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drivers/rapidio/devices/tsi721_dma.c: optimize use of BDMA descriptors
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Combine SG entries describing single contiguous memory block into one
Tsi721 BDMA descriptor.  This reduces number of hardware descriptors
required for large data transfers and improves performance on the PCIe
side by reducing number of descriptor fetch requests.

Signed-off-by: Alexandre Bounine <[email protected]>
Cc: Matt Porter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Alexandre Bounine authored and torvalds committed Apr 7, 2014
1 parent 3f59b06 commit 40f847b
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Showing 2 changed files with 82 additions and 33 deletions.
4 changes: 4 additions & 0 deletions drivers/rapidio/devices/tsi721.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -644,6 +644,9 @@ enum tsi721_smsg_int_flag {

#ifdef CONFIG_RAPIDIO_DMA_ENGINE

#define TSI721_BDMA_BD_RING_SZ 128
#define TSI721_BDMA_MAX_BCOUNT (TSI721_DMAD_BCOUNT1 + 1)

struct tsi721_tx_desc {
struct dma_async_tx_descriptor txd;
struct tsi721_dma_desc *hw_desc;
Expand All @@ -652,6 +655,7 @@ struct tsi721_tx_desc {
u64 rio_addr;
/* upper 2-bits of 66-bit RIO address */
u8 rio_addr_u;
u32 bcount;
bool interrupt;
struct list_head desc_node;
struct list_head tx_list;
Expand Down
111 changes: 78 additions & 33 deletions drivers/rapidio/devices/tsi721_dma.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -304,35 +304,17 @@ struct tsi721_tx_desc *tsi721_desc_get(struct tsi721_bdma_chan *bdma_chan)
}

static int
tsi721_fill_desc(struct tsi721_bdma_chan *bdma_chan,
struct tsi721_tx_desc *desc, struct scatterlist *sg,
tsi721_desc_fill_init(struct tsi721_tx_desc *desc, struct scatterlist *sg,
enum dma_rtype rtype, u32 sys_size)
{
struct tsi721_dma_desc *bd_ptr = desc->hw_desc;
u64 rio_addr;

if (sg_dma_len(sg) > TSI721_DMAD_BCOUNT1 + 1) {
dev_err(bdma_chan->dchan.device->dev,
"SG element is too large\n");
return -EINVAL;
}

dev_dbg(bdma_chan->dchan.device->dev,
"desc: 0x%llx, addr: 0x%llx len: 0x%x\n",
(u64)desc->txd.phys, (unsigned long long)sg_dma_address(sg),
sg_dma_len(sg));

dev_dbg(bdma_chan->dchan.device->dev,
"bd_ptr = %p did=%d raddr=0x%llx\n",
bd_ptr, desc->destid, desc->rio_addr);

/* Initialize DMA descriptor */
bd_ptr->type_id = cpu_to_le32((DTYPE1 << 29) |
(rtype << 19) | desc->destid);
if (desc->interrupt)
bd_ptr->type_id |= cpu_to_le32(TSI721_DMAD_IOF);
bd_ptr->bcount = cpu_to_le32(((desc->rio_addr & 0x3) << 30) |
(sys_size << 26) | sg_dma_len(sg));
(sys_size << 26));
rio_addr = (desc->rio_addr >> 2) |
((u64)(desc->rio_addr_u & 0x3) << 62);
bd_ptr->raddr_lo = cpu_to_le32(rio_addr & 0xffffffff);
Expand All @@ -346,6 +328,20 @@ tsi721_fill_desc(struct tsi721_bdma_chan *bdma_chan,
return 0;
}

static int
tsi721_desc_fill_end(struct tsi721_tx_desc *desc)
{
struct tsi721_dma_desc *bd_ptr = desc->hw_desc;

