usb: gadget: renesas_usbhs: tidyup INTENB0 method

This patch tidyup Interrupt Enable Register 0 (INTENB0)
which has relationship with picky BEMPENB/BRDYENB.

 - add explain comment
 - ignore nonsense 0 write case

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

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/usb/renesas_usbhs/mod.c b/drivers/usb/renesas_usbhs/mod.c
index 621f6cc50db6..74ef49e7dd5f 100644
--- a/drivers/usb/renesas_usbhs/mod.c
+++ b/drivers/usb/renesas_usbhs/mod.c
@@ -292,6 +292,14 @@ void usbhs_irq_callback_update(struct usbhs_priv *priv, struct usbhs_mod *mod)
         u16 intenb0 = 0;
         struct usbhs_mod_info *info = usbhs_priv_to_modinfo(priv);
 
+        /*
+         * BEMPENB/BRDYENB are picky.
+         * below method is required
+         *
+         *  - clear  INTSTS0
+         *  - update BEMPENB/BRDYENB
+         *  - update INTSTS0
+         */
         usbhs_write(priv, INTENB0, 0);
 
         usbhs_write(priv, BEMPENB, 0);
@@ -324,5 +332,6 @@ void usbhs_irq_callback_update(struct usbhs_priv *priv, struct usbhs_mod *mod)
                 }
         }
 
-        usbhs_write(priv, INTENB0, intenb0);
+        if (intenb0)
+                usbhs_write(priv, INTENB0, intenb0);
 }