Re: [PATCH 2/5] dmaengine: at_hdmac: add cyclic DMA operation support

[Nicolas Ferre]

Le 06/04/2011 12:08, Koul, Vinod :
> On Fri, 2011-04-01 at 19:19 +0200, Nicolas Ferre wrote:
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
>> ---
>>  drivers/dma/at_hdmac.c      |  188 +++++++++++++++++++++++++++++++++++++++---
>>  drivers/dma/at_hdmac_regs.h |   14 +++-
>>  2 files changed, 186 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
>> index 13050e6..fe9e1de 100644
>> --- a/drivers/dma/at_hdmac.c
>> +++ b/drivers/dma/at_hdmac.c
>> @@ -14,6 +14,8 @@
>>   * The driver has currently been tested with the Atmel AT91SAM9RL
>>   * and AT91SAM9G45 series.
>>   */
>> +#define DEBUG 12
>> +#define VERBOSE_DEBUG 12
> Please don't define here and use debug options available for build

Yes, sure sorry.

>> +/**
>> + * atc_handle_cyclic - at the end of a period, run callback function
>> + * @atchan: channel used for cyclic operations
>> + *
>> + * Called with atchan->lock held and bh disabled
>> + */
>> +static void atc_handle_cyclic(struct at_dma_chan *atchan)
>> +{
>> +	struct at_desc			*first = atc_first_active(atchan);
>> +	struct dma_async_tx_descriptor	*txd = &first->txd;
>> +	dma_async_tx_callback		callback = txd->callback;
>> +	void				*param = txd->callback_param;
>> +
>> +	dev_vdbg(chan2dev(&atchan->chan_common),
>> +			"new cyclic period llp 0x%08x\n",
>> +			channel_readl(atchan, DSCR));
>> +
>> +	if (callback)
>> +		callback(param);
>> +}
> You dont seem to be doing much expect calling callback, so doesn't it
> make sense to write so much code for just calling callback? 

I do not totally follow you here: you mean that I should reduce the
amount of variables in this function or is it a more global comment
about my way of handling cyclic operations?

