[Cbe-oss-dev] Spider DMA wrongness
Linas Vepstas
linas at austin.ibm.com
Fri Dec 15 10:12:29 EST 2006
On Thu, Dec 14, 2006 at 02:21:12PM -0600, linas wrote:
> On Tue, Nov 07, 2006 at 04:43:07PM +1100, Benjamin Herrenschmidt wrote:
> >
> > - The descriptor ring mixes up descriptors themselves and driver
> > specific data. This is pretty bad. That means bad cache behaviour and
> > the descriptors as seen by the hardware aren't nicely next to each other
> > in memory, thus defeating any possible attempt at prefetching the chip
> > might be doing (most network chips do aggressive prefetching of
> > descriptors, I don't know for sure about spider). We should really
> > really really (I insist :-) split the actual descriptors manipulated by
> > the driver and the device (DMA) from the driver data structures. The
>
> Guhh. I just unearthed this old, unread chain of notes. I'll try
> sending a patch shortly.
Here it is.
Subject: [PATCH/RFC] Spidernet: separate hardware state from driver state.
This patch separates the hardware descriptor state from the
driver descriptor state, per suggestion from Ben Herrenschmidt.
This compiles and boots and seems to work. I can't evaluate
performance or stress test till Jim comes back. Thus, if anyone
is interested, they can play around with this, but I'm not sending
upstream at this time.
Signed-off-by: Linas Vepstas <linas at austin.ibm.com>
----
drivers/net/spider_net.c | 148 ++++++++++++++++++++++++++---------------------
drivers/net/spider_net.h | 16 +++--
2 files changed, 95 insertions(+), 69 deletions(-)
Index: linux-2.6.19-git7/drivers/net/spider_net.h
===================================================================
--- linux-2.6.19-git7.orig/drivers/net/spider_net.h 2006-12-14 14:04:58.000000000 -0600
+++ linux-2.6.19-git7/drivers/net/spider_net.h 2006-12-14 16:28:16.000000000 -0600
@@ -24,7 +24,7 @@
#ifndef _SPIDER_NET_H
#define _SPIDER_NET_H
-#define VERSION "1.6 B"
+#define VERSION "1.6 C"
#include "sungem_phy.h"
@@ -356,8 +356,8 @@ enum spider_net_int2_status {
#define SPIDER_NET_DESCR_NOT_IN_USE 0xF0000000
#define SPIDER_NET_DESCR_TXDESFLG 0x00800000
-struct spider_net_descr {
- /* as defined by the hardware */
+/* Descriptor, as defined by the hardware */
+struct spider_net_hw_descr {
u32 buf_addr;
u32 buf_size;
u32 next_descr_addr;
@@ -366,13 +366,15 @@ struct spider_net_descr {
u32 valid_size; /* all zeroes for tx */
u32 data_status;
u32 data_error; /* all zeroes for tx */
+} __attribute__((aligned(32)));
- /* used in the driver */
+struct spider_net_descr {
+ struct spider_net_hw_descr *hwdescr;
struct sk_buff *skb;
u32 bus_addr;
struct spider_net_descr *next;
struct spider_net_descr *prev;
-} __attribute__((aligned(32)));
+};
struct spider_net_descr_chain {
spinlock_t lock;
@@ -380,6 +382,7 @@ struct spider_net_descr_chain {
struct spider_net_descr *tail;
struct spider_net_descr *ring;
int num_desc;
+ struct spider_net_hw_descr *hwring;
dma_addr_t dma_addr;
};
@@ -452,6 +455,9 @@ struct spider_net_card {
struct net_device_stats netdev_stats;
struct spider_net_extra_stats spider_stats;
struct spider_net_options options;
+
+ /* Must be last item in struct */
+ struct spider_net_descr darray[0];
};
#define pr_err(fmt,arg...) \
