[RFC] NTB: Use DMA Engine to transmit and receive

From: Jon Mason
Date: Mon Jul 01 2013 - 14:36:27 EST

Allocate and use a DMA engine channel to transmit and receive data over
NTB. If none is allocated, fall back to using the CPU to transfer data.

Signed-off-by: Jon Mason <jon.mason@xxxxxxxxx>
---
drivers/ntb/ntb_hw.c | 19 ++-
drivers/ntb/ntb_hw.h | 1 +
drivers/ntb/ntb_transport.c | 285 ++++++++++++++++++++++++++++++++++++-------
3 files changed, 259 insertions(+), 46 deletions(-)

diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
index 15d7517..d032f6d 100644
--- a/drivers/ntb/ntb_hw.c
+++ b/drivers/ntb/ntb_hw.c
@@ -56,7 +56,7 @@
#include "ntb_regs.h"

#define NTB_NAME "Intel(R) PCI-E Non-Transparent Bridge Driver"
-#define NTB_VER "0.25"
+#define NTB_VER "0.26"

MODULE_DESCRIPTION(NTB_NAME);
MODULE_VERSION(NTB_VER);
@@ -396,6 +396,23 @@ int ntb_read_remote_spad(struct ntb_device *ndev, unsigned int idx, u32 *val)
}

/**
+ * ntb_get_mw_base() - get addr for the NTB memory window
+ * @ndev: pointer to ntb_device instance
+ * @mw: memory window number
+ *
+ * This function provides the base address of the memory window specified.
+ *
+ * RETURNS: address, or NULL on error.
+ */
+resource_size_t ntb_get_mw_base(struct ntb_device *ndev, unsigned int mw)
+{
+ if (mw >= NTB_NUM_MW)
+ return 0;
+
+ return pci_resource_start(ndev->pdev, MW_TO_BAR(mw));
+}
+
+/**
* ntb_get_mw_vbase() - get virtual addr for the NTB memory window
* @ndev: pointer to ntb_device instance
* @mw: memory window number
diff --git a/drivers/ntb/ntb_hw.h b/drivers/ntb/ntb_hw.h
index f2b11ef..b631070 100644
--- a/drivers/ntb/ntb_hw.h
+++ b/drivers/ntb/ntb_hw.h
@@ -206,6 +206,7 @@ int ntb_write_local_spad(struct ntb_device *ndev, unsigned int idx, u32 val);
int ntb_read_local_spad(struct ntb_device *ndev, unsigned int idx, u32 *val);
int ntb_write_remote_spad(struct ntb_device *ndev, unsigned int idx, u32 val);
int ntb_read_remote_spad(struct ntb_device *ndev, unsigned int idx, u32 *val);
+resource_size_t ntb_get_mw_base(struct ntb_device *ndev, unsigned int mw);
void __iomem *ntb_get_mw_vbase(struct ntb_device *ndev, unsigned int mw);
u64 ntb_get_mw_size(struct ntb_device *ndev, unsigned int mw);
void ntb_ring_sdb(struct ntb_device *ndev, unsigned int idx);
diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index 9694ed8..e86134b 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -47,6 +47,7 @@
*/
#include <linux/debugfs.h>
#include <linux/delay.h>
+#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/errno.h>
#include <linux/export.h>
@@ -68,6 +69,10 @@ static unsigned char max_num_clients = 2;
module_param(max_num_clients, byte, 0644);
MODULE_PARM_DESC(max_num_clients, "Maximum number of NTB transport clients");

+static unsigned int copy_bytes = 1024;
+module_param(copy_bytes, uint, 0644);
+MODULE_PARM_DESC(copy_bytes, "Threshold under which NTB will use the CPU to copy instead of DMA");
+
struct ntb_queue_entry {
/* ntb_queue list reference */
struct list_head entry;
@@ -76,6 +81,13 @@ struct ntb_queue_entry {
void *buf;
unsigned int len;
unsigned int flags;
+
+ struct ntb_transport_qp *qp;
+ union {
+ struct ntb_payload_header __iomem *tx_hdr;
+ struct ntb_payload_header *rx_hdr;
+ };
+ unsigned int index;
};

struct ntb_rx_info {
@@ -86,6 +98,7 @@ struct ntb_transport_qp {
struct ntb_transport *transport;
struct ntb_device *ndev;
void *cb_data;
+ struct dma_chan *dma_chan;

