linux-kernel - RE: [PATCH v6 8/8] dmaengine: sh: rz-dmac: Add device

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Message-ID:
 <TY3PR01MB113466CA0EB792BF134502A7986B5A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Tue, 23 Dec 2025 14:43:44 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, "vkoul@...nel.org"
	<vkoul@...nel.org>, Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	"geert+renesas@...der.be" <geert+renesas@...der.be>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>
CC: Claudiu.Beznea <claudiu.beznea@...on.dev>, "dmaengine@...r.kernel.org"
	<dmaengine@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Claudiu Beznea
	<claudiu.beznea.uj@...renesas.com>
Subject: RE: [PATCH v6 8/8] dmaengine: sh: rz-dmac: Add
 device_{pause,resume}() callbacks

Hi Claudiu,

> -----Original Message-----
> From: Claudiu <claudiu.beznea@...on.dev>
> Sent: 23 December 2025 13:50
> Subject: [PATCH v6 8/8] dmaengine: sh: rz-dmac: Add device_{pause,resume}() callbacks
> 
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> 
> Add support for device_{pause, resume}() callbacks. These are required by the RZ/G2L SCIFA driver.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
> 
> Changes in v6:
> - set CHCTRL_SETSUS for pause and CHCTRL_CLRSUS for resume
> - dropped read-modify-update approach for CHCTRL updates as the
>   HW returns zero when reading CHCTRL
> - moved the read_poll_timeout_atomic() under spin lock to
>   ensure avoid any races b/w pause and resume functionalities
> 
> Changes in v5:
> - used suspend capability of the controller to pause/resume
>   the transfers
> 
>  drivers/dma/sh/rz-dmac.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c index 44f0f72cbcf1..377bdd5c9425
> 100644
> --- a/drivers/dma/sh/rz-dmac.c
> +++ b/drivers/dma/sh/rz-dmac.c
> @@ -135,10 +135,12 @@ struct rz_dmac {
>  #define CHANNEL_8_15_COMMON_BASE	0x0700
> 
>  #define CHSTAT_ER			BIT(4)
> +#define CHSTAT_SUS			BIT(3)
>  #define CHSTAT_EN			BIT(0)
> 
>  #define CHCTRL_CLRINTMSK		BIT(17)
>  #define CHCTRL_CLRSUS			BIT(9)
> +#define CHCTRL_SETSUS			BIT(8)
>  #define CHCTRL_CLRTC			BIT(6)
>  #define CHCTRL_CLREND			BIT(5)
>  #define CHCTRL_CLRRQ			BIT(4)
> @@ -827,6 +829,38 @@ static enum dma_status rz_dmac_tx_status(struct dma_chan *chan,
>  	return status;
>  }
> 
> +static int rz_dmac_device_pause(struct dma_chan *chan) {
> +	struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> +	u32 val;
> +	int ret;
> +
> +	scoped_guard(spinlock_irqsave, &channel->vc.lock) {

> +		rz_dmac_ch_writel(channel, CHCTRL_SETSUS, CHCTRL, 1);


Probably first you need to check CHSTAT_EN first before setting CHCTRL_SETSUS??

As per the hardware manual

"
Suspends the current DMA transfer. Setting this bit to 1 when 1 is set in EN of the
CHSTAT_n/nS register can suspend the current DMA transfer."


> +		ret = read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> +					       (val & CHSTAT_SUS), 1, 1024,
> +					       false, channel, CHSTAT, 1);
> +	}
> +
> +	return ret;
> +}
> +
> +static int rz_dmac_device_resume(struct dma_chan *chan) {
> +	struct rz_dmac_chan *channel = to_rz_dmac_chan(chan);
> +	u32 val;
> +	int ret;
> +
> +	scoped_guard(spinlock_irqsave, &channel->vc.lock) {


> +		rz_dmac_ch_writel(channel, CHCTRL_CLRSUS, CHCTRL, 1);


Similarly, first you need to check  CHSTAT_SUS bit first and then clear suspend state.


Clears the suspend status. Setting this bit to 1 when 1 is set in SUS of the
CHSTAT_n/nS register can clear the suspend status.

Cheers,
Biju


> +		ret = read_poll_timeout_atomic(rz_dmac_ch_readl, val,
> +					       !(val & CHSTAT_SUS), 1, 1024,
> +					       false, channel, CHSTAT, 1);
> +	}
> +
> +	return ret;
> +}
> +
>  /*
>   * -----------------------------------------------------------------------------
>   * IRQ handling
> @@ -1165,6 +1199,8 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  	engine->device_terminate_all = rz_dmac_terminate_all;
>  	engine->device_issue_pending = rz_dmac_issue_pending;
>  	engine->device_synchronize = rz_dmac_device_synchronize;
> +	engine->device_pause = rz_dmac_device_pause;
> +	engine->device_resume = rz_dmac_device_resume;
> 
>  	engine->copy_align = DMAENGINE_ALIGN_1_BYTE;
>  	dma_set_max_seg_size(engine->dev, U32_MAX);
> --
> 2.43.0