Index: linux-2.6.19-git7/drivers/net/spider_net.c
===================================================================
--- linux-2.6.19-git7.orig/drivers/net/spider_net.c 2006-12-14 14:04:58.000000000 -0600
+++ linux-2.6.19-git7/drivers/net/spider_net.c 2006-12-14 16:21:03.000000000 -0600
@@ -263,9 +263,9 @@ spider_net_get_mac_address(struct net_de
* returns the status as in the dmac_cmd_status field of the descriptor
*/
static inline int
-spider_net_get_descr_status(struct spider_net_descr *descr)
+spider_net_get_descr_status(struct spider_net_hw_descr *hwdescr)
{
- return descr->dmac_cmd_status & SPIDER_NET_DESCR_IND_PROC_MASK;
+ return hwdescr->dmac_cmd_status & SPIDER_NET_DESCR_IND_PROC_MASK;
}
/**
@@ -283,12 +283,12 @@ spider_net_free_chain(struct spider_net_
descr = chain->ring;
do {
descr->bus_addr = 0;
- descr->next_descr_addr = 0;
+ descr->hwdescr->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);
+ chain->hwring, chain->dma_addr);
}
/**
@@ -307,29 +307,34 @@ spider_net_init_chain(struct spider_net_
{
int i;
struct spider_net_descr *descr;
+ struct spider_net_hw_descr *hwdescr;
dma_addr_t buf;
size_t alloc_size;
- alloc_size = chain->num_desc * sizeof (struct spider_net_descr);
+ alloc_size = chain->num_desc * sizeof(struct spider_net_hw_descr);
- chain->ring = dma_alloc_coherent(&card->pdev->dev, alloc_size,
+ chain->hwring = dma_alloc_coherent(&card->pdev->dev, alloc_size,
&chain->dma_addr, GFP_KERNEL);
- if (!chain->ring)
+ if (!chain->hwring)
return -ENOMEM;
+ memset(chain->ring, 0, chain->num_desc * sizeof(struct spider_net_descr));
+
/* Set up the hardware pointers in each descriptor */
descr = chain->ring;
+ hwdescr = chain->hwring;
buf = chain->dma_addr;
- for (i=0; i < chain->num_desc; i++, descr++) {
- descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+ for (i=0; i < chain->num_desc; i++, descr++, hwdescr++) {
+ hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+ hwdescr->next_descr_addr = 0;
+ descr->hwdescr = hwdescr;
descr->bus_addr = buf;
- descr->next_descr_addr = 0;
descr->next = descr + 1;
descr->prev = descr - 1;
- buf += sizeof(struct spider_net_descr);
+ buf += sizeof(struct spider_net_hw_descr);
}
/* do actual circular list */
(descr-1)->next = chain->ring;
@@ -356,7 +361,7 @@ spider_net_free_rx_chain_contents(struct
do {
if (descr->skb) {
dev_kfree_skb(descr->skb);
- pci_unmap_single(card->pdev, descr->buf_addr,
+ pci_unmap_single(card->pdev, descr->hwdescr->buf_addr,
SPIDER_NET_MAX_FRAME,
PCI_DMA_BIDIRECTIONAL);
}
@@ -378,6 +383,7 @@ static int
spider_net_prepare_rx_descr(struct spider_net_card *card,
struct spider_net_descr *descr)
{
+ struct spider_net_hw_descr *hwdescr = descr->hwdescr;
dma_addr_t buf;
int offset;
int bufsize;
@@ -396,11 +402,11 @@ spider_net_prepare_rx_descr(struct spide
card->spider_stats.alloc_rx_skb_error++;
return -ENOMEM;
}
- descr->buf_size = bufsize;
- descr->result_size = 0;
- descr->valid_size = 0;
- descr->data_status = 0;
- descr->data_error = 0;
+ hwdescr->buf_size = bufsize;
+ hwdescr->result_size = 0;
+ hwdescr->valid_size = 0;
+ hwdescr->data_status = 0;
+ hwdescr->data_error = 0;
offset = ((unsigned long)descr->skb->data) &
(SPIDER_NET_RXBUF_ALIGN - 1);
@@ -409,21 +415,21 @@ spider_net_prepare_rx_descr(struct spide
