Re: [PATCH 7/7] dw_dmac: introduce software emulation of LLP transfers

viresh kumar
2012-09-18T07:17:55Z

On Mon, Sep 17, 2012 at 1:09 PM, Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
> index 00958ad..fa23711 100644
> --- a/drivers/dma/dw_dmac.c
> +++ b/drivers/dma/dw_dmac.c
> @@ -229,10 +229,29 @@ 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) {
> @@ -244,6 +263,26 @@ 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);
> @@ -555,8 +594,36 @@ 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);

can come in single line.

> +
> + 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);
> + }
> }
>
> /*
> @@ -647,12 +714,6 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
> unsigned int dst_width;
> u32 ctllo;
>
> - if (dwc->nollp) {
> - dev_dbg(chan2dev(&dwc->chan),
> - "channel doesn't support LLP transfers\n");
> - return NULL;
> - }
> -

:)
You should actually merge 6/7 with 7/7... You can't revert something
in the same patchset.

viresh