[PATCH V5 5/5] dmaengine/dw_dmac: implement pause and resume in dwc_control

From: Viresh Kumar
Date: Mon May 09 2011 - 04:16:39 EST


From: Linus Walleij <linus.walleij@xxxxxxxxxx>

Some peripherals like amba-pl011 needs pause to be implemented in DMA controller
drivers. This also returns correct status from dwc_tx_status() in case chan is
paused.

Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxx>
---
drivers/dma/dw_dmac.c | 59 +++++++++++++++++++++++++++++---------------
drivers/dma/dw_dmac_regs.h | 1 +
2 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 1a3fe3e..d83fd24 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -862,34 +862,50 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
struct dw_dma *dw = to_dw_dma(chan->device);
struct dw_desc *desc, *_desc;
unsigned long flags;
+ u32 cfglo;
LIST_HEAD(list);

- /* Only supports DMA_TERMINATE_ALL */
- if (cmd != DMA_TERMINATE_ALL)
- return -ENXIO;
+ if (cmd == DMA_PAUSE) {
+ spin_lock_irqsave(&dwc->lock, flags);

- /*
- * This is only called when something went wrong elsewhere, so
- * we don't really care about the data. Just disable the
- * channel. We still have to poll the channel enable bit due
- * to AHB/HSB limitations.
- */
- spin_lock_irqsave(&dwc->lock, flags);
+ cfglo = channel_readl(dwc, CFG_LO);
+ channel_writel(dwc, CFG_LO, cfglo | DWC_CFGL_CH_SUSP);
+ while (!(channel_readl(dwc, CFG_LO) & DWC_CFGL_FIFO_EMPTY))
+ cpu_relax();

- channel_clear_bit(dw, CH_EN, dwc->mask);
+ dwc->paused = true;
+ spin_unlock_irqrestore(&dwc->lock, flags);
+ } else if (cmd == DMA_RESUME) {
+ if (!dwc->paused)
+ return 0;

- while (dma_readl(dw, CH_EN) & dwc->mask)
- cpu_relax();
+ spin_lock_irqsave(&dwc->lock, flags);

- /* active_list entries will end up before queued entries */
- list_splice_init(&dwc->queue, &list);
- list_splice_init(&dwc->active_list, &list);
+ cfglo = channel_readl(dwc, CFG_LO);
+ channel_writel(dwc, CFG_LO, cfglo & ~DWC_CFGL_CH_SUSP);
+ dwc->paused = false;

- spin_unlock_irqrestore(&dwc->lock, flags);
+ spin_unlock_irqrestore(&dwc->lock, flags);
+ } else if (cmd == DMA_TERMINATE_ALL) {
+ spin_lock_irqsave(&dwc->lock, flags);

- /* Flush all pending and queued descriptors */
- list_for_each_entry_safe(desc, _desc, &list, desc_node)
- dwc_descriptor_complete(dwc, desc, false);
+ channel_clear_bit(dw, CH_EN, dwc->mask);
+ while (dma_readl(dw, CH_EN) & dwc->mask)
+ cpu_relax();
+
+ dwc->paused = false;
+
+ /* active_list entries will end up before queued entries */
+ list_splice_init(&dwc->queue, &list);
+ list_splice_init(&dwc->active_list, &list);
+
+ spin_unlock_irqrestore(&dwc->lock, flags);
+
+ /* Flush all pending and queued descriptors */
+ list_for_each_entry_safe(desc, _desc, &list, desc_node)
+ dwc_descriptor_complete(dwc, desc, false);
+ } else
+ return -ENXIO;

return 0;
}
@@ -923,6 +939,9 @@ dwc_tx_status(struct dma_chan *chan,
else
dma_set_tx_state(txstate, last_complete, last_used, 0);

+ if (dwc->paused)
+ return DMA_PAUSED;
+
return ret;
}

diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h
index 720f821..c968597 100644
--- a/drivers/dma/dw_dmac_regs.h
+++ b/drivers/dma/dw_dmac_regs.h
@@ -138,6 +138,7 @@ struct dw_dma_chan {
void __iomem *ch_regs;
u8 mask;
u8 priority;
+ bool paused;

spinlock_t lock;

--
1.7.2.2

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