bool client_ready;
bool qp_link;
@@ -99,6 +112,7 @@ struct ntb_transport_qp {
struct list_head tx_free_q;
spinlock_t ntb_tx_free_q_lock;
void __iomem *tx_mw;
+ dma_addr_t tx_mw_raw;
unsigned int tx_index;
unsigned int tx_max_entry;
unsigned int tx_max_frame;
@@ -113,6 +127,7 @@ struct ntb_transport_qp {
unsigned int rx_index;
unsigned int rx_max_entry;
unsigned int rx_max_frame;
+ dma_cookie_t last_cookie;

void (*event_handler) (void *data, int status);
struct delayed_work link_work;
@@ -128,9 +143,14 @@ struct ntb_transport_qp {
u64 rx_err_no_buf;
u64 rx_err_oflow;
u64 rx_err_ver;
+ u64 rx_memcpy;
+ u64 rx_async;
u64 tx_bytes;
u64 tx_pkts;
u64 tx_ring_full;
+ u64 tx_err_no_buf;
+ u64 tx_memcpy;
+ u64 tx_async;
};

struct ntb_transport_mw {
@@ -381,7 +401,7 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
char *buf;
ssize_t ret, out_offset, out_count;

- out_count = 600;
+ out_count = 1000;

buf = kmalloc(out_count, GFP_KERNEL);
if (!buf)
@@ -396,6 +416,10 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"rx_pkts - \t%llu\n", qp->rx_pkts);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "rx_memcpy - \t%llu\n", qp->rx_memcpy);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "rx_async - \t%llu\n", qp->rx_async);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
"rx_ring_empty - %llu\n", qp->rx_ring_empty);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"rx_err_no_buf - %llu\n", qp->rx_err_no_buf);
@@ -415,8 +439,14 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"tx_pkts - \t%llu\n", qp->tx_pkts);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "tx_memcpy - \t%llu\n", qp->tx_memcpy);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "tx_async - \t%llu\n", qp->tx_async);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
"tx_ring_full - \t%llu\n", qp->tx_ring_full);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "tx_err_no_buf - %llu\n", qp->tx_err_no_buf);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
"tx_mw - \t%p\n", qp->tx_mw);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"tx_index - \t%u\n", qp->tx_index);
@@ -485,11 +515,11 @@ static void ntb_transport_setup_qp_mw(struct ntb_transport *nt,
num_qps_mw = nt->max_qps / NTB_NUM_MW;

rx_size = (unsigned int) nt->mw[mw_num].size / num_qps_mw;
- qp->remote_rx_info = nt->mw[mw_num].virt_addr +
- (qp_num / NTB_NUM_MW * rx_size);
+ qp->rx_buff = nt->mw[mw_num].virt_addr + qp_num / NTB_NUM_MW * rx_size;
rx_size -= sizeof(struct ntb_rx_info);

- qp->rx_buff = qp->remote_rx_info + 1;
+ qp->remote_rx_info = qp->rx_buff + rx_size;
+
/* Due to housekeeping, there must be atleast 2 buffs */
qp->rx_max_frame = min(transport_mtu, rx_size / 2);
qp->rx_max_entry = rx_size / qp->rx_max_frame;
@@ -799,6 +829,7 @@ static void ntb_transport_init_queue(struct ntb_transport *nt,
struct ntb_transport_qp *qp;
unsigned int num_qps_mw, tx_size;
u8 mw_num = QP_TO_MW(qp_num);
+ u64 qp_offset;

qp = &nt->qps[qp_num];
qp->qp_num = qp_num;
@@ -814,11 +845,12 @@ static void ntb_transport_init_queue(struct ntb_transport *nt,
num_qps_mw = nt->max_qps / NTB_NUM_MW;

tx_size = (unsigned int) ntb_get_mw_size(qp->ndev, mw_num) / num_qps_mw;
- qp->rx_info = ntb_get_mw_vbase(nt->ndev, mw_num) +
- (qp_num / NTB_NUM_MW * tx_size);
+ qp_offset = qp_num / NTB_NUM_MW * tx_size;
+ qp->tx_mw = ntb_get_mw_vbase(nt->ndev, mw_num) + qp_offset;
+ qp->tx_mw_raw = ntb_get_mw_base(qp->ndev, mw_num) + qp_offset;
tx_size -= sizeof(struct ntb_rx_info);
+ qp->rx_info = qp->tx_mw + tx_size;

