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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/usb/renesas_usbhs.h b/include/linux/usb/renesas_usbhs.h
index 547e59cc00ea..c5d36c65c33b 100644
--- 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;