2011-04-19 00:32:07

by Linus Walleij

Subject: [PATCH] dmaengine: implement pause and resume for dw_dmac

It seems that the SPEAr needs this.

Signed-off-by: Linus Walleij <[email protected]>
---
drivers/dma/dw_dmac.c | 22 ++++++++++++++++++++--
drivers/dma/dw_dmac_regs.h | 1 +
2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 9c25c7d..60ac779 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -801,8 +801,7 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
struct dw_desc *desc, *_desc;
LIST_HEAD(list);

- /* Only supports DMA_TERMINATE_ALL */
- if (cmd != DMA_TERMINATE_ALL)
+ if (cmd != DMA_TERMINATE_ALL && cmd != DMA_PAUSE && cmd != DMA_RESUME)
return -ENXIO;

/*
@@ -813,11 +812,30 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
*/
spin_lock_bh(&dwc->lock);

+ if (cmd == DMA_RESUME) {
+ if (dwc->paused) {
+ channel_set_bit(dw, CH_EN, dwc->mask);
+ while (!dma_readl(dw, CH_EN) & dwc->mask)
+ cpu_relax();
+ }
+ spin_unlock_bh(&dwc->lock);
+ return 0;
+ }
+
channel_clear_bit(dw, CH_EN, dwc->mask);

while (dma_readl(dw, CH_EN) & dwc->mask)
cpu_relax();

+ if (cmd == DMA_PAUSE) {
+ dwc->paused = true;
+ spin_unlock_bh(&dwc->lock);
+ return 0;
+ }
+
+ /* Terminating a paused transfer */
+ 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);
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;

--
1.7.4

2011-04-19 05:29:49

by Viresh Kumar

Subject: Re: [PATCH] dmaengine: implement pause and resume for dw_dmac

On 04/19/2011 06:01 AM, Linus Walleij wrote:
> It seems that the SPEAr needs this.
>
> Signed-off-by: Linus Walleij <[email protected]>

Thanks for sending this.
Actually i wasn't sure that disabling channel will simply pause it, and not
finish the transfer. So, didn't went for this change.

> ---
> drivers/dma/dw_dmac.c | 22 ++++++++++++++++++++--
> drivers/dma/dw_dmac_regs.h | 1 +
> 2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
> index 9c25c7d..60ac779 100644
> --- a/drivers/dma/dw_dmac.c
> +++ b/drivers/dma/dw_dmac.c
> @@ -801,8 +801,7 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> struct dw_desc *desc, *_desc;
> LIST_HEAD(list);
>
> - /* Only supports DMA_TERMINATE_ALL */
> - if (cmd != DMA_TERMINATE_ALL)
> + if (cmd != DMA_TERMINATE_ALL && cmd != DMA_PAUSE && cmd != DMA_RESUME)
> return -ENXIO;
>
> /*
> @@ -813,11 +812,30 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> */
> spin_lock_bh(&dwc->lock);
>
> + if (cmd == DMA_RESUME) {
> + if (dwc->paused) {
> + channel_set_bit(dw, CH_EN, dwc->mask);
> + while (!dma_readl(dw, CH_EN) & dwc->mask)

Probably should be written as
while (!(dma_readl(dw, CH_EN) & dwc->mask))

> + cpu_relax();
> + }

Should return error in else part??

> + spin_unlock_bh(&dwc->lock);
> + return 0;
> + }
> +
> channel_clear_bit(dw, CH_EN, dwc->mask);
>
> while (dma_readl(dw, CH_EN) & dwc->mask)
> cpu_relax();
>
> + if (cmd == DMA_PAUSE) {
> + dwc->paused = true;
> + spin_unlock_bh(&dwc->lock);

I have sent another patchset in which _bh variants are replaced with irqsave
variants. To remove any conflicts, i would add your patch in my patchset, with
above mentioned changes keeping your authorship intact.

Will that be fine??

--
viresh

2011-04-19 06:04:53

by Viresh Kumar

Subject: Re: [PATCH] dmaengine: implement pause and resume for dw_dmac

On 04/19/2011 10:59 AM, viresh kumar wrote:
> On 04/19/2011 06:01 AM, Linus Walleij wrote:
>> > It seems that the SPEAr needs this.
>> >
>> > Signed-off-by: Linus Walleij <[email protected]>
> Thanks for sending this.
> Actually i wasn't sure that disabling channel will simply pause it, and not
> finish the transfer. So, didn't went for this change.
>
>> > ---
>> > drivers/dma/dw_dmac.c | 22 ++++++++++++++++++++--
>> > drivers/dma/dw_dmac_regs.h | 1 +
>> > 2 files changed, 21 insertions(+), 2 deletions(-)

Moreover, dwc_tx_status() must be updated to add following code:

if (dwc->paused)
return DMA_PAUSED;

Will do that while sending it in my patchset.

--
viresh