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net: cdc_ncm: refactoring for tx multiplexing
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Adding multiplexed NDP support to cdc_ncm_fill_tx_frame, allowing
transmissions of multiple independent sessions within the same NTB.

Refactoring the code quite a bit to avoid having to store copies
of multiple NDPs being prepared for tx. The old code would still
reserve enough room for a maximum sized NDP in the skb so we might
as well keep them in the skb while they are being prepared.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Bjørn Mork authored and David S. Miller committed Oct 23, 2012
1 parent ff06ab1 commit c78b7c5
Showing 1 changed file with 102 additions and 145 deletions.
247 changes: 102 additions & 145 deletions drivers/net/usb/cdc_ncm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -88,14 +88,11 @@
(sizeof(struct usb_cdc_ncm_nth16) + sizeof(struct usb_cdc_ncm_ndp16) + \
(CDC_NCM_DPT_DATAGRAMS_MAX + 1) * sizeof(struct usb_cdc_ncm_dpe16))

struct cdc_ncm_data {
struct usb_cdc_ncm_nth16 nth16;
struct usb_cdc_ncm_ndp16 ndp16;
struct usb_cdc_ncm_dpe16 dpe16[CDC_NCM_DPT_DATAGRAMS_MAX + 1];
};
#define CDC_NCM_NDP_SIZE \
(sizeof(struct usb_cdc_ncm_ndp16) + \
(CDC_NCM_DPT_DATAGRAMS_MAX + 1) * sizeof(struct usb_cdc_ncm_dpe16))

struct cdc_ncm_ctx {
struct cdc_ncm_data tx_ncm;
struct usb_cdc_ncm_ntb_parameters ncm_parm;
struct hrtimer tx_timer;
struct tasklet_struct bh;
Expand All @@ -117,13 +114,12 @@ struct cdc_ncm_ctx {

struct sk_buff *tx_curr_skb;
struct sk_buff *tx_rem_skb;
__le32 tx_rem_sign;

spinlock_t mtx;
atomic_t stop;

u32 tx_timer_pending;
u32 tx_curr_offset;
u32 tx_curr_last_offset;
u32 tx_curr_frame_num;
u32 rx_speed;
u32 tx_speed;
Expand Down Expand Up @@ -658,51 +654,75 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
return ret;
}

static void cdc_ncm_zero_fill(u8 *ptr, u32 first, u32 end, u32 max)
static void cdc_ncm_align_tail(struct sk_buff *skb, size_t modulus, size_t remainder, size_t max)
{
if (first >= max)
return;
if (first >= end)
return;
if (end > max)
end = max;
memset(ptr + first, 0, end - first);
size_t align = ALIGN(skb->len, modulus) - skb->len + remainder;

if (skb->len + align > max)
align = max - skb->len;
if (align && skb_tailroom(skb) >= align)
memset(skb_put(skb, align), 0, align);
}

/* return a pointer to a valid struct usb_cdc_ncm_ndp16 of type sign, possibly
* allocating a new one within skb
*/
static struct usb_cdc_ncm_ndp16 *cdc_ncm_ndp(struct cdc_ncm_ctx *ctx, struct sk_buff *skb, __le32 sign, size_t reserve)
{
struct usb_cdc_ncm_ndp16 *ndp16 = NULL;
struct usb_cdc_ncm_nth16 *nth16 = (void *)skb->data;
size_t ndpoffset = le16_to_cpu(nth16->wNdpIndex);

/* follow the chain of NDPs, looking for a match */
while (ndpoffset) {
ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb->data + ndpoffset);
if (ndp16->dwSignature == sign)
return ndp16;
ndpoffset = le16_to_cpu(ndp16->wNextNdpIndex);
}

/* align new NDP */
cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_max);

/* verify that there is room for the NDP and the datagram (reserve) */
if ((ctx->tx_max - skb->len - reserve) < CDC_NCM_NDP_SIZE)
return NULL;

/* link to it */
if (ndp16)
ndp16->wNextNdpIndex = cpu_to_le16(skb->len);
else
nth16->wNdpIndex = cpu_to_le16(skb->len);

/* push a new empty NDP */
ndp16 = (struct usb_cdc_ncm_ndp16 *)memset(skb_put(skb, CDC_NCM_NDP_SIZE), 0, CDC_NCM_NDP_SIZE);
ndp16->dwSignature = sign;
ndp16->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp16) + sizeof(struct usb_cdc_ncm_dpe16));
return ndp16;
}

static struct sk_buff *
cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb, __le32 sign)
{
struct usb_cdc_ncm_nth16 *nth16;
struct usb_cdc_ncm_ndp16 *ndp16;
struct sk_buff *skb_out;
u32 rem;
u32 offset;
u32 last_offset;
u16 n = 0, index;
u16 n = 0, index, ndplen;
u8 ready2send = 0;

/* if there is a remaining skb, it gets priority */
if (skb != NULL)
if (skb != NULL) {
swap(skb, ctx->tx_rem_skb);
else
swap(sign, ctx->tx_rem_sign);
} else {
ready2send = 1;

