[PATCH 02/12] dmaengine: dw-edma: Add channel lookup helper

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

Add a helper that maps a DesignWare eDMA write/read hardware channel
number to its DMAengine channel.

PCI endpoint resource enumeration uses the pointer only for later
ownership reservation.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/dma/dw-edma/dw-edma-core.c | 32 ++++++++++++++++++++++++++++++
 include/linux/dma/edma.h           |  8 ++++++++
 2 files changed, 40 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index c2feb3adc79f..6660380a1bbc 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -1189,6 +1189,38 @@ int dw_edma_remove(struct dw_edma_chip *chip)
 }
 EXPORT_SYMBOL_GPL(dw_edma_remove);
 
+struct dma_chan *dw_edma_find_channel(struct dw_edma_chip *chip, bool write,
+				      u16 id)
+{
+	struct dw_edma_chan *chan;
+	struct dw_edma *dw;
+
+	if (!chip)
+		return NULL;
+
+	dw = chip->dw;
+
+	if (!dw)
+		return NULL;
+
+	if (write) {
+		if (id >= dw->wr_ch_cnt)
+			return NULL;
+		chan = &dw->chan[id];
+		if (chan->dir != EDMA_DIR_WRITE)
+			return NULL;
+	} else {
+		if (id >= dw->rd_ch_cnt)
+			return NULL;
+		chan = &dw->chan[dw->wr_ch_cnt + id];
+		if (chan->dir != EDMA_DIR_READ)
+			return NULL;
+	}
+
+	return &chan->vc.chan;
+}
+EXPORT_SYMBOL_GPL(dw_edma_find_channel);
+
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("Synopsys DesignWare eDMA controller core driver");
 MODULE_AUTHOR("Gustavo Pimentel <gustavo.pimentel@synopsys.com>");
diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
index 1fafd5b0e315..b4b42b2278f3 100644
--- a/include/linux/dma/edma.h
+++ b/include/linux/dma/edma.h
@@ -110,6 +110,8 @@ struct dw_edma_chip {
 #if IS_REACHABLE(CONFIG_DW_EDMA)
 int dw_edma_probe(struct dw_edma_chip *chip);
 int dw_edma_remove(struct dw_edma_chip *chip);
+struct dma_chan *dw_edma_find_channel(struct dw_edma_chip *chip, bool write,
+				      u16 id);
 #else
 static inline int dw_edma_probe(struct dw_edma_chip *chip)
 {
@@ -120,6 +122,12 @@ static inline int dw_edma_remove(struct dw_edma_chip *chip)
 {
 	return 0;
 }
+
+static inline struct dma_chan *dw_edma_find_channel(struct dw_edma_chip *chip,
+						    bool write, u16 id)
+{
+	return NULL;
+}
 #endif /* CONFIG_DW_EDMA */
 
 #endif /* _DW_EDMA_H */
-- 
2.51.0