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sh: prepare the DMA driver for slave functionality
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Slave DMA functionality uses scatter-gather arrays for data transfers,
whereas memcpy just uses a single data buffer. This patch converts the
current memcpy implementation in shdma.c to use scatter-gather, making it
just a special case with one SG-element. This allows us to isolate
descriptor list manipulations and locking into one function, thus reducing
error chances.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
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Guennadi Liakhovetski authored and Paul Mundt committed Feb 8, 2010
1 parent 6339204 commit fc46185
Showing 1 changed file with 153 additions and 68 deletions.
221 changes: 153 additions & 68 deletions drivers/dma/shdma.c
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Original file line number Diff line number Diff line change
Expand Up @@ -53,12 +53,12 @@ static void sh_dmae_chan_ld_cleanup(struct sh_dmae_chan *sh_chan, bool all);
#define SH_DMAC_CHAN_BASE(id) (dma_base_addr[id])
static void sh_dmae_writel(struct sh_dmae_chan *sh_dc, u32 data, u32 reg)
{
ctrl_outl(data, (SH_DMAC_CHAN_BASE(sh_dc->id) + reg));
ctrl_outl(data, SH_DMAC_CHAN_BASE(sh_dc->id) + reg);
}

static u32 sh_dmae_readl(struct sh_dmae_chan *sh_dc, u32 reg)
{
return ctrl_inl((SH_DMAC_CHAN_BASE(sh_dc->id) + reg));
return ctrl_inl(SH_DMAC_CHAN_BASE(sh_dc->id) + reg);
}

static void dmae_init(struct sh_dmae_chan *sh_chan)
Expand Down Expand Up @@ -95,14 +95,14 @@ static int sh_dmae_rst(int id)
return 0;
}

static int dmae_is_busy(struct sh_dmae_chan *sh_chan)
static bool dmae_is_busy(struct sh_dmae_chan *sh_chan)
{
u32 chcr = sh_dmae_readl(sh_chan, CHCR);
if (chcr & CHCR_DE) {
if (!(chcr & CHCR_TE))
return -EBUSY; /* working */
}
return 0; /* waiting */

if ((chcr & (CHCR_DE | CHCR_TE)) == CHCR_DE)
return true; /* working */

return false; /* waiting */
}

static inline unsigned int calc_xmit_shift(struct sh_dmae_chan *sh_chan)
Expand Down Expand Up @@ -136,10 +136,9 @@ static void dmae_halt(struct sh_dmae_chan *sh_chan)

static int dmae_set_chcr(struct sh_dmae_chan *sh_chan, u32 val)
{
int ret = dmae_is_busy(sh_chan);
/* When DMA was working, can not set data to CHCR */
if (ret)
return ret;
if (dmae_is_busy(sh_chan))
return -EBUSY;

sh_dmae_writel(sh_chan, val, CHCR);
return 0;
Expand All @@ -153,9 +152,9 @@ static int dmae_set_dmars(struct sh_dmae_chan *sh_chan, u16 val)
{
u32 addr;
int shift = 0;
int ret = dmae_is_busy(sh_chan);
if (ret)
return ret;

if (dmae_is_busy(sh_chan))
return -EBUSY;

if (sh_chan->id & DMARS_CHAN_MSK)
shift = DMARS_SHIFT;
Expand Down Expand Up @@ -301,23 +300,95 @@ static void sh_dmae_free_chan_resources(struct dma_chan *chan)
kfree(desc);
}