- qp->tx_mw = qp->rx_info + 1;
/* Due to housekeeping, there must be atleast 2 buffs */
qp->tx_max_frame = min(transport_mtu, tx_size / 2);
qp->tx_max_entry = tx_size / qp->tx_max_frame;
@@ -942,13 +974,22 @@ void ntb_transport_free(void *transport)
kfree(nt);
}

-static void ntb_rx_copy_task(struct ntb_transport_qp *qp,
- struct ntb_queue_entry *entry, void *offset)
+static void ntb_rx_copy_callback(void *data)
{
+ struct ntb_queue_entry *entry = data;
+ struct ntb_transport_qp *qp = entry->qp;
void *cb_data = entry->cb_data;
unsigned int len = entry->len;
+ struct ntb_payload_header *hdr = entry->rx_hdr;
+
+ wmb();
+ hdr->flags = 0;

- memcpy(entry->buf, offset, entry->len);
+ /* If the callbacks come out of order, the writing of the index to the
+ * last completed will be out of order. This may result in the the
+ * receive stalling forever.
+ */
+ iowrite32(entry->index, &qp->rx_info->entry);

ntb_list_add(&qp->ntb_rx_free_q_lock, &entry->entry, &qp->rx_free_q);

@@ -956,6 +997,80 @@ static void ntb_rx_copy_task(struct ntb_transport_qp *qp,
qp->rx_handler(qp, qp->cb_data, cb_data, len);
}

+static void ntb_memcpy_rx(struct ntb_queue_entry *entry, void *offset)
+{
+ void *buf = entry->buf;
+ size_t len = entry->len;
+
+ memcpy(buf, offset, len);
+
+ ntb_rx_copy_callback(entry);
+}
+
+static void ntb_async_rx(struct ntb_queue_entry *entry, void *offset,
+ size_t len)
+{
+ struct dma_async_tx_descriptor *txd;
+ struct ntb_transport_qp *qp = entry->qp;
+ struct dma_chan *chan = qp->dma_chan;
+ struct dma_device *device;
+ dma_addr_t src, dest;
+ dma_cookie_t cookie;
+ void *buf = entry->buf;
+ unsigned long flags;
+
+ entry->len = len;
+
+ if (!chan)
+ goto err;
+
+ device = chan->device;
+
+ if (len < copy_bytes ||
+ !is_dma_copy_aligned(device, __pa(offset), __pa(buf), len))
+ goto err1;
+
+ dest = dma_map_single(device->dev, buf, len, DMA_FROM_DEVICE);
+ if (dma_mapping_error(device->dev, dest))
+ goto err1;
+
+ src = dma_map_single(device->dev, offset, len, DMA_TO_DEVICE);
+ if (dma_mapping_error(device->dev, src))
+ goto err2;
+
+ flags = DMA_COMPL_DEST_UNMAP_SINGLE | DMA_COMPL_SRC_UNMAP_SINGLE |
+ DMA_PREP_INTERRUPT;
+ txd = device->device_prep_dma_memcpy(chan, dest, src, len, flags);
+ if (!txd)
+ goto err3;
+
+ txd_clear_parent(txd);
+ txd_clear_next(txd);
+ txd->callback = ntb_rx_copy_callback;
+ txd->callback_param = entry;
+
+ cookie = dmaengine_submit(txd);
+ if (dma_submit_error(cookie))
+ goto err3;
+
+ qp->last_cookie = cookie;
+
+ dma_async_issue_pending(chan);
+ qp->rx_async++;
+
+ return;
+
+err3:
+ dma_unmap_single(device->dev, src, len, DMA_TO_DEVICE);
+err2:
+ dma_unmap_single(device->dev, dest, len, DMA_FROM_DEVICE);
+err1:
+ dma_sync_wait(chan, qp->last_cookie);
+err:
+ ntb_memcpy_rx(entry, offset);
+ qp->rx_memcpy++;
+}
+
static int ntb_process_rxc(struct ntb_transport_qp *qp)
{
struct ntb_payload_header *hdr;
@@ -994,41 +1109,44 @@ static int ntb_process_rxc(struct ntb_transport_qp *qp)
if (hdr->flags & LINK_DOWN_FLAG) {
ntb_qp_link_down(qp);

- ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
- &qp->rx_pend_q);
- goto out;
+ goto err;
}

dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
"rx offset %u, ver %u - %d payload received, buf size %d\n",
qp->rx_index, hdr->ver, hdr->len, entry->len);