/* Update DMA descriptor */
if (desc->interrupt)
bd_ptr->type_id |= cpu_to_le32(TSI721_DMAD_IOF);
bd_ptr->bcount |= cpu_to_le32(desc->bcount & TSI721_DMAD_BCOUNT1);

return 0;
}


static void tsi721_dma_chain_complete(struct tsi721_bdma_chan *bdma_chan,
struct tsi721_tx_desc *desc)
{
Expand Down Expand Up @@ -674,6 +670,7 @@ struct dma_async_tx_descriptor *tsi721_prep_rio_sg(struct dma_chan *dchan,
unsigned int i;
u32 sys_size = dma_to_mport(dchan->device)->sys_size;
enum dma_rtype rtype;
dma_addr_t next_addr = -1;

if (!sgl || !sg_len) {
dev_err(dchan->device->dev, "%s: No SG list\n", __func__);
Expand Down Expand Up @@ -704,44 +701,92 @@ struct dma_async_tx_descriptor *tsi721_prep_rio_sg(struct dma_chan *dchan,
for_each_sg(sgl, sg, sg_len, i) {
int err;

dev_dbg(dchan->device->dev, "%s: sg #%d\n", __func__, i);
if (sg_dma_len(sg) > TSI721_BDMA_MAX_BCOUNT) {
dev_err(dchan->device->dev,
"%s: SG entry %d is too large\n", __func__, i);
goto err_desc_put;
}

/*
* If this sg entry forms contiguous block with previous one,
* try to merge it into existing DMA descriptor
*/
if (desc) {
if (next_addr == sg_dma_address(sg) &&
desc->bcount + sg_dma_len(sg) <=
TSI721_BDMA_MAX_BCOUNT) {
/* Adjust byte count of the descriptor */
desc->bcount += sg_dma_len(sg);
goto entry_done;
}

/*
* Finalize this descriptor using total
* byte count value.
*/
tsi721_desc_fill_end(desc);
dev_dbg(dchan->device->dev, "%s: desc final len: %d\n",
__func__, desc->bcount);
}

/*
* Obtain and initialize a new descriptor
*/
desc = tsi721_desc_get(bdma_chan);
if (!desc) {
dev_err(dchan->device->dev,
"Not enough descriptors available\n");
goto err_desc_get;
"%s: Failed to get new descriptor for SG %d\n",
__func__, i);
goto err_desc_put;
}

if (sg_is_last(sg))
desc->interrupt = (flags & DMA_PREP_INTERRUPT) != 0;
else
desc->interrupt = false;

desc->destid = rext->destid;
desc->rio_addr = rio_addr;
desc->rio_addr_u = 0;
desc->bcount = sg_dma_len(sg);

dev_dbg(dchan->device->dev,
"sg%d desc: 0x%llx, addr: 0x%llx len: %d\n",
i, (u64)desc->txd.phys,
(unsigned long long)sg_dma_address(sg),
sg_dma_len(sg));

dev_dbg(dchan->device->dev,
"bd_ptr = %p did=%d raddr=0x%llx\n",
desc->hw_desc, desc->destid, desc->rio_addr);

err = tsi721_fill_desc(bdma_chan, desc, sg, rtype, sys_size);
err = tsi721_desc_fill_init(desc, sg, rtype, sys_size);
if (err) {
dev_err(dchan->device->dev,
"Failed to build desc: %d\n", err);
goto err_desc_get;
goto err_desc_put;
}

rio_addr += sg_dma_len(sg);
next_addr = sg_dma_address(sg);

if (!first)
first = desc;
else
list_add_tail(&desc->desc_node, &first->tx_list);

entry_done:
if (sg_is_last(sg)) {
desc->interrupt = (flags & DMA_PREP_INTERRUPT) != 0;
tsi721_desc_fill_end(desc);
dev_dbg(dchan->device->dev, "%s: desc final len: %d\n",
__func__, desc->bcount);
} else {
rio_addr += sg_dma_len(sg);
next_addr += sg_dma_len(sg);
}
}

first->txd.cookie = -EBUSY;
desc->txd.flags = flags;

return &first->txd;

err_desc_get:
err_desc_put:
tsi721_desc_put(bdma_chan, first);
return NULL;
}
Expand Down Expand Up @@ -792,7 +837,7 @@ int tsi721_register_dma(struct tsi721_device *priv)
if (i == TSI721_DMACH_MAINT)
continue;

bdma_chan->bd_num = 64;
bdma_chan->bd_num = TSI721_BDMA_BD_RING_SZ;
bdma_chan->regs = priv->regs + TSI721_DMAC_BASE(i);

bdma_chan->dchan.device = &mport->dma;
Expand Down

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