[PATCH v4 02/14] dmaengine: dw-edma: Add per-channel interrupt routing control

[Koichiro Den <den@valinux.co.jp>]

DesignWare eDMA can signal completion locally through edma_int[] and
remotely through IMWr/MSI. When channels are delegated to a remote
frontend, the local endpoint side and the remote host side must not both
service the same DONE/ABORT status.

Add channel interrupt routing state and initialize it from the
controller instance configuration. Update the v0 eDMA and HDMA native
paths so linked-list interrupt generation, HDMA non-linked-list
interrupt enables, and DONE/ABORT masking follow the selected mode. For
HDMA native non-linked-list channels, use the dedicated remote
stop/abort enables without local stop/abort enables.

Keep the existing dw-edma-pcie host-side instances in remote interrupt
routing mode so their IMWr/MSI completion model remains unchanged after
local routing becomes the zero value.

Note:
- The routing mode describes where a channel should report completion.
  It does not by itself say whether this dw-edma instance owns the
  interrupt status. A local instance must ignore remote-only channels,
  and a remote instance must ignore local-only channels, even if such
  interrupts are unexpectedly delivered. Otherwise the non-owner side
  could steal the interrupt from the owner by clearing shared DONE/ABORT
  status.
- This drops the stop/abort interrupt masking that non-LL setup has
  applied since its introduction commit b7560798466a ("dmaengine:
  dw-edma: Add non-LL mode"). The databook's non-LL examples program the
  masks to zero in both directions, and with the local enables now
  cleared in remote mode there is no local interrupt left to mask.
  Remote-driven non-LL users keep the same delivered interrupts: the
  local pin was enabled-but-masked before and is not enabled at all now.

Cc: Devendra K Verma <devendra.verma@amd.com>
Suggested-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes in v4:
  - Document that a local instance never drives a remote-routed channel
    as the channel is handed over to and programmed by the remote side.
    (Sashiko)
  - Rename dw_edma_get_irq_mode() back to dw_edma_get_default_irq_mode()
    and simplify its implementation. (Frank)
  - Drop redundant dw_edma_get_irq_mode() call from
    dw_edma_alloc_chan_resources(). (Frank)
  - Drop unnecessary new-line drops. (Frank)
  - Simplify by just using DW_EDMA_CH_IRQ_REMOTE instead. (Frank)
  - Drop unnecessary chip->irq_mode. (Frank)
  - Revise int_setup for HDMA.

 drivers/dma/dw-edma/dw-edma-core.c    | 10 ++++++++
 drivers/dma/dw-edma/dw-edma-core.h    | 13 +++++++++++
 drivers/dma/dw-edma/dw-edma-v0-core.c | 28 +++++++++++++++++++----
 drivers/dma/dw-edma/dw-hdma-v0-core.c | 28 +++++++++++++++--------
 include/linux/dma/edma.h              | 33 +++++++++++++++++++++++++++
 5 files changed, 99 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 704d8f9746e8..1c6db2c381e2 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -255,6 +255,15 @@ static void dw_edma_device_caps(struct dma_chan *dchan,
 	}
 }
 
+static enum dw_edma_ch_irq_mode
+dw_edma_get_default_irq_mode(struct dw_edma_chan *chan)
+{
+	struct dw_edma_chip *chip = chan->dw->chip;
+
+	return chip->flags & DW_EDMA_CHIP_LOCAL ? DW_EDMA_CH_IRQ_LOCAL :
+						  DW_EDMA_CH_IRQ_REMOTE;
+}
+
 static int dw_edma_device_config(struct dma_chan *dchan,
 				 struct dma_slave_config *config)
 {
@@ -1016,6 +1025,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, u32 wr_alloc, u32 rd_alloc)
 		chan->configured = false;
 		chan->request = EDMA_REQ_NONE;
 		chan->status = EDMA_ST_IDLE;
+		chan->irq_mode = dw_edma_get_default_irq_mode(chan);
 		INIT_WORK(&chan->irq_work, dw_edma_irq_work);
 		atomic_set(&chan->irq_pending, 0);
 
diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
index a6a9ed09fe1b..3ea384706b1b 100644
--- a/drivers/dma/dw-edma/dw-edma-core.h
+++ b/drivers/dma/dw-edma/dw-edma-core.h
@@ -83,6 +83,8 @@ struct dw_edma_chan {
 
 	struct msi_msg			msi;
 
