Re: [PATCH v5 3/5] dmaengine: sun6i-dma: Add num_channels_per_reg for flexible interrupt mapping

[Frank Li]

On Wed, Aug 26, 2026 at 02:40:29AM +0000, Yuanshen Cao wrote:
> The `sun6i-dma` driver previously assumed a fixed number of channels
> per interrupt register. For example, `sun6i_kill_tasklet` was hardcoded
> to disable interrupts only for registers 0 and 1. `DMA_MAX_CHANNELS` was
> also not in used previously, and the old SoCs never has more than 16
> channels.
>
> The A733 has a different interrupt structure where the number of
> channels per register may differ. Add `num_channels_per_reg` to `struct
> sun6i_dma_config` to make the interrupt handling logic handware-agnostic
> Update `sun6i_dma_interrupt`, `sun6i_dma_start_desc`, and
> `sun6i_kill_tasklet` to use this value.
>
> Additionally, set `DMA_MAX_CHANNELS` to 16 to ensure loops over
> interrupts are correctly bounded, aligning with the hardware
> specifications.
>
> Signed-off-by: Yuanshen Cao <alex.caoys@xxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/sun6i-dma.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index 1ffd870d9594..ffb63212bea7 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -32,14 +32,13 @@
>  #define DMA_IRQ_PKG			BIT(1)
>  #define DMA_IRQ_QUEUE			BIT(2)
>
> -#define DMA_IRQ_CHAN_NR			8
>  #define DMA_IRQ_CHAN_WIDTH		4
>
>
>  #define DMA_STAT		0x30
>
>  /* Offset between DMA_IRQ_EN and DMA_IRQ_STAT limits number of channels */
> -#define DMA_MAX_CHANNELS	(DMA_IRQ_CHAN_NR * 0x10 / 4)
> +#define DMA_MAX_CHANNELS	16
>
>  /*
>   * sun8i specific registers
> @@ -58,6 +57,8 @@
>  #define DMA_IRQ_EN_OFFSET_A31		0x00
>  #define DMA_IRQ_STAT_OFFSET_A31		0x10
>
> +#define DMA_IRQ_CHAN_NR_A31		8
> +
>  /*
>   * Channels specific registers
>   */
> @@ -154,6 +155,7 @@ struct sun6i_dma_config {
>  	u32 irq_stride;
>  	u32 irq_en_offset;
>  	u32 irq_stat_offset;
> +	u32 num_channels_per_reg;
>  };
>
>  /*
> @@ -268,7 +270,7 @@ static inline void sun6i_dma_dump_com_regs(struct sun6i_dma_dev *sdev)
>  {
>  	int i;
>
> -	for (i = 0; i < 2; i++) {
> +	for (i = 0; i < DIV_ROUND_UP(sdev->num_pchans, sdev->cfg->num_channels_per_reg); i++) {
>  		dev_dbg(sdev->slave.dev, "Common register:\n"
>  			"chan num %d\n"
>  			"\tmask(%04x): 0x%08x\n"
> @@ -489,8 +491,8 @@ static int sun6i_dma_start_desc(struct sun6i_vchan *vchan)
>
>  	sun6i_dma_dump_lli(vchan, pchan->desc->v_lli, pchan->desc->p_lli);
>
> -	irq_reg = pchan->idx / DMA_IRQ_CHAN_NR;
> -	irq_offset = pchan->idx % DMA_IRQ_CHAN_NR;
> +	irq_reg = pchan->idx / sdev->cfg->num_channels_per_reg;
> +	irq_offset = pchan->idx % sdev->cfg->num_channels_per_reg;
>
>  	vchan->irq_type = vchan->cyclic ? DMA_IRQ_PKG : DMA_IRQ_QUEUE;
>
> @@ -582,7 +584,7 @@ static irqreturn_t sun6i_dma_interrupt(int irq, void *dev_id)
>  	int i, j, ret = IRQ_NONE;
>  	u32 status;
>
> -	for (i = 0; i < sdev->num_pchans / DMA_IRQ_CHAN_NR; i++) {
> +	for (i = 0; i < sdev->num_pchans / sdev->cfg->num_channels_per_reg; i++) {
>  		status = sun6i_read_irq_stat(sdev, i);
>  		if (!status)
>  			continue;
> @@ -592,7 +594,7 @@ static irqreturn_t sun6i_dma_interrupt(int irq, void *dev_id)
>
>  		sun6i_write_irq_stat(sdev, i, status);
>
> -		for (j = 0; (j < DMA_IRQ_CHAN_NR) && status; j++) {
> +		for (j = 0; (j < sdev->cfg->num_channels_per_reg) && status; j++) {
>  			pchan = sdev->pchans + j;
>  			vchan = pchan->vchan;
>  			if (vchan && (status & vchan->irq_type)) {
> @@ -1110,7 +1112,7 @@ static inline void sun6i_kill_tasklet(struct sun6i_dma_dev *sdev)
>  	int i;
>
>  	/* Disable all interrupts from DMA */
> -	for (i = 0; i < 2; i++)
> +	for (i = 0; i < DMA_MAX_CHANNELS / sdev->cfg->num_channels_per_reg; i++)
>  		sun6i_write_irq_en(sdev, i, 0);
>
>  	/* Prevent spurious interrupts from scheduling the tasklet */
> @@ -1138,7 +1140,8 @@ static inline void sun6i_dma_free(struct sun6i_dma_dev *sdev)
>  #define SUN6I_DMA_IRQ_A31_COMMON_CFG	\
>  	.irq_stride      = DMA_IRQ_STRIDE_A31,	\
>  	.irq_en_offset   = DMA_IRQ_EN_OFFSET_A31,	\
> -	.irq_stat_offset = DMA_IRQ_STAT_OFFSET_A31,
> +	.irq_stat_offset = DMA_IRQ_STAT_OFFSET_A31,	\
> +	.num_channels_per_reg = DMA_IRQ_CHAN_NR_A31,
>
>  /*
>   * For A31:
>
> --
> 2.55.0
>