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

[Koichiro Den]

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>
---
 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