- if (hdr->len <= entry->len) {
- entry->len = hdr->len;
- ntb_rx_copy_task(qp, entry, offset);
- } else {
- ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
- &qp->rx_pend_q);
+ qp->rx_bytes += hdr->len;
+ qp->rx_pkts++;

+ if (hdr->len > entry->len) {
qp->rx_err_oflow++;
dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
"RX overflow! Wanted %d got %d\n",
hdr->len, entry->len);
+
+ goto err;
}

- qp->rx_bytes += hdr->len;
- qp->rx_pkts++;
+ entry->index = qp->rx_index;
+ entry->rx_hdr = hdr;

-out:
- /* Ensure that the data is fully copied out before clearing the flag */
- wmb();
- hdr->flags = 0;
- iowrite32(qp->rx_index, &qp->rx_info->entry);
+ ntb_async_rx(entry, offset, hdr->len);

+out:
qp->rx_index++;
qp->rx_index %= qp->rx_max_entry;

return 0;
+
+err:
+ ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
+ &qp->rx_pend_q);
+ wmb();
+ hdr->flags = 0;
+ iowrite32(qp->rx_index, &qp->rx_info->entry);
+
+ goto out;
}

static int ntb_transport_rxc_db(void *data, int db_num)
@@ -1051,19 +1169,12 @@ static int ntb_transport_rxc_db(void *data, int db_num)
return i;
}

-static void ntb_tx_copy_task(struct ntb_transport_qp *qp,
- struct ntb_queue_entry *entry,
- void __iomem *offset)
+static void ntb_tx_copy_callback(void *data)
{
- struct ntb_payload_header __iomem *hdr;
-
- memcpy_toio(offset, entry->buf, entry->len);
-
- hdr = offset + qp->tx_max_frame - sizeof(struct ntb_payload_header);
- iowrite32(entry->len, &hdr->len);
- iowrite32((u32) qp->tx_pkts, &hdr->ver);
+ struct ntb_queue_entry *entry = data;
+ struct ntb_transport_qp *qp = entry->qp;
+ struct ntb_payload_header __iomem *hdr = entry->tx_hdr;

- /* Ensure that the data is fully copied out before setting the flag */
wmb();
iowrite32(entry->flags | DESC_DONE_FLAG, &hdr->flags);

@@ -1084,15 +1195,79 @@ static void ntb_tx_copy_task(struct ntb_transport_qp *qp,
ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry, &qp->tx_free_q);
}

-static int ntb_process_tx(struct ntb_transport_qp *qp,
- struct ntb_queue_entry *entry)
+static void ntb_memcpy_tx(struct ntb_queue_entry *entry, void __iomem *offset)
+{
+ memcpy_toio(offset, entry->buf, entry->len);
+
+ ntb_tx_copy_callback(entry);
+}
+
+static void ntb_async_tx(struct ntb_transport_qp *qp,
+ struct ntb_queue_entry *entry)
{
+ struct dma_async_tx_descriptor *txd;
+ struct dma_chan *chan = qp->dma_chan;
+ struct dma_device *device;
+ dma_addr_t src, dest;
+ dma_cookie_t cookie;
+ struct ntb_payload_header __iomem *hdr;
void __iomem *offset;
+ size_t len = entry->len;
+ void *buf = entry->buf;
+ unsigned long flags;

offset = qp->tx_mw + qp->tx_max_frame * qp->tx_index;
+ hdr = offset + qp->tx_max_frame - sizeof(struct ntb_payload_header);
+ entry->tx_hdr = hdr;
+
+ iowrite32(entry->len, &hdr->len);
+ iowrite32((u32) qp->tx_pkts, &hdr->ver);
+
+ if (!chan)
+ goto err;

