Re: [PATCH v6 10/18] dmaengine: sh: rz-dmac: Refactor pause/resume code

[Tommaso Merciai]

On Tue, May 26, 2026 at 11:47:02AM +0300, Claudiu Beznea wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
> 
> Subsequent patches will add suspend/resume and cyclic DMA support to the
> rz-dmac driver. This support needs to work on SoCs where power to most
> components (including DMA) is turned off during system suspend. For this,
> some channels (for example cyclic ones) may need to be paused and resumed
> manually by the DMA driver during system suspend/resume.
> 
> Refactor the pause/resume support so the same code can be reused in the
> system suspend/resume path.
>

Tested-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>

> Tested-by: John Madieu <john.madieu.xa@xxxxxxxxxxxxxx>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
> ---
> 
> Changes in v6:
> - collected tags
> 
> Changes in v5:
> - none
> 
> Changes in v4:
> - reset channel->status in rz_dmac_free_chan_resources() and
>   rz_dmac_terminate_all()
> 
> Changes in v3:
> - none, this patch new new
> 
>  drivers/dma/sh/rz-dmac.c | 73 ++++++++++++++++++++++++++++++++++------
>  1 file changed, 62 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
> index 1f884ec101f8..557364443a5f 100644
> --- a/drivers/dma/sh/rz-dmac.c
> +++ b/drivers/dma/sh/rz-dmac.c
> @@ -18,6 +18,7 @@
>  #include <linux/irqchip/irq-renesas-rzv2h.h>
>  #include <linux/irqchip/irq-renesas-rzt2h.h>
>  #include <linux/list.h>
> +#include <linux/lockdep.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_dma.h>
> @@ -63,6 +64,14 @@ struct rz_dmac_desc {
>  
>  #define to_rz_dmac_desc(d)	container_of(d, struct rz_dmac_desc, vd)
>  
> +/**
> + * enum rz_dmac_chan_status: RZ DMAC channel status
> + * @RZ_DMAC_CHAN_STATUS_PAUSED: Channel is paused though DMA engine callbacks
> + */
> +enum rz_dmac_chan_status {
> +	RZ_DMAC_CHAN_STATUS_PAUSED,
> +};
> +
>  struct rz_dmac_chan {
>  	struct virt_dma_chan vc;
>  	void __iomem *ch_base;
> @@ -74,6 +83,8 @@ struct rz_dmac_chan {
>  	dma_addr_t src_per_address;
>  	dma_addr_t dst_per_address;
>  
> +	unsigned long status;
> +
>  	u32 chcfg;
>  	u32 chctrl;
>  	int mid_rid;
> @@ -491,6 +502,8 @@ static void rz_dmac_free_chan_resources(struct dma_chan *chan)
>  		channel->mid_rid = -EINVAL;
>  	}
>  
> +	channel->status = 0;
> +
>  	spin_unlock_irqrestore(&channel->vc.lock, flags);
>  
>  	vchan_free_chan_resources(&channel->vc);
> @@ -589,6 +602,9 @@ static int rz_dmac_terminate_all(struct dma_chan *chan)
>  	}
>  
>  	vchan_get_all_descriptors(&channel->vc, &head);
> +
> +	channel->status = 0;
> +
>  	spin_unlock_irqrestore(&channel->vc.lock, flags);
>  	vchan_dma_desc_free_list(&channel->vc, &head);
>  
> @@ -795,35 +811,70 @@ static enum dma_status rz_dmac_tx_status(struct dma_chan *chan,
>  	return status;
>  }
>  
> -static int rz_dmac_device_pause(struct dma_chan *chan)
> +static int rz_dmac_device_pause_set(struct rz_dmac_chan *channel,
> +				    unsigned long set_bitmask)
>  {
> -	struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> +	int ret = 0;
>  	u32 val;
>  
> -	guard(spinlock_irqsave)(&channel->vc.lock);
> +	lockdep_assert_held(&channel->vc.lock);
>  
>  	if (!rz_dmac_chan_is_enabled(channel))
>  		return 0;
>  
> +	if (rz_dmac_chan_is_paused(channel))
> +		goto set_bit;
> +
>  	rz_dmac_ch_writel(channel, CHCTRL_SETSUS, CHCTRL, 1);
> -	return read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> -					(val & CHSTAT_SUS), 1, 1024,
> -					false, channel, CHSTAT, 1);
> +	ret = read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> +				       (val & CHSTAT_SUS), 1, 1024, false,
> +				       channel, CHSTAT, 1);
> +
> +set_bit:
> +	channel->status |= set_bitmask;
> +
> +	return ret;
>  }
>  
> -static int rz_dmac_device_resume(struct dma_chan *chan)
> +static int rz_dmac_device_pause(struct dma_chan *chan)
>  {
>  	struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> -	u32 val;
>  
>  	guard(spinlock_irqsave)(&channel->vc.lock);
>  
> +	return rz_dmac_device_pause_set(channel, BIT(RZ_DMAC_CHAN_STATUS_PAUSED));
> +}
> +
> +static int rz_dmac_device_resume_set(struct rz_dmac_chan *channel,
> +				     unsigned long clear_bitmask)
> +{
> +	int ret = 0;
> +	u32 val;
> +
> +	lockdep_assert_held(&channel->vc.lock);
> +
>  	/* Do not check CHSTAT_SUS but rely on HW capabilities. */
>  
>  	rz_dmac_ch_writel(channel, CHCTRL_CLRSUS, CHCTRL, 1);
> -	return read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> -					!(val & CHSTAT_SUS), 1, 1024,
> -					false, channel, CHSTAT, 1);
> +	ret = read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> +				       !(val & CHSTAT_SUS), 1, 1024, false,
> +				       channel, CHSTAT, 1);
> +
> +	channel->status &= ~clear_bitmask;
> +
> +	return ret;
> +}
> +
> +static int rz_dmac_device_resume(struct dma_chan *chan)
> +{
> +	struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> +
> +	guard(spinlock_irqsave)(&channel->vc.lock);
> +
> +	if (!(channel->status & BIT(RZ_DMAC_CHAN_STATUS_PAUSED)))
> +		return 0;
> +
> +	return rz_dmac_device_resume_set(channel, BIT(RZ_DMAC_CHAN_STATUS_PAUSED));
>  }
>  
>  /*
> -- 
> 2.43.0
>