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Commit fed2574b authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Vinod Koul
Browse files

dw_dmac: introduce software emulation of LLP transfers 



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: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarVinod Koul <vinod.koul@linux.intel.com>
parent a0982004

drivers/dma/dw_dmac.c

+95 −4
Original line number Diff line number Diff line
@@ -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);
@@ -558,9 +597,37 @@ 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);

		}

	}



	/*

	 * Re-enable interrupts.
@@ -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. */

drivers/dma/dw_dmac_regs.h

+6 −0
Original line number Diff line number Diff line
@@ -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;