>>  
>>  /*--  IRQ & Tasklet  ---------------------------------------------------*/
>>  
>> @@ -434,8 +459,10 @@ static void atc_tasklet(unsigned long data)
>>  	}
>>  
>>  	spin_lock(&atchan->lock);
>> -	if (test_and_clear_bit(0, &atchan->error_status))
>> +	if (test_and_clear_bit(ATC_IS_ERROR, &atchan->status))
>>  		atc_handle_error(atchan);
>> +	else if (test_bit(ATC_IS_CYCLIC, &atchan->status))
>> +		atc_handle_cyclic(atchan);
>>  	else
>>  		atc_advance_work(atchan);
>>  
>> @@ -469,7 +496,7 @@ static irqreturn_t at_dma_interrupt(int irq, void *dev_id)
>>  					/* Disable channel on AHB error */
>>  					dma_writel(atdma, CHDR, atchan->mask);
>>  					/* Give information to tasklet */
>> -					set_bit(0, &atchan->error_status);
>> +					set_bit(ATC_IS_ERROR, &atchan->status);
>>  				}
>>  				tasklet_schedule(&atchan->tasklet);
>>  				ret = IRQ_HANDLED;
>> @@ -759,6 +786,127 @@ err_desc_get:
>>  	return NULL;
>>  }
>>  
>> +/**
>> + * atc_dma_cyclic_prep - prepare the cyclic DMA transfer
>> + * @chan: the DMA channel to prepare
>> + * @buf_addr: physical DMA address where the buffer starts
>> + * @buf_len: total number of bytes for the entire buffer
>> + * @period_len: number of bytes for each period
>> + * @direction: transfer direction, to or from device
>> + */
>> +static struct dma_async_tx_descriptor *
>> +atc_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
>> +		size_t period_len, enum dma_data_direction direction)
>> +{
>> +	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
>> +	struct at_dma_slave	*atslave = chan->private;
>> +	struct at_desc		*first = NULL;
>> +	struct at_desc		*prev = NULL;
>> +	unsigned long		was_cyclic;
>> +	unsigned int		periods = buf_len / period_len;
>> +	unsigned int		reg_width;
>> +	u32			ctrla;
>> +	u32			ctrlb;
>> +	unsigned int		i;
>> +
>> +	dev_vdbg(chan2dev(chan), "prep_dma_cyclic: %s buf@0x%08x - %d (%d/%d)\n",
>> +			direction == DMA_TO_DEVICE ? "TO DEVICE" : "FROM DEVICE",
>> +			buf_addr,
>> +			periods, buf_len, period_len);
>> +
>> +	if (unlikely(!atslave || !buf_len || !period_len)) {
>> +		dev_dbg(chan2dev(chan), "prep_dma_cyclic: length is zero!\n");
>> +		return NULL;
>> +	}
>> +
>> +	was_cyclic = test_and_set_bit(ATC_IS_CYCLIC, &atchan->status);
>> +	if (was_cyclic) {
>> +		dev_dbg(chan2dev(chan), "prep_dma_cyclic: channel in use!\n");
>> +		return NULL;
>> +	}
>> +
>> +	reg_width = atslave->reg_width;
>> +
>> +	/* Check for too big/unaligned periods and unaligned DMA buffer */
>> +	if (period_len > (ATC_BTSIZE_MAX << reg_width))
>> +		goto err_out;
>> +	if (unlikely(period_len & ((1 << reg_width) - 1)))
>> +		goto err_out;
>> +	if (unlikely(buf_addr & ((1 << reg_width) - 1)))
>> +		goto err_out;
>> +	if (unlikely(!(direction & (DMA_TO_DEVICE | DMA_FROM_DEVICE))))
>> +		goto err_out;
>> +
>> +	/* prepare common CRTLA/CTRLB values */
>> +	ctrla =   ATC_DEFAULT_CTRLA | atslave->ctrla
>> +		| ATC_DST_WIDTH(reg_width)
>> +		| ATC_SRC_WIDTH(reg_width)
>> +		| period_len >> reg_width;
>> +	ctrlb = ATC_DEFAULT_CTRLB;
>> +
>> +	/* build cyclic linked list */
>> +	for (i = 0; i < periods; i++) {
> would help making code look cleaner if you split this one to seprate
> function

Ok, I will see what I can do... and will post a v2 soon.