/*
* +----------------+
* | skb_out |
* +----------------+
* ^ offset
* ^ last_offset
*/
}

/* check if we are resuming an OUT skb */
if (ctx->tx_curr_skb != NULL) {
/* pop variables */
skb_out = ctx->tx_curr_skb;
offset = ctx->tx_curr_offset;
last_offset = ctx->tx_curr_last_offset;
n = ctx->tx_curr_frame_num;
skb_out = ctx->tx_curr_skb;

} else {
/* reset variables */
/* allocate a new OUT skb */
if (!skb_out) {
skb_out = alloc_skb((ctx->tx_max + 1), GFP_ATOMIC);
if (skb_out == NULL) {
if (skb != NULL) {
Expand All @@ -711,43 +731,36 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
}
goto exit_no_skb;
}
/* fill out the initial 16-bit NTB header */
nth16 = (struct usb_cdc_ncm_nth16 *)memset(skb_put(skb_out, sizeof(struct usb_cdc_ncm_nth16)), 0, sizeof(struct usb_cdc_ncm_nth16));
nth16->dwSignature = cpu_to_le32(USB_CDC_NCM_NTH16_SIGN);
nth16->wHeaderLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16));
nth16->wSequence = cpu_to_le16(ctx->tx_seq++);

/* make room for NTH and NDP */
offset = ALIGN(sizeof(struct usb_cdc_ncm_nth16),
ctx->tx_ndp_modulus) +
sizeof(struct usb_cdc_ncm_ndp16) +
(ctx->tx_max_datagrams + 1) *
sizeof(struct usb_cdc_ncm_dpe16);

/* store last valid offset before alignment */
last_offset = offset;
/* align first Datagram offset correctly */
offset = ALIGN(offset, ctx->tx_modulus) + ctx->tx_remainder;
/* zero buffer till the first IP datagram */
cdc_ncm_zero_fill(skb_out->data, 0, offset, offset);
n = 0;
/* count total number of frames in this NTB */
ctx->tx_curr_frame_num = 0;
}

for (; n < ctx->tx_max_datagrams; n++) {
/* check if end of transmit buffer is reached */
if (offset >= ctx->tx_max) {
ready2send = 1;
break;
}
/* compute maximum buffer size */
rem = ctx->tx_max - offset;

for (n = ctx->tx_curr_frame_num; n < ctx->tx_max_datagrams; n++) {
/* send any remaining skb first */
if (skb == NULL) {
skb = ctx->tx_rem_skb;
sign = ctx->tx_rem_sign;
ctx->tx_rem_skb = NULL;

/* check for end of skb */
if (skb == NULL)
break;
}

if (skb->len > rem) {
/* get the appropriate NDP for this skb */
ndp16 = cdc_ncm_ndp(ctx, skb_out, sign, skb->len + ctx->tx_modulus + ctx->tx_remainder);

/* align beginning of next frame */
cdc_ncm_align_tail(skb_out, ctx->tx_modulus, ctx->tx_remainder, ctx->tx_max);

/* check if we had enough room left for both NDP and frame */
if (!ndp16 || skb_out->len + skb->len > ctx->tx_max) {
if (n == 0) {
/* won't fit, MTU problem? */
dev_kfree_skb_any(skb);
Expand All @@ -760,31 +773,30 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
ctx->netdev->stats.tx_dropped++;
}
ctx->tx_rem_skb = skb;
ctx->tx_rem_sign = sign;
skb = NULL;
ready2send = 1;
}
break;
}

memcpy(((u8 *)skb_out->data) + offset, skb->data, skb->len);

ctx->tx_ncm.dpe16[n].wDatagramLength = cpu_to_le16(skb->len);
ctx->tx_ncm.dpe16[n].wDatagramIndex = cpu_to_le16(offset);

/* update offset */
offset += skb->len;
/* calculate frame number withing this NDP */
ndplen = le16_to_cpu(ndp16->wLength);
index = (ndplen - sizeof(struct usb_cdc_ncm_ndp16)) / sizeof(struct usb_cdc_ncm_dpe16) - 1;

/* store last valid offset before alignment */
last_offset = offset;

/* align offset correctly */
offset = ALIGN(offset, ctx->tx_modulus) + ctx->tx_remainder;

/* zero padding */
cdc_ncm_zero_fill(skb_out->data, last_offset, offset,
ctx->tx_max);
/* OK, add this skb */
ndp16->dpe16[index].wDatagramLength = cpu_to_le16(skb->len);
ndp16->dpe16[index].wDatagramIndex = cpu_to_le16(skb_out->len);
ndp16->wLength = cpu_to_le16(ndplen + sizeof(struct usb_cdc_ncm_dpe16));
memcpy(skb_put(skb_out, skb->len), skb->data, skb->len);
dev_kfree_skb_any(skb);
skb = NULL;

/* send now if this NDP is full */
if (index >= CDC_NCM_DPT_DATAGRAMS_MAX) {
ready2send = 1;
break;
}
}

/* free up any dangling skb */
Expand All @@ -800,16 +812,12 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
/* wait for more frames */
/* push variables */
ctx->tx_curr_skb = skb_out;
ctx->tx_curr_offset = offset;
ctx->tx_curr_last_offset = last_offset;
goto exit_no_skb;

