[PATCH] usb: renesas_usbhs: Revise the binding document about the dma-names

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Since the DT should describe the hardware (not the driver limitation),
This patch revises the binding document about the dma-names to change
simple numbering as "ch%d" instead of "tx<n>" and "rx<n>".

Also this patch fixes the actual code of renesas_usbhs driver to handle
the new dma-names.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
---
 This patch is based on Felipe's usb.bit / testing/next branch.
 (commit id = bbc78c07a51f6fd29c227b1220a9016e585358ba)

 Geert is pointed out about this issue:
 https://www.mail-archive.com/devicetree@vger.kernel.org/msg68401.html

 .../devicetree/bindings/usb/renesas_usbhs.txt      |  6 ++----
 drivers/usb/renesas_usbhs/fifo.c                   | 24 ++++++++++++++--------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/renesas_usbhs.txt b/Documentation/devicetree/bindings/usb/renesas_usbhs.txt
index dc2a18f..ddbe304 100644
--- a/Documentation/devicetree/bindings/usb/renesas_usbhs.txt
+++ b/Documentation/devicetree/bindings/usb/renesas_usbhs.txt
@@ -15,10 +15,8 @@ Optional properties:
   - phys: phandle + phy specifier pair
   - phy-names: must be "usb"
   - dmas: Must contain a list of references to DMA specifiers.
-  - dma-names : Must contain a list of DMA names:
-   - tx0 ... tx<n>
-   - rx0 ... rx<n>
-    - This <n> means DnFIFO in USBHS module.
+  - dma-names : named "ch%d", where %d is the channel number ranging from zero
+                to the number of channels (DnFIFOs) minus one.
 
 Example:
 	usbhs: usb@e6590000 {
diff --git a/drivers/usb/renesas_usbhs/fifo.c b/drivers/usb/renesas_usbhs/fifo.c
index 8597cf9..bc23b4a 100644
--- a/drivers/usb/renesas_usbhs/fifo.c
+++ b/drivers/usb/renesas_usbhs/fifo.c
@@ -1227,15 +1227,21 @@ static void usbhsf_dma_init_dt(struct device *dev, struct usbhs_fifo *fifo,
 {
 	char name[16];
 
-	snprintf(name, sizeof(name), "tx%d", channel);
-	fifo->tx_chan = dma_request_slave_channel_reason(dev, name);
-	if (IS_ERR(fifo->tx_chan))
-		fifo->tx_chan = NULL;
-
-	snprintf(name, sizeof(name), "rx%d", channel);
-	fifo->rx_chan = dma_request_slave_channel_reason(dev, name);
-	if (IS_ERR(fifo->rx_chan))
-		fifo->rx_chan = NULL;
+	/*
+	 * To avoid complex handing for DnFIFOs, the driver uses each
+	 * DnFIFO as TX or RX direction (not bi-direction).
+	 * So, the driver uses odd channels for TX, even channels for RX.
+	 */
+	snprintf(name, sizeof(name), "ch%d", channel);
+	if (channel & 1) {
+		fifo->tx_chan = dma_request_slave_channel_reason(dev, name);
+		if (IS_ERR(fifo->tx_chan))
+			fifo->tx_chan = NULL;
+	} else {
+		fifo->rx_chan = dma_request_slave_channel_reason(dev, name);
+		if (IS_ERR(fifo->rx_chan))
+			fifo->rx_chan = NULL;
+	}
 }
 
 static void usbhsf_dma_init(struct usbhs_priv *priv, struct usbhs_fifo *fifo,
-- 
1.9.1