[PATCH] Avoid delay when initializing USB peripherals by dwc2

[João Loureiro]

When `usb start` is called, the dwc2 driver will try to start every
USB device as host first, even if it is explicitly configured as
peripheral in the device tree, as the documentation explains (`dr_mode
= "peripheral"`).

So to avoid an unwanted 15 seconds delay when initializing the usb
(one second per channel = 1s x 15), this patch adds a check to the
initialization, and will skip a host initialization of the device,
when it is explicitly set as peripheral. The checking is already done
similarly in the `drivers/usb/gadget/dwc2_udc_otg.c` driver.

An example device tree entry:
&usb0 {
  compatible = "snps,dwc2";
  status = "okay";
  dr_mode = "peripheral";
};

Signed-off-by: João Loureiro <joaofl at gmail.com>
---
drivers/usb/host/dwc2.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
index ec643e9f45..7990060f3c 100644
--- a/drivers/usb/host/dwc2.c
+++ b/drivers/usb/host/dwc2.c
@@ -21,6 +21,7 @@
#include <asm/io.h>
#include <dm/device_compat.h>
#include <linux/delay.h>
+#include <linux/usb/otg.h>
#include <power/regulator.h>
#include <reset.h>
@@ -1204,7 +1205,13 @@ static int dwc2_init_common(struct udevice
*dev, struct dwc2_priv *priv)
#endif
dwc_otg_core_init(dev);
- dwc_otg_core_host_init(dev, regs);
+
+ if (usb_get_dr_mode(dev_ofnode(dev)) == USB_DR_MODE_PERIPHERAL) {
+ dev_dbg(dev, "USB device %s dr_mode set to %d. Skipping host_init.\n",\
+ dev->name, usb_get_dr_mode(dev_ofnode(dev)));
+ } else {
+ dwc_otg_core_host_init(dev, regs);
+ }
clrsetbits_le32(&regs->hprt0, DWC2_HPRT0_PRTENA |
DWC2_HPRT0_PRTCONNDET | DWC2_HPRT0_PRTENCHNG |
-- 
2.25.1