[PATCH] Avoid delay when initializing USB peripheral by dwc2

[Marek Vasut]

On 3/17/21 4:52 PM, João Loureiro wrote:
> When `usb start` is called on the terminal, 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 (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 host initialization of the device is
> explicitly set as peripheral. The checking is already done similarly
> in the `drivers/usb/gadget/dwc2_udc_otg.c` driver.

[...]

> ---
>   drivers/usb/host/dwc2.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)

A few more things, next time you send a subsequent version of the patch, 
use PATCH vX and document the patch changelog below the diffstat (i.e. 
V2: changed foo because bar).

Also, add tags to subject, for this patch it would be "usb: dwc2:". I 
can fill them in when applying, but in case there is a V3 of this patch, 
update those in your tree too.

Finally, use ./scripts/get_maintainer to find out who to CC. I'm adding 
a few more DWC2 users.

> diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
> index ec643e9f45..43cc2e0433 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 |
> 

[...]