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dw_dmac: introduce software emulation of LLP transfers

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Some controllers have the reduced functionality where the LLP multi block
transfers are not supported. This patch introduces a support of such
controllers. In case of memory copy or scatter-gather lists it emulates LLP
transfers via bunch of the regular single block ones.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
This commit is contained in:
Andy Shevchenko 2012-09-21 15:05:49 +03:00 committed by Vinod Koul
parent a09820043c
commit fed2574b3c
2 changed files with 101 additions and 4 deletions
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99
drivers/dma/dw_dmac.c
View file

@ -232,10 +232,29 @@ static inline void dwc_chan_disable(struct dw_dma *dw, struct dw_dma_chan *dwc)
/*----------------------------------------------------------------------*/
/* Perform single block transfer */
static inline void dwc_do_single_block(struct dw_dma_chan *dwc,
struct dw_desc *desc)
{
struct dw_dma *dw = to_dw_dma(dwc->chan.device);
u32 ctllo;
/* Software emulation of LLP mode relies on interrupts to continue
* multi block transfer. */
ctllo = desc->lli.ctllo | DWC_CTLL_INT_EN;
channel_writel(dwc, SAR, desc->lli.sar);
channel_writel(dwc, DAR, desc->lli.dar);
channel_writel(dwc, CTL_LO, ctllo);
channel_writel(dwc, CTL_HI, desc->lli.ctlhi);
channel_set_bit(dw, CH_EN, dwc->mask);
}
/* Called with dwc->lock held and bh disabled */
static void dwc_dostart(struct dw_dma_chan *dwc, struct dw_desc *first)
{
struct dw_dma *dw = to_dw_dma(dwc->chan.device);
unsigned long was_soft_llp;
/* ASSERT: channel is idle */
if (dma_readl(dw, CH_EN) & dwc->mask) {
@ -247,6 +266,26 @@ static void dwc_dostart(struct dw_dma_chan *dwc, struct dw_desc *first)
return;
}
if (dwc->nollp) {
was_soft_llp = test_and_set_bit(DW_DMA_IS_SOFT_LLP,
&dwc->flags);
if (was_soft_llp) {
dev_err(chan2dev(&dwc->chan),
"BUG: Attempted to start new LLP transfer "
"inside ongoing one\n");
return;
}
dwc_initialize(dwc);
dwc->tx_list = &first->tx_list;
dwc->tx_node_active = first->tx_list.next;
dwc_do_single_block(dwc, first);
return;
}
dwc_initialize(dwc);
channel_writel(dwc, LLP, first->txd.phys);
@ -558,8 +597,36 @@ static void dw_dma_tasklet(unsigned long data)
dwc_handle_cyclic(dw, dwc, status_err, status_xfer);
else if (status_err & (1 << i))
dwc_handle_error(dw, dwc);
else if (status_xfer & (1 << i))
else if (status_xfer & (1 << i)) {
unsigned long flags;
spin_lock_irqsave(&dwc->lock, flags);
if (test_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags)) {
if (dwc->tx_node_active != dwc->tx_list) {
struct dw_desc *desc =
list_entry(dwc->tx_node_active,
struct dw_desc,
desc_node);
dma_writel(dw, CLEAR.XFER, dwc->mask);
/* move pointer to next descriptor */
dwc->tx_node_active =
dwc->tx_node_active->next;
dwc_do_single_block(dwc, desc);
spin_unlock_irqrestore(&dwc->lock, flags);
continue;
} else {
/* we are done here */
clear_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags);
}
}
spin_unlock_irqrestore(&dwc->lock, flags);
dwc_scan_descriptors(dw, dwc);
}
}
/*
@ -962,6 +1029,8 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
} else if (cmd == DMA_TERMINATE_ALL) {
spin_lock_irqsave(&dwc->lock, flags);
clear_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags);
dwc_chan_disable(dw, dwc);
dwc->paused = false;
@ -1204,6 +1273,13 @@ struct dw_cyclic_desc *dw_dma_cyclic_prep(struct dma_chan *chan,
unsigned long flags;
spin_lock_irqsave(&dwc->lock, flags);
if (dwc->nollp) {
spin_unlock_irqrestore(&dwc->lock, flags);
dev_dbg(chan2dev(&dwc->chan),
"channel doesn't support LLP transfers\n");
return ERR_PTR(-EINVAL);
}
if (!list_empty(&dwc->queue) || !list_empty(&dwc->active_list)) {
spin_unlock_irqrestore(&dwc->lock, flags);
dev_dbg(chan2dev(&dwc->chan),
@ -1471,6 +1547,7 @@ static int __devinit dw_probe(struct platform_device *pdev)
INIT_LIST_HEAD(&dw->dma.channels);
for (i = 0; i < nr_channels; i++) {
struct dw_dma_chan *dwc = &dw->chan[i];
int r = nr_channels - i - 1;
dwc->chan.device = &dw->dma;
dma_cookie_init(&dwc->chan);
@ -1482,7 +1559,7 @@ static int __devinit dw_probe(struct platform_device *pdev)
/* 7 is highest priority & 0 is lowest. */
if (pdata->chan_priority == CHAN_PRIORITY_ASCENDING)
dwc->priority = nr_channels - i - 1;
dwc->priority = r;
else
dwc->priority = i;
@ -1499,14 +1576,28 @@ static int __devinit dw_probe(struct platform_device *pdev)
dwc->dw = dw;
/* hardware configuration */
if (autocfg)
if (autocfg) {
unsigned int dwc_params;
dwc_params = dma_read_byaddr(regs + r * sizeof(u32),
DWC_PARAMS);
/* Decode maximum block size for given channel. The
* stored 4 bit value represents blocks from 0x00 for 3
* up to 0x0a for 4095. */
dwc->block_size =
(4 << ((max_blk_size >> 4 * i) & 0xf)) - 1;
else
dwc->nollp =
(dwc_params >> DWC_PARAMS_MBLK_EN & 0x1) == 0;
} else {
dwc->block_size = pdata->block_size;
/* Check if channel supports multi block transfer */
channel_writel(dwc, LLP, 0xfffffffc);
dwc->nollp =
(channel_readl(dwc, LLP) & 0xfffffffc) == 0;
channel_writel(dwc, LLP, 0);
}
}
/* Clear all interrupts on all channels. */

6
drivers/dma/dw_dmac_regs.h
View file

@ -172,6 +172,7 @@ struct dw_dma_regs {
enum dw_dmac_flags {
DW_DMA_IS_CYCLIC = 0,
DW_DMA_IS_SOFT_LLP = 1,
};
struct dw_dma_chan {
@ -182,6 +183,10 @@ struct dw_dma_chan {
bool paused;
bool initialized;
/* software emulation of the LLP transfers */
struct list_head *tx_list;
struct list_head *tx_node_active;
spinlock_t lock;
/* these other elements are all protected by lock */
@ -195,6 +200,7 @@ struct dw_dma_chan {
/* hardware configuration */
unsigned int block_size;
bool nollp;
/* configuration passed via DMA_SLAVE_CONFIG */
struct dma_slave_config dma_sconfig;