usb: renesas_usbhs: add DMAEngine ID specification note

renesas_usbhs DMAEngine uses D0FIFO/D1FIFO,
but the data transfer direction should be fixed for keeping consistency.
This patch explain about it on renesas_usbhs.h

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --git a/include/linux/usb/renesas_usbhs.h b/include/linux/usb/renesas_usbhs.h
index 547e59c..c5d36c6 100644 (file)
--- a/include/linux/usb/renesas_usbhs.h
+++ b/include/linux/usb/renesas_usbhs.h
@@ -132,6 +132,14 @@ struct renesas_usbhs_driver_param {
         * option:
         *
         * dma id for dmaengine
+        * The data transfer direction on D0FIFO/D1FIFO should be
+        * fixed for keeping consistency.
+        * So, the platform id settings will be..
+        *      .d0_tx_id = xx_TX,
+        *      .d1_rx_id = xx_RX,
+        * or
+        *      .d1_tx_id = xx_TX,
+        *      .d0_rx_id = xx_RX,
         */
        int d0_tx_id;
        int d0_rx_id;