chain(card, &card->rx_chain,
card->descr + card->num_tx_desc,
card->num_rx_desc))
result = spider_net_init_chain(card, &card->rx_chain);
if (result)
goto alloc_rx_failed;

descr = card->rx_chain.head;
for (i=0; i < card->num_rx_desc; i++, descr++)
/* Make a ring of of bus addresses */
descr = card->rx_chain.ring;
do {
descr->next_descr_addr = descr->next->bus_addr;
descr = descr->next;
} while (descr != card->rx_chain.ring);

/* allocate rx skbs */
/* Allocate rx skbs */
if (spider_net_alloc_rx_skbs(card))
goto alloc_skbs_failed;

Expand Down Expand Up @@ -1924,6 +1918,7 @@ spider_net_stop(struct net_device *netdev)

/* release chains */
spider_net_release_tx_chain(card, 1);
spider_net_free_rx_chain_contents(card);

spider_net_free_rx_chain_contents(card);

Expand Down Expand Up @@ -2057,8 +2052,8 @@ spider_net_setup_netdev(struct spider_net_card *card)

card->options.rx_csum = SPIDER_NET_RX_CSUM_DEFAULT;

card->num_tx_desc = tx_descriptors;
card->num_rx_desc = rx_descriptors;
card->tx_chain.num_desc = tx_descriptors;
card->rx_chain.num_desc = rx_descriptors;

spider_net_setup_netdev_ops(netdev);

Expand Down Expand Up @@ -2107,12 +2102,8 @@ spider_net_alloc_card(void)
{
struct net_device *netdev;
struct spider_net_card *card;
size_t alloc_size;

alloc_size = sizeof (*card) +
sizeof (struct spider_net_descr) * rx_descriptors +
sizeof (struct spider_net_descr) * tx_descriptors;
netdev = alloc_etherdev(alloc_size);
netdev = alloc_etherdev(sizeof(struct spider_net_card));
if (!netdev)
return NULL;

Expand Down
17 changes: 5 additions & 12 deletions drivers/net/spider_net.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -378,6 +378,9 @@ struct spider_net_descr_chain {
spinlock_t lock;
struct spider_net_descr *head;
struct spider_net_descr *tail;
struct spider_net_descr *ring;
int num_desc;
dma_addr_t dma_addr;
};

/* descriptor data_status bits */
Expand All @@ -397,8 +400,6 @@ struct spider_net_descr_chain {
* 701b8000 would be correct, but every packets gets that flag */
#define SPIDER_NET_DESTROY_RX_FLAGS 0x700b8000

#define SPIDER_NET_DESCR_SIZE 32

/* this will be bigger some time */
struct spider_net_options {
int rx_csum; /* for rx: if 0 ip_summed=NONE,
Expand Down Expand Up @@ -441,25 +442,17 @@ struct spider_net_card {
struct spider_net_descr_chain rx_chain;
struct spider_net_descr *low_watermark;

struct net_device_stats netdev_stats;

struct spider_net_options options;

spinlock_t intmask_lock;
struct tasklet_struct rxram_full_tl;
struct timer_list tx_timer;

struct work_struct tx_timeout_task;
atomic_t tx_timeout_task_counter;
wait_queue_head_t waitq;

/* for ethtool */
int msg_enable;
int num_rx_desc;
int num_tx_desc;
struct net_device_stats netdev_stats;
struct spider_net_extra_stats spider_stats;

struct spider_net_descr descr[0];
struct spider_net_options options;
};

#define pr_err(fmt,arg...) \
Expand Down
4 changes: 2 additions & 2 deletions drivers/net/spider_net_ethtool.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -158,9 +158,9 @@ spider_net_ethtool_get_ringparam(struct net_device *netdev,
struct spider_net_card *card = netdev->priv;

ering->tx_max_pending = SPIDER_NET_TX_DESCRIPTORS_MAX;
ering->tx_pending = card->num_tx_desc;
ering->tx_pending = card->tx_chain.num_desc;
ering->rx_max_pending = SPIDER_NET_RX_DESCRIPTORS_MAX;
ering->rx_pending = card->num_rx_desc;
ering->rx_pending = card->rx_chain.num_desc;
}

static int spider_net_get_stats_count(struct net_device *netdev)
Expand Down

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