Re: [PATCH 1/2] dmaengine: dw-edma: Add interrupt-emulation hooks

[Frank Li]

On Mon, Feb 16, 2026 at 12:22:15AM +0900, Koichiro Den wrote:
> DesignWare eDMA instances support "interrupt emulation", where a
> software write can assert the IRQ line without setting the normal
> DONE/ABORT status bits.
>
> Introduce core callbacks needed to support this feature:
>
>   - .ack_emulated_irq(): core-specific sequence to deassert an emulated
>     IRQ
>   - .db_offset(): offset from the DMA register base that is suitable as a
>     host-writable doorbell target for interrupt emulation
>
> Implement both hooks for the v0 register map. For dw-hdma-v0, provide a
> stub .db_offset() returning ~0 until the correct offset is known.
>
> The next patch wires these hooks into the dw-edma IRQ path and exports
> the doorbell resources to platform users.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
>  drivers/dma/dw-edma/dw-edma-core.h    | 17 +++++++++++++++++
>  drivers/dma/dw-edma/dw-edma-v0-core.c | 21 +++++++++++++++++++++
>  drivers/dma/dw-edma/dw-hdma-v0-core.c |  7 +++++++
>  3 files changed, 45 insertions(+)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
> index 71894b9e0b15..59b24973fa7d 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.h
> +++ b/drivers/dma/dw-edma/dw-edma-core.h
> @@ -126,6 +126,8 @@ struct dw_edma_core_ops {
>  	void (*start)(struct dw_edma_chunk *chunk, bool first);
>  	void (*ch_config)(struct dw_edma_chan *chan);
>  	void (*debugfs_on)(struct dw_edma *dw);
> +	void (*ack_emulated_irq)(struct dw_edma *dw);
> +	resource_size_t (*db_offset)(struct dw_edma *dw);
>  };
>
>  struct dw_edma_sg {
> @@ -206,4 +208,19 @@ void dw_edma_core_debugfs_on(struct dw_edma *dw)
>  	dw->core->debugfs_on(dw);
>  }
>
> +static inline int dw_edma_core_ack_emulated_irq(struct dw_edma *dw)
> +{
> +	if (!dw->core->ack_emulated_irq)
> +		return -EOPNOTSUPP;
> +
> +	dw->core->ack_emulated_irq(dw);
> +	return 0;
> +}
> +
> +static inline resource_size_t
> +dw_edma_core_db_offset(struct dw_edma *dw)
> +{
> +	return dw->core->db_offset(dw);
> +}
> +
>  #endif /* _DW_EDMA_CORE_H */
> diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> index b75fdaffad9a..69e8279adec8 100644
> --- a/drivers/dma/dw-edma/dw-edma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
> @@ -509,6 +509,25 @@ static void dw_edma_v0_core_debugfs_on(struct dw_edma *dw)
>  	dw_edma_v0_debugfs_on(dw);
>  }
>
> +static void dw_edma_v0_core_ack_emulated_irq(struct dw_edma *dw)
> +{
> +	/*
> +	 * Interrupt emulation may assert the IRQ without setting
> +	 * DONE/ABORT status bits. A zero write to INT_CLEAR deasserts the
> +	 * emulated IRQ, while being a no-op for real interrupts.
> +	 */
> +	SET_BOTH_32(dw, int_clear, 0);
> +}
> +
> +static resource_size_t dw_edma_v0_core_db_offset(struct dw_edma *dw)
> +{
> +	/*
> +	 * rd_int_status is chosen arbitrarily, but wr_int_status would be
> +	 * equally suitable.
> +	 */
> +	return offsetof(struct dw_edma_v0_regs, rd_int_status);
> +}
> +
>  static const struct dw_edma_core_ops dw_edma_v0_core = {
>  	.off = dw_edma_v0_core_off,
>  	.ch_count = dw_edma_v0_core_ch_count,
> @@ -517,6 +536,8 @@ static const struct dw_edma_core_ops dw_edma_v0_core = {
>  	.start = dw_edma_v0_core_start,
>  	.ch_config = dw_edma_v0_core_ch_config,
>  	.debugfs_on = dw_edma_v0_core_debugfs_on,
> +	.ack_emulated_irq = dw_edma_v0_core_ack_emulated_irq,
> +	.db_offset = dw_edma_v0_core_db_offset,
>  };
>
>  void dw_edma_v0_core_register(struct dw_edma *dw)
> diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> index e3f8db4fe909..1ae8e44f0a67 100644
> --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> @@ -283,6 +283,12 @@ static void dw_hdma_v0_core_debugfs_on(struct dw_edma *dw)
>  	dw_hdma_v0_debugfs_on(dw);
>  }
>
> +static resource_size_t dw_hdma_v0_core_db_offset(struct dw_edma *dw)
> +{
> +	/* Implement once the correct offset is known. */
> +	return ~0;
> +}
> +
>  static const struct dw_edma_core_ops dw_hdma_v0_core = {
>  	.off = dw_hdma_v0_core_off,
>  	.ch_count = dw_hdma_v0_core_ch_count,
> @@ -291,6 +297,7 @@ static const struct dw_edma_core_ops dw_hdma_v0_core = {
>  	.start = dw_hdma_v0_core_start,
>  	.ch_config = dw_hdma_v0_core_ch_config,
>  	.debugfs_on = dw_hdma_v0_core_debugfs_on,
> +	.db_offset = dw_hdma_v0_core_db_offset,
>  };
>
>  void dw_hdma_v0_core_register(struct dw_edma *dw)
> --
> 2.51.0
>