linux-kernel - [RFC PATCH 17/25] dmaengine: dw-edma: Add dw_edma_find_by

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Message-ID: <20251023071916.901355-18-den@valinux.co.jp>
Date: Thu, 23 Oct 2025 16:19:08 +0900
From: Koichiro Den <den@...inux.co.jp>
To: ntb@...ts.linux.dev,
	linux-pci@...r.kernel.org,
	dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
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Subject: [RFC PATCH 17/25] dmaengine: dw-edma: Add dw_edma_find_by_child() helper

Add a helper to locate a dw_edma instance by its child device pointer.
Used by PCI endpoint functions to locate the shared eDMA controller.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 drivers/dma/dw-edma/dw-edma-core.c | 26 ++++++++++++++++++++++++++
 drivers/dma/dw-edma/dw-edma-core.h |  2 ++
 include/linux/dma/edma.h           |  5 +++++
 3 files changed, 33 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 28cc319e224d..6c7495504456 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -24,6 +24,9 @@
 #include "../dmaengine.h"
 #include "../virt-dma.h"
 
+static DEFINE_MUTEX(dw_edma_list_lock);
+static LIST_HEAD(dw_edma_list);
+
 static inline
 struct dw_edma_desc *vd2dw_edma_desc(struct virt_dma_desc *vd)
 {
@@ -964,6 +967,22 @@ void dw_edma_unregister_selfirq(struct dw_edma *dw,
 }
 EXPORT_SYMBOL_GPL(dw_edma_unregister_selfirq);
 
+struct dw_edma *dw_edma_find_by_child(struct device *child)
+{
+	struct dw_edma *dw;
+
+	if (!child)
+		return NULL;
+
+	guard(mutex)(&dw_edma_list_lock);
+	list_for_each_entry(dw, &dw_edma_list, node)
+		if (child->parent == dw->dma.dev)
+			return dw;
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(dw_edma_find_by_child);
+
 int dw_edma_probe(struct dw_edma_chip *chip)
 {
 	struct device *dev;
@@ -1035,6 +1054,10 @@ int dw_edma_probe(struct dw_edma_chip *chip)
 
 	chip->dw = dw;
 
+	INIT_LIST_HEAD(&dw->node);
+	guard(mutex)(&dw_edma_list_lock);
+	list_add_tail(&dw->node, &dw_edma_list);
+
 	return 0;
 
 err_irq_free:
@@ -1080,6 +1103,9 @@ int dw_edma_remove(struct dw_edma_chip *chip)
 		list_del(&chan->vc.chan.device_node);
 	}
 
+	guard(mutex)(&dw_edma_list_lock);
+	list_del(&dw->node);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(dw_edma_remove);
diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
index 7d7dd9f13863..249d7e153cbf 100644
--- a/drivers/dma/dw-edma/dw-edma-core.h
+++ b/drivers/dma/dw-edma/dw-edma-core.h
@@ -122,6 +122,8 @@ struct dw_edma {
 
 	struct list_head selfirq_handlers;
 	spinlock_t selfirq_lock;
+
+	struct list_head		node;
 };
 
 typedef void (*dw_edma_handler_t)(struct dw_edma_chan *);
diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
index 1f11b70e1b1a..abc59ffde62c 100644
--- a/include/linux/dma/edma.h
+++ b/include/linux/dma/edma.h
@@ -115,6 +115,7 @@ int dw_edma_register_selfirq(struct dw_edma *dw,
 			     dw_edma_selfirq_fn fn, void *data);
 void dw_edma_unregister_selfirq(struct dw_edma *dw,
 				dw_edma_selfirq_fn fn, void *data);
+struct dw_edma *dw_edma_find_by_child(struct device *child);
 #else
 static inline int dw_edma_probe(struct dw_edma_chip *chip)
 {
@@ -141,6 +142,10 @@ static inline void dw_edma_unregister_selfirq(struct dw_edma *dw,
 					      dw_edma_selfirq_fn fn, void *data)
 {
 }
+struct dw_edma *dw_edma_find_by_child(struct device *child)
+{
+	return NULL;
+}
 #endif /* CONFIG_DW_EDMA */
 
 #endif /* _DW_EDMA_H */
-- 
2.48.1