[PATCH 2/3] dmaengine: at_hdmac: improve power management routines

[Nicolas Ferre]

On 07/07/2011 04:20 AM, Vinod Koul wrote:
> On Tue, 2011-06-28 at 13:17 +0200, Nicolas Ferre wrote:
>> Save/restore dma controller state across a suspend-resume sequence.
>> The prepare() function will wait for the non-cyclic channels to become idle.
>> It also deals with cyclic operations with the start at next period while
>> resuming.
>>
>> Signed-off-by: Nicolas Ferre<nicolas.ferre at atmel.com>
>> Signed-off-by: Uwe Kleine-König<u.kleine-koenig at pengutronix.de>
>> ---
>>   drivers/dma/at_hdmac.c      |   88 ++++++++++++++++++++++++++++++++++++++++++-
>>   drivers/dma/at_hdmac_regs.h |    7 +++
>>   2 files changed, 94 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
>> index fd87b96..7096adb 100644
>> --- a/drivers/dma/at_hdmac.c
>> +++ b/drivers/dma/at_hdmac.c
>> @@ -1385,27 +1385,113 @@ static void at_dma_shutdown(struct platform_device *pdev)
>>   	clk_disable(atdma->clk);
>>   }
>>
>> +static int at_dma_prepare(struct device *dev)
>> +{
>> +	struct platform_device *pdev = to_platform_device(dev);
>> +	struct at_dma *atdma = platform_get_drvdata(pdev);
>> +	struct dma_chan *chan, *_chan;
>> +
>> +	list_for_each_entry_safe(chan, _chan,&atdma->dma_common.channels,
>> +			device_node) {
>> +		struct at_dma_chan *atchan = to_at_dma_chan(chan);
>> +		/* wait for transaction completion (except in cyclic case) */
>> +		if (atc_chan_is_enabled(atchan)&&
>> +			!test_bit(ATC_IS_CYCLIC,&atchan->status))
>> +			return -EAGAIN;
> pls fix indent here

Fixed by replacement of test_bit() with a wrapper in a patch to come (as 
you suggest hereafter).

>> +	}
>> +	return 0;
>> +}
>> +
>> +static void atc_suspend_cyclic(struct at_dma_chan *atchan)
>> +{
>> +	struct dma_chan	*chan =&atchan->chan_common;
>> +
>> +	/* Channel should be paused by user
>> +	 * do it anyway even if it is not done already */
>> +	if (!test_bit(ATC_IS_PAUSED,&atchan->status)) {
>> +		dev_warn(chan2dev(chan),
>> +		"cyclic channel not paused, should be done by channel user\n");
>> +		atc_control(chan, DMA_PAUSE, 0);
>> +	}
>> +
>> +	/* now preserve additional data for cyclic operations */
>> +	/* next descriptor address in the cyclic list */
>> +	atchan->save_dscr = channel_readl(atchan, DSCR);
>> +
>> +	vdbg_dump_regs(atchan);
>> +}
>> +
>>   static int at_dma_suspend_noirq(struct device *dev)
>>   {
>>   	struct platform_device *pdev = to_platform_device(dev);
>>   	struct at_dma *atdma = platform_get_drvdata(pdev);
>> +	struct dma_chan *chan, *_chan;
>>
>> -	at_dma_off(platform_get_drvdata(pdev));
>> +	/* preserve data */
>> +	list_for_each_entry_safe(chan, _chan,&atdma->dma_common.channels,
>> +			device_node) {
>> +		struct at_dma_chan *atchan = to_at_dma_chan(chan);
>> +
>> +		if (test_bit(ATC_IS_CYCLIC,&atchan->status))
>> +			atc_suspend_cyclic(atchan);
>> +		atchan->save_cfg = channel_readl(atchan, CFG);
>> +	}
>> +	atdma->save_imr = dma_readl(atdma, EBCIMR);
>> +
>> +	/* disable DMA controller */
>> +	at_dma_off(atdma);
>>   	clk_disable(atdma->clk);
>>   	return 0;
>>   }
>>
>> +static void atc_resume_cyclic(struct at_dma_chan *atchan)
>> +{
>> +	struct at_dma	*atdma = to_at_dma(atchan->chan_common.device);
>> +
>> +	/* restore channel status for cyclic descriptors list:
>> +	 * next descriptor in the cyclic list at the time of suspend */
>> +	channel_writel(atchan, SADDR, 0);
>> +	channel_writel(atchan, DADDR, 0);
>> +	channel_writel(atchan, CTRLA, 0);
>> +	channel_writel(atchan, CTRLB, 0);
>> +	channel_writel(atchan, DSCR, atchan->save_dscr);
>> +	dma_writel(atdma, CHER, atchan->mask);
>> +
>> +	/* channel pause status should be removed by channel user
>> +	 * We cannot take the initiative to do it here */
>> +
>> +	vdbg_dump_regs(atchan);
>> +}
>> +
>>   static int at_dma_resume_noirq(struct device *dev)
>>   {
>>   	struct platform_device *pdev = to_platform_device(dev);
>>   	struct at_dma *atdma = platform_get_drvdata(pdev);
>> +	struct dma_chan *chan, *_chan;
>>
>> +	/* bring back DMA controller */
>>   	clk_enable(atdma->clk);
>>   	dma_writel(atdma, EN, AT_DMA_ENABLE);
>> +
>> +	/* clear any pending interrupt */
>> +	while (dma_readl(atdma, EBCISR))
>> +		cpu_relax();
>> +
>> +	/* restore saved data */
>> +	dma_writel(atdma, EBCIER, atdma->save_imr);
>> +	list_for_each_entry_safe(chan, _chan,&atdma->dma_common.channels,
>> +			device_node) {
>> +		struct at_dma_chan *atchan = to_at_dma_chan(chan);
>> +
>> +		channel_writel(atchan, CFG, atchan->save_cfg);
>> +		if (test_bit(ATC_IS_CYCLIC,&atchan->status))
>> +			atc_resume_cyclic(atchan);
> This testing on bits seems to be reused few times how about wrapping it
> up in a routine?