+	enum dw_edma_ch_irq_mode	irq_mode;
+
 	enum dw_edma_request		request;
 	enum dw_edma_status		status;
 	u8				configured;
@@ -236,4 +238,15 @@ dw_edma_core_db_offset(struct dw_edma *dw)
 	return dw->core->db_offset(dw);
 }
 
+static inline bool
+dw_edma_core_ch_ignore_irq(struct dw_edma_chan *chan)
+{
+	struct dw_edma *dw = chan->dw;
+
+	if (dw->chip->flags & DW_EDMA_CHIP_LOCAL)
+		return chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE;
+	else
+		return chan->irq_mode == DW_EDMA_CH_IRQ_LOCAL;
+}
+
 #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 377812eaa110..14700ac42fa8 100644
--- a/drivers/dma/dw-edma/dw-edma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
@@ -254,6 +254,9 @@ dw_edma_v0_core_handle_int(struct dw_edma_irq *dw_irq, enum dw_edma_dir dir,
 	for_each_set_bit(pos, &val, total) {
 		chan = &dw->chan[pos + off];
 
+		if (unlikely(dw_edma_core_ch_ignore_irq(chan)))
+			continue;
+
 		dw_edma_v0_core_clear_done_int(chan);
 		done(chan);
 
@@ -265,6 +268,9 @@ dw_edma_v0_core_handle_int(struct dw_edma_irq *dw_irq, enum dw_edma_dir dir,
 	for_each_set_bit(pos, &val, total) {
 		chan = &dw->chan[pos + off];
 
+		if (unlikely(dw_edma_core_ch_ignore_irq(chan)))
+			continue;
+
 		dw_edma_v0_core_clear_abort_int(chan);
 		abort(chan);
 
@@ -329,7 +335,16 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
 		j--;
 		if (!j) {
 			control |= DW_EDMA_V0_LIE;
-			if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
+
+			/*
+			 * A local instance never issues transfers on a
+			 * remote-routed channel: on CHIP_LOCAL instances,
+			 * REMOTE routing denotes a channel handed over to the
+			 * remote side, which programs the linked list through
+			 * its own instance.
+			 */
+			if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) &&
+			    chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE)
 				control |= DW_EDMA_V0_RIE;
 		}
 
@@ -406,12 +421,17 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 				break;
 			}
 		}
-		/* Interrupt unmask - done, abort */
+		/* Interrupt mask/unmask - done, abort */
 		raw_spin_lock_irqsave(&dw->lock, flags);
 
 		tmp = GET_RW_32(dw, chan->dir, int_mask);
-		tmp &= ~FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
-		tmp &= ~FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
+		if (chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE) {
+			tmp |= FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
+			tmp |= FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
+		} else {
+			tmp &= ~FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
+			tmp &= ~FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
+		}
 		SET_RW_32(dw, chan->dir, int_mask, tmp);
 		/* Linked list error */
 		tmp = GET_RW_32(dw, chan->dir, linked_list_err_en);
diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
index 44e7b6c1263c..cc908ca24061 100644
--- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
@@ -52,17 +52,25 @@ __dw_ch_regs(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch)
 /* HDMA management callbacks */
 static u32 dw_hdma_v0_core_int_setup(struct dw_edma_chan *chan, u32 val)
 {
-	if (chan->non_ll)
-		val |= HDMA_V0_STOP_INT_MASK | HDMA_V0_ABORT_INT_MASK;
-	else
-		val &= ~(HDMA_V0_STOP_INT_MASK | HDMA_V0_ABORT_INT_MASK);
+	val &= ~(HDMA_V0_LOCAL_ABORT_INT_EN | HDMA_V0_REMOTE_ABORT_INT_EN |
+		 HDMA_V0_LOCAL_STOP_INT_EN | HDMA_V0_REMOTE_STOP_INT_EN |
+		 HDMA_V0_ABORT_INT_MASK | HDMA_V0_STOP_INT_MASK);
 