- dev_dbg(&ntb_query_pdev(qp->ndev)->dev, "%lld - offset %p, tx %u, entry len %d flags %x buff %p\n",
- qp->tx_pkts, offset, qp->tx_index, entry->len, entry->flags,
+ device = chan->device;
+
+ dest = qp->tx_mw_raw + qp->tx_max_frame * qp->tx_index;
+
+ if (len < copy_bytes ||
+ !is_dma_copy_aligned(device, __pa(buf), dest, len))
+ goto err;
+
+ src = dma_map_single(device->dev, buf, len, DMA_TO_DEVICE);
+ if (dma_mapping_error(device->dev, src))
+ goto err;
+
+ flags = DMA_COMPL_SRC_UNMAP_SINGLE | DMA_PREP_INTERRUPT;
+ txd = device->device_prep_dma_memcpy(chan, dest, src, len, flags);
+ if (!txd)
+ goto err1;
+
+ txd_clear_parent(txd);
+ txd_clear_next(txd);
+ txd->callback = ntb_tx_copy_callback;
+ txd->callback_param = entry;
+
+ cookie = dmaengine_submit(txd);
+ if (dma_submit_error(cookie))
+ goto err1;
+
+ dma_async_issue_pending(chan);
+ qp->tx_async++;
+
+ return;
+err1:
+ dma_unmap_single(device->dev, src, len, DMA_TO_DEVICE);
+err:
+ ntb_memcpy_tx(entry, offset);
+ qp->tx_memcpy++;
+}
+
+static int ntb_process_tx(struct ntb_transport_qp *qp,
+ struct ntb_queue_entry *entry)
+{
+ dev_dbg(&ntb_query_pdev(qp->ndev)->dev, "%lld - tx %u, entry len %d flags %x buff %p\n",
+ qp->tx_pkts, qp->tx_index, entry->len, entry->flags,
entry->buf);
if (qp->tx_index == qp->remote_rx_info->entry) {
qp->tx_ring_full++;
@@ -1108,7 +1283,7 @@ static int ntb_process_tx(struct ntb_transport_qp *qp,
return 0;
}

- ntb_tx_copy_task(qp, entry, offset);
+ ntb_async_tx(qp, entry);

qp->tx_index++;
qp->tx_index %= qp->tx_max_entry;
@@ -1194,11 +1369,16 @@ ntb_transport_create_queue(void *data, struct pci_dev *pdev,
qp->tx_handler = handlers->tx_handler;
qp->event_handler = handlers->event_handler;

+ qp->dma_chan = dma_find_channel(DMA_MEMCPY);
+ if (!qp->dma_chan)
+ dev_info(&pdev->dev, "Unable to allocate private DMA channel, using CPU instead\n");
+
for (i = 0; i < NTB_QP_DEF_NUM_ENTRIES; i++) {
entry = kzalloc(sizeof(struct ntb_queue_entry), GFP_ATOMIC);
if (!entry)
goto err1;

+ entry->qp = qp;
ntb_list_add(&qp->ntb_rx_free_q_lock, &entry->entry,
&qp->rx_free_q);
}
@@ -1208,6 +1388,7 @@ ntb_transport_create_queue(void *data, struct pci_dev *pdev,
if (!entry)
goto err2;

+ entry->qp = qp;
ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry,
&qp->tx_free_q);
}
@@ -1249,10 +1430,13 @@ void ntb_transport_free_queue(struct ntb_transport_qp *qp)

pdev = ntb_query_pdev(qp->ndev);

- cancel_delayed_work_sync(&qp->link_work);
+ if (qp->dma_chan)
+ dmaengine_terminate_all(qp->dma_chan);

ntb_unregister_db_callback(qp->ndev, qp->qp_num);

+ cancel_delayed_work_sync(&qp->link_work);
+
while ((entry = ntb_list_rm(&qp->ntb_rx_free_q_lock, &qp->rx_free_q)))
kfree(entry);

@@ -1358,8 +1542,10 @@ int ntb_transport_tx_enqueue(struct ntb_transport_qp *qp, void *cb, void *data,
return -EINVAL;

entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q);
- if (!entry)
+ if (!entry) {
+ qp->tx_err_no_buf++;
return -ENOMEM;
+ }

entry->cb_data = cb;
entry->buf = data;
@@ -1475,9 +1661,18 @@ EXPORT_SYMBOL_GPL(ntb_transport_qp_num);
*/
unsigned int ntb_transport_max_size(struct ntb_transport_qp *qp)
{
+ unsigned int max;
+
if (!qp)
return 0;

- return qp->tx_max_frame - sizeof(struct ntb_payload_header);
+ if (!qp->dma_chan)
+ return qp->tx_max_frame - sizeof(struct ntb_payload_header);
+
+ /* If DMA engine usage is possible, try to find the max size for that */
+ max = qp->tx_max_frame - sizeof(struct ntb_payload_header);
+ max -= max % (1 << qp->dma_chan->device->copy_align);
+
+ return max;
}
EXPORT_SYMBOL_GPL(ntb_transport_max_size);
--
1.7.9.5

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