/* iommu-map the skb */
buf = pci_map_single(card->pdev, descr->skb->data,
SPIDER_NET_MAX_FRAME, PCI_DMA_FROMDEVICE);
- descr->buf_addr = buf;
if (pci_dma_mapping_error(buf)) {
dev_kfree_skb_any(descr->skb);
if (netif_msg_rx_err(card) && net_ratelimit())
pr_err("Could not iommu-map rx buffer\n");
card->spider_stats.rx_iommu_map_error++;
- descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+ hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
} else {
- descr->next_descr_addr = 0;
+ hwdescr->buf_addr = buf;
+ hwdescr->next_descr_addr = 0;
wmb();
- descr->dmac_cmd_status = SPIDER_NET_DESCR_CARDOWNED |
+ hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_CARDOWNED |
SPIDER_NET_DMAC_NOINTR_COMPLETE;
wmb();
- descr->prev->next_descr_addr = descr->bus_addr;
+ descr->prev->hwdescr->next_descr_addr = descr->bus_addr;
}
return 0;
@@ -479,7 +485,7 @@ spider_net_refill_rx_chain(struct spider
if (!spin_trylock_irqsave(&chain->lock, flags))
return;
- while (spider_net_get_descr_status(chain->head) ==
+ while (spider_net_get_descr_status(chain->head->hwdescr) ==
SPIDER_NET_DESCR_NOT_IN_USE) {
if (spider_net_prepare_rx_descr(card, chain->head))
break;
@@ -641,6 +647,7 @@ spider_net_prepare_tx_descr(struct spide
struct sk_buff *skb)
{
struct spider_net_descr *descr;
+ struct spider_net_hw_descr *hwdescr;
dma_addr_t buf;
unsigned long flags;
@@ -655,30 +662,32 @@ spider_net_prepare_tx_descr(struct spide
spin_lock_irqsave(&card->tx_chain.lock, flags);
descr = card->tx_chain.head;
+ hwdescr = descr->hwdescr;
card->tx_chain.head = descr->next;
- descr->buf_addr = buf;
- descr->buf_size = skb->len;
- descr->next_descr_addr = 0;
descr->skb = skb;
- descr->data_status = 0;
+ hwdescr->buf_addr = buf;
+ hwdescr->buf_size = skb->len;
+ hwdescr->next_descr_addr = 0;
+ hwdescr->data_status = 0;
- descr->dmac_cmd_status =
+ hwdescr->dmac_cmd_status =
SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
spin_unlock_irqrestore(&card->tx_chain.lock, flags);
if (skb->protocol == htons(ETH_P_IP))
switch (skb->nh.iph->protocol) {
case IPPROTO_TCP:
- descr->dmac_cmd_status |= SPIDER_NET_DMAC_TCP;
+ hwdescr->dmac_cmd_status |= SPIDER_NET_DMAC_TCP;
break;
case IPPROTO_UDP:
- descr->dmac_cmd_status |= SPIDER_NET_DMAC_UDP;
+ hwdescr->dmac_cmd_status |= SPIDER_NET_DMAC_UDP;
break;
}
/* Chain the bus address, so that the DMA engine finds this descr. */
- descr->prev->next_descr_addr = descr->bus_addr;
+ wmb();
+ descr->prev->hwdescr->next_descr_addr = descr->bus_addr;
card->netdev->trans_start = jiffies; /* set netdev watchdog timer */
return 0;
@@ -687,16 +696,17 @@ spider_net_prepare_tx_descr(struct spide
static int
spider_net_set_low_watermark(struct spider_net_card *card)
{
+ struct spider_net_descr *descr = card->tx_chain.tail;
+ struct spider_net_hw_descr *hwdescr;
unsigned long flags;
int status;
int cnt=0;
int i;
- struct spider_net_descr *descr = card->tx_chain.tail;
/* Measure the length of the queue. Measurement does not
* need to be precise -- does not need a lock. */
while (descr != card->tx_chain.head) {
- status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
+ status = descr->hwdescr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
if (status == SPIDER_NET_DESCR_NOT_IN_USE)