static struct dma_async_tx_descriptor *sh_dmae_prep_memcpy(
struct dma_chan *chan, dma_addr_t dma_dest, dma_addr_t dma_src,
size_t len, unsigned long flags)
/*
* sh_dmae_add_desc - get, set up and return one transfer descriptor
* @sh_chan: DMA channel
* @flags: DMA transfer flags
* @dest: destination DMA address, incremented when direction equals
* DMA_FROM_DEVICE or DMA_BIDIRECTIONAL
* @src: source DMA address, incremented when direction equals
* DMA_TO_DEVICE or DMA_BIDIRECTIONAL
* @len: DMA transfer length
* @first: if NULL, set to the current descriptor and cookie set to -EBUSY
* @direction: needed for slave DMA to decide which address to keep constant,
* equals DMA_BIDIRECTIONAL for MEMCPY
* Returns 0 or an error
* Locks: called with desc_lock held
*/
static struct sh_desc *sh_dmae_add_desc(struct sh_dmae_chan *sh_chan,
unsigned long flags, dma_addr_t *dest, dma_addr_t *src, size_t *len,
struct sh_desc **first, enum dma_data_direction direction)
{
struct sh_dmae_chan *sh_chan;
struct sh_desc *first = NULL, *prev = NULL, *new;
struct sh_desc *new;
size_t copy_size;
LIST_HEAD(tx_list);
int chunks = (len + SH_DMA_TCR_MAX) / (SH_DMA_TCR_MAX + 1);

if (!chan)
if (!*len)
return NULL;

if (!len)
/* Allocate the link descriptor from the free list */
new = sh_dmae_get_desc(sh_chan);
if (!new) {
dev_err(sh_chan->dev, "No free link descriptor available\n");
return NULL;
}

sh_chan = to_sh_chan(chan);
copy_size = min(*len, (size_t)SH_DMA_TCR_MAX + 1);

new->hw.sar = *src;
new->hw.dar = *dest;
new->hw.tcr = copy_size;

if (!*first) {
/* First desc */
new->async_tx.cookie = -EBUSY;
*first = new;
} else {
/* Other desc - invisible to the user */
new->async_tx.cookie = -EINVAL;
}

dev_dbg(sh_chan->dev, "chaining (%u/%u)@%x -> %x with %p, cookie %d\n",
copy_size, *len, *src, *dest, &new->async_tx,
new->async_tx.cookie);

new->mark = DESC_PREPARED;
new->async_tx.flags = flags;

*len -= copy_size;
if (direction == DMA_BIDIRECTIONAL || direction == DMA_TO_DEVICE)
*src += copy_size;
if (direction == DMA_BIDIRECTIONAL || direction == DMA_FROM_DEVICE)
*dest += copy_size;

return new;
}

/*
* sh_dmae_prep_sg - prepare transfer descriptors from an SG list
*
* Common routine for public (MEMCPY) and slave DMA. The MEMCPY case is also
* converted to scatter-gather to guarantee consistent locking and a correct
* list manipulation. For slave DMA direction carries the usual meaning, and,
* logically, the SG list is RAM and the addr variable contains slave address,
* e.g., the FIFO I/O register. For MEMCPY direction equals DMA_BIDIRECTIONAL
* and the SG list contains only one element and points at the source buffer.
*/
static struct dma_async_tx_descriptor *sh_dmae_prep_sg(struct sh_dmae_chan *sh_chan,
struct scatterlist *sgl, unsigned int sg_len, dma_addr_t *addr,
enum dma_data_direction direction, unsigned long flags)
{
struct scatterlist *sg;
struct sh_desc *first = NULL, *new = NULL /* compiler... */;
LIST_HEAD(tx_list);
int chunks = 0;
int i;

if (!sg_len)
return NULL;

for_each_sg(sgl, sg, sg_len, i)
chunks += (sg_dma_len(sg) + SH_DMA_TCR_MAX) /
(SH_DMA_TCR_MAX + 1);