-	val |= HDMA_V0_LOCAL_STOP_INT_EN | HDMA_V0_LOCAL_ABORT_INT_EN;
-	if (!(chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
-		val |= HDMA_V0_REMOTE_STOP_INT_EN |
-		       HDMA_V0_REMOTE_ABORT_INT_EN;
+	/*
+	 * DWC PCIe DM Databook 6.10a-lca06 remote non-LL examples
+	 * program LSIE/LAIE=0 and RSIE/RAIE=1. Use the HDMA remote
+	 * enable bits directly for stop/abort routing.
+	 *
+	 * This is unlike the eDMA LIE/RIE and HDMA LL LWIE/RWIE paths:
+	 * those pair local and remote enables and mask the local interrupt
+	 * path, but HDMA stop/abort has separate remote enable bits.
+	 */
+	if (chan->irq_mode == DW_EDMA_CH_IRQ_REMOTE)
+		return val | HDMA_V0_REMOTE_ABORT_INT_EN |
+			     HDMA_V0_REMOTE_STOP_INT_EN;
 
-	return val;
+	return val | HDMA_V0_LOCAL_ABORT_INT_EN |
+		     HDMA_V0_LOCAL_STOP_INT_EN;
 }
 
 static void dw_hdma_v0_core_off(struct dw_edma *dw)
@@ -147,6 +155,8 @@ dw_hdma_v0_core_handle_int(struct dw_edma_irq *dw_irq, enum dw_edma_dir dir,
 
 	for_each_set_bit(pos, &mask, total) {
 		chan = &dw->chan[pos + off];
+		if (unlikely(dw_edma_core_ch_ignore_irq(chan)))
+			continue;
 
 		val = dw_hdma_v0_core_status_int(chan);
 		if (FIELD_GET(HDMA_V0_STOP_INT_MASK, val)) {
diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
index 1fafd5b0e315..1007122d4123 100644
--- a/include/linux/dma/edma.h
+++ b/include/linux/dma/edma.h
@@ -60,6 +60,39 @@ enum dw_edma_chip_flags {
 	DW_EDMA_CHIP_LOCAL	= BIT(0),
 };
 
+/**
+ * enum dw_edma_ch_irq_mode - per-channel interrupt routing control
+ * @DW_EDMA_CH_IRQ_LOCAL:     local interrupt only (edma_int[])
+ * @DW_EDMA_CH_IRQ_REMOTE:    remote interrupt only (IMWr/MSI), without
+ *                            delivering local edma_int[].
+ *
+ * DesignWare EP eDMA can signal interrupts locally through the edma_int[]
+ * bus, and remotely using posted memory writes (IMWr) that may be
+ * interpreted as MSI/MSI-X by the RC.
+ *
+ * For the v0 eDMA linked-list programming path, DMA_*_INT_MASK gates the local
+ * edma_int[] assertion, while there is no dedicated per-channel mask for IMWr
+ * generation. To request a remote-only interrupt, Synopsys recommends setting
+ * both LIE and RIE, and masking the local interrupt in DMA_*_INT_MASK. See the
+ * DesignWare endpoint databook 6.30a, Linked List Mode interrupt handling
+ * ("Software Programming of an Endpoint's LIE and RIE Bits for Linked List
+ * Transfers", Attention).
+ *
+ * A local (DW_EDMA_CHIP_LOCAL) instance never issues transfers on a
+ * remote-routed channel: REMOTE routing on such an instance denotes a channel
+ * handed over to and driven by the remote side, and the recipe above is
+ * applied by the driving instance.
+ *
+ * HDMA linked-list watermark interrupts have the same LWIE/RWIE guidance. HDMA
+ * non-linked-list mode has dedicated local and remote stop/abort interrupt
+ * enables, and the remote CPU programming examples use remote enables without
+ * local enables.
+ */
+enum dw_edma_ch_irq_mode {
+	DW_EDMA_CH_IRQ_LOCAL	= 0,
+	DW_EDMA_CH_IRQ_REMOTE,
+};
+
 /**
  * struct dw_edma_chip - representation of DesignWare eDMA controller hardware
  * @dev:		 struct device of the eDMA controller
-- 
2.51.0