break;
descr = descr->next;
@@ -715,10 +725,12 @@ spider_net_set_low_watermark(struct spid
/* Set the new watermark, clear the old watermark */
spin_lock_irqsave(&card->tx_chain.lock, flags);
- descr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
- if (card->low_watermark && card->low_watermark != descr)
- card->low_watermark->dmac_cmd_status =
- card->low_watermark->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
+ descr->hwdescr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
+ if (card->low_watermark && card->low_watermark != descr) {
+ hwdescr = card->low_watermark->hwdescr;
+ hwdescr->dmac_cmd_status =
+ hwdescr->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
+ }
card->low_watermark = descr;
spin_unlock_irqrestore(&card->tx_chain.lock, flags);
return cnt;
@@ -741,6 +753,7 @@ spider_net_release_tx_chain(struct spide
{
struct spider_net_descr_chain *chain = &card->tx_chain;
struct spider_net_descr *descr;
+ struct spider_net_hw_descr *hwdescr;
struct sk_buff *skb;
u32 buf_addr;
unsigned long flags;
@@ -749,8 +762,9 @@ spider_net_release_tx_chain(struct spide
while (chain->tail != chain->head) {
spin_lock_irqsave(&chain->lock, flags);
descr = chain->tail;
+ hwdescr = descr->hwdescr;
- status = spider_net_get_descr_status(descr);
+ status = spider_net_get_descr_status(hwdescr);
switch (status) {
case SPIDER_NET_DESCR_COMPLETE:
card->netdev_stats.tx_packets++;
@@ -786,9 +800,9 @@ spider_net_release_tx_chain(struct spide
}
chain->tail = descr->next;
- descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
+ hwdescr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
skb = descr->skb;
- buf_addr = descr->buf_addr;
+ buf_addr = hwdescr->buf_addr;
spin_unlock_irqrestore(&chain->lock, flags);
/* unmap the skb */
@@ -824,7 +838,7 @@ spider_net_kick_tx_dma(struct spider_net
descr = card->tx_chain.tail;
for (;;) {
- if (spider_net_get_descr_status(descr) ==
+ if (spider_net_get_descr_status(descr->hwdescr) ==
SPIDER_NET_DESCR_CARDOWNED) {
spider_net_write_reg(card, SPIDER_NET_GDTDCHA,
descr->bus_addr);
@@ -920,17 +934,18 @@ static void
spider_net_pass_skb_up(struct spider_net_descr *descr,
struct spider_net_card *card)
{
+ struct spider_net_hw_descr *hwdescr= descr->hwdescr;
struct sk_buff *skb;
struct net_device *netdev;
u32 data_status, data_error;
- data_status = descr->data_status;
- data_error = descr->data_error;
+ data_status = hwdescr->data_status;
+ data_error = hwdescr->data_error;
netdev = card->netdev;
skb = descr->skb;
skb->dev = netdev;
- skb_put(skb, descr->valid_size);
+ skb_put(skb, hwdescr->valid_size);
/* the card seems to add 2 bytes of junk in front
* of the ethernet frame */
@@ -1006,9 +1021,10 @@ spider_net_decode_one_descr(struct spide
{
struct spider_net_descr_chain *chain = &card->rx_chain;
struct spider_net_descr *descr = chain->tail;
+ struct spider_net_hw_descr *hwdescr = descr->hwdescr;
int status;
- status = spider_net_get_descr_status(descr);
+ status = spider_net_get_descr_status(hwdescr);
/* Nothing in the descriptor, or ring must be empty */
if ((status == SPIDER_NET_DESCR_CARDOWNED) ||
@@ -1019,7 +1035,7 @@ spider_net_decode_one_descr(struct spide
chain->tail = descr->next;
/* unmap descriptor */