>> +		struct at_desc	*desc;
>> +
>> +		desc = atc_desc_get(atchan);
>> +		if (!desc)
>> +			goto err_desc_get;
>> +
>> +		switch (direction) {
>> +		case DMA_TO_DEVICE:
>> +			desc->lli.saddr = buf_addr + (period_len * i);
>> +			desc->lli.daddr = atslave->tx_reg;
>> +			desc->lli.ctrla = ctrla;
>> +			desc->lli.ctrlb = ctrlb
>> +					| ATC_DST_ADDR_MODE_FIXED
>> +					| ATC_SRC_ADDR_MODE_INCR
>> +					| ATC_FC_MEM2PER;
>> +			break;
>> +
>> +		case DMA_FROM_DEVICE:
>> +			desc->lli.saddr = atslave->rx_reg;
>> +			desc->lli.daddr = buf_addr + (period_len * i);
>> +			desc->lli.ctrla = ctrla;
>> +			desc->lli.ctrlb = ctrlb
>> +					| ATC_DST_ADDR_MODE_INCR
>> +					| ATC_SRC_ADDR_MODE_FIXED
>> +					| ATC_FC_PER2MEM;
>> +			break;
>> +
>> +		default:
>> +			return NULL;
>> +		}
>> +
>> +		if (!first) {
>> +			first = desc;
>> +		} else {
>> +			/* inform the HW lli about chaining */
>> +			prev->lli.dscr = desc->txd.phys;
>> +			/* insert the link descriptor to the LD ring */
>> +			list_add_tail(&desc->desc_node,
>> +					&first->tx_list);
>> +		}
>> +		prev = desc;
>> +	}
>> +
>> +	/* lets make a cyclic list */
>> +	prev->lli.dscr = first->txd.phys;
>> +
>> +	/* First descriptor of the chain embedds additional information */
>> +	first->txd.cookie = -EBUSY;
>> +	first->len = buf_len;
>> +
>> +	return &first->txd;
>> +
>> +err_desc_get:
>> +	dev_err(chan2dev(chan), "not enough descriptors available\n");
>> +	atc_desc_put(atchan, first);
>> +err_out:
>> +	clear_bit(ATC_IS_CYCLIC, &atchan->status);
>> +	return NULL;
>> +}
>> +
>> +
>>  static int atc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
>>  		       unsigned long arg)
>>  {
>> @@ -793,6 +941,9 @@ static int atc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
>>  	list_for_each_entry_safe(desc, _desc, &list, desc_node)
>>  		atc_chain_complete(atchan, desc);
>>  
>> +	/* if channel dedicated to cyclic operations, free it */
>> +	clear_bit(ATC_IS_CYCLIC, &atchan->status);
>> +
>>  	spin_unlock_bh(&atchan->lock);
>>  
>>  	return 0;
>> @@ -853,6 +1004,10 @@ static void atc_issue_pending(struct dma_chan *chan)
>>  
>>  	dev_vdbg(chan2dev(chan), "issue_pending\n");
>>  
>> +	/* Not needed for cyclic transfers */
>> +	if (test_bit(ATC_IS_CYCLIC, &atchan->status))
>> +		return;
>> +
>>  	spin_lock_bh(&atchan->lock);
>>  	if (!atc_chan_is_enabled(atchan)) {
>>  		atc_advance_work(atchan);
>> @@ -1092,10 +1247,15 @@ static int __init at_dma_probe(struct platform_device *pdev)
>>  	if (dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask))
>>  		atdma->dma_common.device_prep_dma_memcpy = atc_prep_dma_memcpy;
>>  
>> -	if (dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask)) {
>> +	if (dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask))
>>  		atdma->dma_common.device_prep_slave_sg = atc_prep_slave_sg;
>> +
>> +	if (dma_has_cap(DMA_CYCLIC, atdma->dma_common.cap_mask))
>> +		atdma->dma_common.device_prep_dma_cyclic = atc_prep_dma_cyclic;
>> +
>> +	if (dma_has_cap(DMA_SLAVE, atdma->dma_common.cap_mask) ||
>> +	    dma_has_cap(DMA_CYCLIC, atdma->dma_common.cap_mask))
>>  		atdma->dma_common.device_control = atc_control;
>> -	}
>>  
>>  	dma_writel(atdma, EN, AT_DMA_ENABLE);
>>  
>> diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h
>> index 8303306..c79a9e0 100644
>> --- a/drivers/dma/at_hdmac_regs.h
>> +++ b/drivers/dma/at_hdmac_regs.h
>> @@ -181,12 +181,22 @@ txd_to_at_desc(struct dma_async_tx_descriptor *txd)
>>  /*--  Channels  --------------------------------------------------------*/
>>  
>>  /**
>> + * atc_status - information bits stored in channel status flag
>> + *
>> + * Manipulated with atomic operations.
>> + */
>> +enum atc_status {
>> +	ATC_IS_ERROR = 0,
>> +	ATC_IS_CYCLIC = 24,
>> +};
>> +
>> +/**
>>   * struct at_dma_chan - internal representation of an Atmel HDMAC channel
>>   * @chan_common: common dmaengine channel object members
>>   * @device: parent device
>>   * @ch_regs: memory mapped register base
>>   * @mask: channel index in a mask
>> - * @error_status: transmit error status information from irq handler
>> + * @status: transmit status information from irq/prep* functions
>>   *                to tasklet (use atomic operations)
>>   * @tasklet: bottom half to finish transaction work
>>   * @lock: serializes enqueue/dequeue operations to descriptors lists
>> @@ -201,7 +211,7 @@ struct at_dma_chan {
>>  	struct at_dma		*device;
>>  	void __iomem		*ch_regs;
>>  	u8			mask;
>> -	unsigned long		error_status;
>> +	unsigned long		status;
>>  	struct tasklet_struct	tasklet;
>>  
>>  	spinlock_t		lock;


Thanks for your review, best regards,
-- 
Nicolas Ferre

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