Re: [PATCH RFC 2/8] dmaengine: Actions: Add support for S700 DMA engine

["André Przywara" <andre.przywara@arm.com>]

On 06/05/2020 11:36, Amit Singh Tomar wrote:

Hi,

> DMA controller present on S700 SoC is compatible with the one on S900
> (as most of registers are same), but it has different DMA descriptor
> structure where registers "fcnt" and "ctrlb" uses different encoding.
> 
> For instance, on S900 "fcnt" starts at offset 0x0c and uses upper 12
> bits whereas on S700, it starts at offset 0x1c and uses lower 12 bits.
> 
> This commit adds support for DMA controller present on S700.
> 
> Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
> ---
>  drivers/dma/owl-dma.c | 99 ++++++++++++++++++++++++++++++++++++---------------
>  1 file changed, 70 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/dma/owl-dma.c b/drivers/dma/owl-dma.c
> index b0d80a2fa383..6c2f0d0aad4c 100644
> --- a/drivers/dma/owl-dma.c
> +++ b/drivers/dma/owl-dma.c
> @@ -134,6 +134,11 @@ enum owl_dmadesc_offsets {
>  	OWL_DMADESC_SIZE
>  };
>  
> +enum owl_dma_id {
> +	S900_DMA,
> +	S700_DMA,
> +};
> +
>  /**
>   * struct owl_dma_lli - Link list for dma transfer
>   * @hw: hardware link list
> @@ -200,6 +205,7 @@ struct owl_dma_vchan {
>   * @pchans: array of data for the physical channels
>   * @nr_vchans: the number of physical channels
>   * @vchans: array of data for the physical channels
> + * @devid: device id based on OWL SoC
>   */
>  struct owl_dma {
>  	struct dma_device	dma;
> @@ -214,6 +220,7 @@ struct owl_dma {
>  
>  	unsigned int		nr_vchans;
>  	struct owl_dma_vchan	*vchans;
> +	enum owl_dma_id		devid;
>  };
>  
>  static void pchan_update(struct owl_dma_pchan *pchan, u32 reg,
> @@ -354,6 +361,7 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
>  				  struct dma_slave_config *sconfig,
>  				  bool is_cyclic)
>  {
> +	struct owl_dma *od = to_owl_dma(vchan->vc.chan.device);
>  	u32 mode, ctrlb;
>  
>  	mode = OWL_DMA_MODE_PW(0);
> @@ -409,8 +417,14 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
>  	lli->hw[OWL_DMADESC_DADDR] = dst;
>  	lli->hw[OWL_DMADESC_SRC_STRIDE] = 0;
>  	lli->hw[OWL_DMADESC_DST_STRIDE] = 0;
> -	lli->hw[OWL_DMADESC_FLEN] = len | 1 << 20;
> -	lli->hw[OWL_DMADESC_CTRLB] = ctrlb;
> +
> +	if (od->devid == S700_DMA) {
> +		lli->hw[OWL_DMADESC_FLEN] = len;
> +		lli->hw[OWL_DMADESC_CTRLB] = 1 | ctrlb;
> +	} else {
> +		lli->hw[OWL_DMADESC_FLEN] = len | 1 << 20;
> +		lli->hw[OWL_DMADESC_CTRLB] = ctrlb;
> +	}
>  
>  	return 0;
>  }
> @@ -562,26 +576,35 @@ static irqreturn_t owl_dma_interrupt(int irq, void *dev_id)
>  	dma_writel(od, OWL_DMA_IRQ_PD0, pending);
>  
>  	/* Check missed pending IRQ */
> -	for (i = 0; i < od->nr_pchans; i++) {
> -		pchan = &od->pchans[i];
> -		chan_irq_pending = pchan_readl(pchan, OWL_DMAX_INT_CTL) &
> -				   pchan_readl(pchan, OWL_DMAX_INT_STATUS);
> -
> -		/* Dummy read to ensure OWL_DMA_IRQ_PD0 value is updated */
> -		dma_readl(od, OWL_DMA_IRQ_PD0);
> +	if (od->devid == S900_DMA) {

You should mention (at least in the commit message) why this is needed.
And please move this into a separate function, this indentation is
becoming mad here.