} else if ((n < ctx->tx_max_datagrams) && (ready2send == 0)) {
/* wait for more frames */
/* push variables */
ctx->tx_curr_skb = skb_out;
ctx->tx_curr_offset = offset;
ctx->tx_curr_last_offset = last_offset;
/* set the pending count */
if (n < CDC_NCM_RESTART_TIMER_DATAGRAM_CNT)
ctx->tx_timer_pending = CDC_NCM_TIMER_PENDING_CNT;
Expand All @@ -820,75 +828,24 @@ cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb)
/* variables will be reset at next call */
}

/* check for overflow */
if (last_offset > ctx->tx_max)
last_offset = ctx->tx_max;

/* revert offset */
offset = last_offset;

/*
* If collected data size is less or equal CDC_NCM_MIN_TX_PKT bytes,
* we send buffers as it is. If we get more data, it would be more
* efficient for USB HS mobile device with DMA engine to receive a full
* size NTB, than canceling DMA transfer and receiving a short packet.
*/
if (offset > CDC_NCM_MIN_TX_PKT)
offset = ctx->tx_max;

/* final zero padding */
cdc_ncm_zero_fill(skb_out->data, last_offset, offset, ctx->tx_max);

/* store last offset */
last_offset = offset;

if (((last_offset < ctx->tx_max) && ((last_offset %
le16_to_cpu(ctx->out_ep->desc.wMaxPacketSize)) == 0)) ||
(((last_offset == ctx->tx_max) && ((ctx->tx_max %
le16_to_cpu(ctx->out_ep->desc.wMaxPacketSize)) == 0)) &&
(ctx->tx_max < le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize)))) {
/* force short packet */
*(((u8 *)skb_out->data) + last_offset) = 0;
last_offset++;
}
if (skb_out->len > CDC_NCM_MIN_TX_PKT)
/* final zero padding */
memset(skb_put(skb_out, ctx->tx_max - skb_out->len), 0, ctx->tx_max - skb_out->len);

/* zero the rest of the DPEs plus the last NULL entry */
for (; n <= CDC_NCM_DPT_DATAGRAMS_MAX; n++) {
ctx->tx_ncm.dpe16[n].wDatagramLength = 0;
ctx->tx_ncm.dpe16[n].wDatagramIndex = 0;
}

/* fill out 16-bit NTB header */
ctx->tx_ncm.nth16.dwSignature = cpu_to_le32(USB_CDC_NCM_NTH16_SIGN);
ctx->tx_ncm.nth16.wHeaderLength =
cpu_to_le16(sizeof(ctx->tx_ncm.nth16));
ctx->tx_ncm.nth16.wSequence = cpu_to_le16(ctx->tx_seq);
ctx->tx_ncm.nth16.wBlockLength = cpu_to_le16(last_offset);
index = ALIGN(sizeof(struct usb_cdc_ncm_nth16), ctx->tx_ndp_modulus);
ctx->tx_ncm.nth16.wNdpIndex = cpu_to_le16(index);

memcpy(skb_out->data, &(ctx->tx_ncm.nth16), sizeof(ctx->tx_ncm.nth16));
ctx->tx_seq++;

/* fill out 16-bit NDP table */
ctx->tx_ncm.ndp16.dwSignature =
cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN);
rem = sizeof(ctx->tx_ncm.ndp16) + ((ctx->tx_curr_frame_num + 1) *
sizeof(struct usb_cdc_ncm_dpe16));
ctx->tx_ncm.ndp16.wLength = cpu_to_le16(rem);
ctx->tx_ncm.ndp16.wNextNdpIndex = 0; /* reserved */

memcpy(((u8 *)skb_out->data) + index,
&(ctx->tx_ncm.ndp16),
sizeof(ctx->tx_ncm.ndp16));

memcpy(((u8 *)skb_out->data) + index + sizeof(ctx->tx_ncm.ndp16),
&(ctx->tx_ncm.dpe16),
(ctx->tx_curr_frame_num + 1) *
sizeof(struct usb_cdc_ncm_dpe16));
/* do we need to prevent a ZLP? */
if (((skb_out->len % le16_to_cpu(ctx->out_ep->desc.wMaxPacketSize)) == 0) &&
(skb_out->len < le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize)) && skb_tailroom(skb_out))
*skb_put(skb_out, 1) = 0; /* force short packet */

/* set frame length */
skb_put(skb_out, last_offset);
/* set final frame length */
nth16 = (struct usb_cdc_ncm_nth16 *)skb_out->data;
nth16->wBlockLength = cpu_to_le16(skb_out->len);

/* return skb */
ctx->tx_curr_skb = NULL;
Expand Down Expand Up @@ -955,7 +912,7 @@ cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
goto error;

spin_lock_bh(&ctx->mtx);
skb_out = cdc_ncm_fill_tx_frame(ctx, skb);
skb_out = cdc_ncm_fill_tx_frame(ctx, skb, cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN));
spin_unlock_bh(&ctx->mtx);
return skb_out;

Expand Down

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