- pci_unmap_single(card->pdev, descr->buf_addr,
+ pci_unmap_single(card->pdev, hwdescr->buf_addr,
SPIDER_NET_MAX_FRAME, PCI_DMA_FROMDEVICE);
if ( (status == SPIDER_NET_DESCR_RESPONSE_ERROR) ||
@@ -1042,27 +1058,26 @@ spider_net_decode_one_descr(struct spide
}
/* The cases we'll throw away the packet immediately */
- if (descr->data_error & SPIDER_NET_DESTROY_RX_FLAGS) {
+ if (hwdescr->data_error & SPIDER_NET_DESTROY_RX_FLAGS) {
if (netif_msg_rx_err(card))
pr_err("%s: error in received descriptor found, "
"data_status=x%08x, data_error=x%08x\n",
card->netdev->name,
- descr->data_status, descr->data_error);
+ hwdescr->data_status, hwdescr->data_error);
goto bad_desc;
}
- if (descr->dmac_cmd_status & 0xfefe) {
+ if (hwdescr->dmac_cmd_status & 0xfefe) {
pr_err("%s: bad status, cmd_status=x%08x\n",
card->netdev->name,
- descr->dmac_cmd_status);
- pr_err("buf_addr=x%08x\n", descr->buf_addr);
- pr_err("buf_size=x%08x\n", descr->buf_size);
- pr_err("next_descr_addr=x%08x\n", descr->next_descr_addr);
- pr_err("result_size=x%08x\n", descr->result_size);
- pr_err("valid_size=x%08x\n", descr->valid_size);
- pr_err("data_status=x%08x\n", descr->data_status);
- pr_err("data_error=x%08x\n", descr->data_error);
- pr_err("bus_addr=x%08x\n", descr->bus_addr);
+ hwdescr->dmac_cmd_status);
+ pr_err("buf_addr=x%08x\n", hwdescr->buf_addr);
+ pr_err("buf_size=x%08x\n", hwdescr->buf_size);
+ pr_err("next_descr_addr=x%08x\n", hwdescr->next_descr_addr);
+ pr_err("result_size=x%08x\n", hwdescr->result_size);
+ pr_err("valid_size=x%08x\n", hwdescr->valid_size);
+ pr_err("data_status=x%08x\n", hwdescr->data_status);
+ pr_err("data_error=x%08x\n", hwdescr->data_error);
pr_err("which=%ld\n", descr - card->rx_chain.ring);
card->spider_stats.rx_desc_error++;
@@ -1071,12 +1086,12 @@ spider_net_decode_one_descr(struct spide
/* Ok, we've got a packet in descr */
spider_net_pass_skb_up(descr, card);
- descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+ hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
return 1;
bad_desc:
dev_kfree_skb_irq(descr->skb);
- descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+ hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
return 0;
}
@@ -2043,9 +2058,6 @@ spider_net_setup_netdev(struct spider_ne
card->options.rx_csum = SPIDER_NET_RX_CSUM_DEFAULT;
- card->tx_chain.num_desc = tx_descriptors;
- card->rx_chain.num_desc = rx_descriptors;
-
spider_net_setup_netdev_ops(netdev);
netdev->features = NETIF_F_HW_CSUM | NETIF_F_LLTX;
@@ -2093,8 +2105,11 @@ spider_net_alloc_card(void)
{
struct net_device *netdev;
struct spider_net_card *card;
+ size_t alloc_size;
- netdev = alloc_etherdev(sizeof(struct spider_net_card));
+ alloc_size = sizeof(struct spider_net_card) +
+ (tx_descriptors + rx_descriptors) * sizeof(struct spider_net_descr);
+ netdev = alloc_etherdev(alloc_size);
if (!netdev)
return NULL;
@@ -2105,6 +2120,11 @@ spider_net_alloc_card(void)
init_waitqueue_head(&card->waitq);
atomic_set(&card->tx_timeout_task_counter, 0);
+ card->rx_chain.num_desc = rx_descriptors;
+ card->rx_chain.ring = card->darray;
+ card->tx_chain.num_desc = tx_descriptors;
+ card->tx_chain.ring = card->darray + rx_descriptors;
+
return card;
}
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