> +		for (i = 0; i < od->nr_pchans; i++) {
> +			pchan = &od->pchans[i];
> +			chan_irq_pending = pchan_readl(pchan,
> +						       OWL_DMAX_INT_CTL) &
> +					   pchan_readl(pchan,
> +						       OWL_DMAX_INT_STATUS)
> +							;
> +
> +			/* Dummy read to ensure OWL_DMA_IRQ_PD0 value is
> +			 * updated
> +			 */
> +			dma_readl(od, OWL_DMA_IRQ_PD0);
>  
> -		global_irq_pending = dma_readl(od, OWL_DMA_IRQ_PD0);
> +			global_irq_pending = dma_readl(od,
> +						       OWL_DMA_IRQ_PD0);
>  
> -		if (chan_irq_pending && !(global_irq_pending & BIT(i)))	{
> -			dev_dbg(od->dma.dev,
> -				"global and channel IRQ pending match err\n");
> +			if (chan_irq_pending && !(global_irq_pending &
> +						  BIT(i))) {
> +				dev_dbg(od->dma.dev,
> +			"global and channel IRQ pending match err\n");
>  
> -			/* Clear IRQ status for this pchan */
> -			pchan_update(pchan, OWL_DMAX_INT_STATUS,
> -				     0xff, false);
> +				/* Clear IRQ status for this pchan */
> +				pchan_update(pchan, OWL_DMAX_INT_STATUS,
> +					     0xff, false);
>  
> -			/* Update global IRQ pending */
> -			pending |= BIT(i);
> +				/* Update global IRQ pending */
> +				pending |= BIT(i);
> +			}
>  		}
>  	}
>  
> @@ -720,6 +743,7 @@ static int owl_dma_resume(struct dma_chan *chan)
>  
>  static u32 owl_dma_getbytes_chan(struct owl_dma_vchan *vchan)
>  {
> +	struct owl_dma *od = to_owl_dma(vchan->vc.chan.device);
>  	struct owl_dma_pchan *pchan;
>  	struct owl_dma_txd *txd;
>  	struct owl_dma_lli *lli;
> @@ -741,9 +765,15 @@ static u32 owl_dma_getbytes_chan(struct owl_dma_vchan *vchan)
>  		list_for_each_entry(lli, &txd->lli_list, node) {
>  			/* Start from the next active node */
>  			if (lli->phys == next_lli_phy) {
> -				list_for_each_entry(lli, &txd->lli_list, node)
> -					bytes += lli->hw[OWL_DMADESC_FLEN] &
> -						 GENMASK(19, 0);
> +				list_for_each_entry(lli, &txd->lli_list, node) {
> +					if (od->devid == S700_DMA)
> +						bytes +=
> +						lli->hw[OWL_DMADESC_FLEN];
> +					else
> +						bytes +=
> +						lli->hw[OWL_DMADESC_FLEN] &
> +						GENMASK(19, 0);

You should have an accessor for getting the frame len, that should avoid
the insane wrapping here. Or factor this out into a helper function.
Alternatively revert the if statement and continue, that saves you one
level of indentation.

I guess flen is limited to 20 bits anyway, so you might want to apply
the 20-bit mask unconditionally.

Cheers,
Andre

> +				}
>  				break;
>  			}
>  		}
> @@ -756,6 +786,7 @@ static enum dma_status owl_dma_tx_status(struct dma_chan *chan,
>  					 dma_cookie_t cookie,
>  					 struct dma_tx_state *state)
>  {
> +	struct owl_dma *od = to_owl_dma(chan->device);
>  	struct owl_dma_vchan *vchan = to_owl_vchan(chan);
>  	struct owl_dma_lli *lli;
>  	struct virt_dma_desc *vd;
> @@ -773,8 +804,13 @@ static enum dma_status owl_dma_tx_status(struct dma_chan *chan,
>  	vd = vchan_find_desc(&vchan->vc, cookie);
>  	if (vd) {
>  		txd = to_owl_txd(&vd->tx);
> -		list_for_each_entry(lli, &txd->lli_list, node)
> -			bytes += lli->hw[OWL_DMADESC_FLEN] & GENMASK(19, 0);
> +		list_for_each_entry(lli, &txd->lli_list, node) {
> +			if (od->devid == S700_DMA)
> +				bytes += lli->hw[OWL_DMADESC_FLEN];
> +			else
> +				bytes += lli->hw[OWL_DMADESC_FLEN] &
> +					 GENMASK(19, 0);
> +		}
>  	} else {
>  		bytes = owl_dma_getbytes_chan(vchan);
>  	}
> @@ -1031,11 +1067,20 @@ static struct dma_chan *owl_dma_of_xlate(struct of_phandle_args *dma_spec,
>  	return chan;
>  }
>  
> +static const struct of_device_id owl_dma_match[] = {
> +	{ .compatible = "actions,s900-dma", .data = (void *)S900_DMA,},
> +	{ .compatible = "actions,s700-dma", .data = (void *)S700_DMA,},
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, owl_dma_match);
> +
>  static int owl_dma_probe(struct platform_device *pdev)
>  {
>  	struct device_node *np = pdev->dev.of_node;
>  	struct owl_dma *od;
>  	int ret, i, nr_channels, nr_requests;
> +	const struct of_device_id *of_id =
> +				of_match_device(owl_dma_match, &pdev->dev);
>  
>  	od = devm_kzalloc(&pdev->dev, sizeof(*od), GFP_KERNEL);
>  	if (!od)
> @@ -1060,6 +1105,8 @@ static int owl_dma_probe(struct platform_device *pdev)
>  	dev_info(&pdev->dev, "dma-channels %d, dma-requests %d\n",
>  		 nr_channels, nr_requests);
>  
> +	od->devid = (enum owl_dma_id)of_id->data;
> +
>  	od->nr_pchans = nr_channels;
>  	od->nr_vchans = nr_requests;
>  
> @@ -1192,12 +1239,6 @@ static int owl_dma_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -static const struct of_device_id owl_dma_match[] = {
> -	{ .compatible = "actions,s900-dma", },
> -	{ /* sentinel */ }
> -};
> -MODULE_DEVICE_TABLE(of, owl_dma_match);
> -
>  static struct platform_driver owl_dma_driver = {
>  	.probe	= owl_dma_probe,
>  	.remove	= owl_dma_remove,
>