Re: [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