[PATCH] Avoid delay when inializing USB peripheral by dwc2.c

[Marek Vasut]

On 3/17/21 12:51 PM, João Loureiro wrote:
> 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";
> };

+CC Lukasz.

The patch looks OK, except you need SoB line, see e.g.
https://www.kernel.org/doc/html/v5.10/process/submitting-patches.html

When in doubt, git format-patch -1 -o /tmp the patch and then run 
./scripts/checkpatch.pl /tmp/00*patch on it, this will tell you what to do.

> Proposed patch below:
> diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
> index ec643e9f45..c6ade25f53 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 |
> 
> ---
> Excuse me if I missed any detail; That's my first patch to u-boot.
> 


-- 
Best regards,
Marek Vasut