/* Have to lock the whole loop to protect against concurrent release */
spin_lock_bh(&sh_chan->desc_lock);
Expand All @@ -333,49 +404,32 @@ static struct dma_async_tx_descriptor *sh_dmae_prep_memcpy(
* only during this function, then they are immediately spliced
* back onto the free list in form of a chain
*/
do {
/* Allocate the link descriptor from the free list */
new = sh_dmae_get_desc(sh_chan);
if (!new) {
dev_err(sh_chan->dev,
"No free memory for link descriptor\n");
list_for_each_entry(new, &tx_list, node)
new->mark = DESC_IDLE;
list_splice(&tx_list, &sh_chan->ld_free);
spin_unlock_bh(&sh_chan->desc_lock);
return NULL;
}

copy_size = min(len, (size_t)SH_DMA_TCR_MAX + 1);

new->hw.sar = dma_src;
new->hw.dar = dma_dest;
new->hw.tcr = copy_size;
if (!first) {
/* First desc */
new->async_tx.cookie = -EBUSY;
first = new;
} else {
/* Other desc - invisible to the user */
new->async_tx.cookie = -EINVAL;
}

dev_dbg(sh_chan->dev,
"chaining %u of %u with %p, dst %x, cookie %d\n",
copy_size, len, &new->async_tx, dma_dest,
new->async_tx.cookie);

new->mark = DESC_PREPARED;
new->async_tx.flags = flags;
new->chunks = chunks--;

prev = new;
len -= copy_size;
dma_src += copy_size;
dma_dest += copy_size;
/* Insert the link descriptor to the LD ring */
list_add_tail(&new->node, &tx_list);
} while (len);
for_each_sg(sgl, sg, sg_len, i) {
dma_addr_t sg_addr = sg_dma_address(sg);
size_t len = sg_dma_len(sg);

if (!len)
goto err_get_desc;

do {
dev_dbg(sh_chan->dev, "Add SG #%d@%p[%d], dma %llx\n",
i, sg, len, (unsigned long long)sg_addr);

if (direction == DMA_FROM_DEVICE)
new = sh_dmae_add_desc(sh_chan, flags,
&sg_addr, addr, &len, &first,
direction);
else
new = sh_dmae_add_desc(sh_chan, flags,
addr, &sg_addr, &len, &first,
direction);
if (!new)
goto err_get_desc;

new->chunks = chunks--;
list_add_tail(&new->node, &tx_list);
} while (len);
}

if (new != first)
new->async_tx.cookie = -ENOSPC;
Expand All @@ -386,6 +440,37 @@ static struct dma_async_tx_descriptor *sh_dmae_prep_memcpy(
spin_unlock_bh(&sh_chan->desc_lock);

return &first->async_tx;

err_get_desc:
list_for_each_entry(new, &tx_list, node)
new->mark = DESC_IDLE;
list_splice(&tx_list, &sh_chan->ld_free);

spin_unlock_bh(&sh_chan->desc_lock);

return NULL;
}

static struct dma_async_tx_descriptor *sh_dmae_prep_memcpy(
struct dma_chan *chan, dma_addr_t dma_dest, dma_addr_t dma_src,
size_t len, unsigned long flags)
{
struct sh_dmae_chan *sh_chan;
struct scatterlist sg;

if (!chan || !len)
return NULL;

sh_chan = to_sh_chan(chan);

sg_init_table(&sg, 1);
sg_set_page(&sg, pfn_to_page(PFN_DOWN(dma_src)), len,
offset_in_page(dma_src));
sg_dma_address(&sg) = dma_src;
sg_dma_len(&sg) = len;

return sh_dmae_prep_sg(sh_chan, &sg, 1, &dma_dest, DMA_BIDIRECTIONAL,
flags);
}

static dma_async_tx_callback __ld_cleanup(struct sh_dmae_chan *sh_chan, bool all)
Expand Down Expand Up @@ -559,7 +644,7 @@ static irqreturn_t sh_dmae_err(int irq, void *data)

/* IRQ Multi */
if (shdev->pdata.mode & SHDMA_MIX_IRQ) {
int cnt = 0;
int __maybe_unused cnt = 0;
switch (irq) {
#if defined(DMTE6_IRQ) && defined(DMAE1_IRQ)
case DMTE6_IRQ:
Expand Down

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