True: I write a little patch for this and the "PAUSE" state. I send a 
patch for this now:
dmaengine: at_hdmac: add wrappers for testing channel state
So can you:
1/ queue 1/3 and 2/3 of this patch series
2/ queue the following patch named
"dmaengine: at_hdmac: add wrappers for testing channel state"
on top of that

3/ drop the patch 3/3 of this series: it certainly have to be reworked 
with all slave config infrastructure implementation in the at_hdmac driver.

>> +	}
>>   	return 0;
>>   }
>>
>>   static const struct dev_pm_ops at_dma_dev_pm_ops = {
>> +	.prepare = at_dma_prepare,
>>   	.suspend_noirq = at_dma_suspend_noirq,
>>   	.resume_noirq = at_dma_resume_noirq,
>>   };
>> diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h
>> index 087dbf1..6f0c4a3 100644
>> --- a/drivers/dma/at_hdmac_regs.h
>> +++ b/drivers/dma/at_hdmac_regs.h
>> @@ -204,6 +204,9 @@ enum atc_status {
>>    * @status: transmit status information from irq/prep* functions
>>    *                to tasklet (use atomic operations)
>>    * @tasklet: bottom half to finish transaction work
>> + * @save_cfg: configuration register that is saved on suspend/resume cycle
>> + * @save_dscr: for cyclic operations, preserve next descriptor address in
>> + *             the cyclic list on suspend/resume cycle
>>    * @lock: serializes enqueue/dequeue operations to descriptors lists
>>    * @completed_cookie: identifier for the most recently completed operation
>>    * @active_list: list of descriptors dmaengine is being running on
>> @@ -218,6 +221,8 @@ struct at_dma_chan {
>>   	u8			mask;
>>   	unsigned long		status;
>>   	struct tasklet_struct	tasklet;
>> +	u32			save_cfg;
>> +	u32			save_dscr;
>>
>>   	spinlock_t		lock;
>>
>> @@ -248,6 +253,7 @@ static inline struct at_dma_chan *to_at_dma_chan(struct dma_chan *dchan)
>>    * @chan_common: common dmaengine dma_device object members
>>    * @ch_regs: memory mapped register base
>>    * @clk: dma controller clock
>> + * @save_imr: interrupt mask register that is saved on suspend/resume cycle
>>    * @all_chan_mask: all channels availlable in a mask
>>    * @dma_desc_pool: base of DMA descriptor region (DMA address)
>>    * @chan: channels table to store at_dma_chan structures
>> @@ -256,6 +262,7 @@ struct at_dma {
>>   	struct dma_device	dma_common;
>>   	void __iomem		*regs;
>>   	struct clk		*clk;
>> +	u32			save_imr;
>>
>>   	u8			all_chan_mask;