usb: dwc2: Always disable regulators on driver teardown

If the dwc2 driver fails to probe after having enabled the regulators,
it ends up being unregistered with regulators enabled, something the
core regulator code is legitimately upset about:

   dwc2 ff400000.usb: supply vusb_d not found, using dummy regulator
   dwc2 ff400000.usb: supply vusb_a not found, using dummy regulator
   dwc2 ff400000.usb: dwc2_core_reset: HANG! AHB Idle timeout GRSTCTL GRSTCTL_AHBIDLE
   WARNING: CPU: 2 PID: 112 at drivers/regulator/core.c:2074 _regulator_put.part.0+0x16c/0x174
   Modules linked in: dwc2(E+) dwc3(E) udc_core(E) rtc_hym8563(E) dwmac_generic(E) ulpi(E) usbcore(E) dwc3_meson_g12a(E) roles(E) meson_gx_mmc(E+) i2c_meson(E) mdio_mux_meson_g12a(E) mdio_mux(E) dwmac_meson8b(E) stmmac_platform(E) stmmac(E) mdio_xpcs(E) phylink(E) of_mdio(E) fixed_phy(E) libphy(E) pwm_regulator(E) fixed(E)
   CPU: 2 PID: 112 Comm: systemd-udevd Tainted: G            E     5.9.0-rc4-00102-g423583bc8cf9 #1840
   Hardware name: amlogic w400/w400, BIOS 2020.04 05/22/2020
   pstate: 80400009 (Nzcv daif +PAN -UAO BTYPE=--)
   pc : _regulator_put.part.0+0x16c/0x174
   lr : regulator_bulk_free+0x6c/0x9c
   sp : ffffffc012353820
   x29: ffffffc012353820 x28: ffffff805a4b7000
   x27: ffffff8059c2eac0 x26: ffffff8059c2e810
   x25: ffffff805a4b7d00 x24: ffffffc008cf3028
   x23: ffffffc011729ef8 x22: ffffff807e2761d8
   x21: ffffffc01171df78 x20: ffffff805a4b7700
   x19: ffffff805a4b7700 x18: 0000000000000030
   x17: 0000000000000000 x16: 0000000000000000
   x15: ffffff807ea8d178 x14: 3935312820435455
   x13: 2038323a36313a37 x12: ffffffffffffffff
   x11: 0000000000000040 x10: 0000000000000007
   x9 : ffffffc0106f77d0 x8 : ffffffffffffffe0
   x7 : ffffffffffffffff x6 : 0000000000017702
   x5 : ffffff805a4b7400 x4 : 0000000000000000
   x3 : ffffffc01171df78 x2 : ffffff807ea8cc40
   x1 : 0000000000000000 x0 : 0000000000000001
   Call trace:
    _regulator_put.part.0+0x16c/0x174
    regulator_bulk_free+0x6c/0x9c
    devm_regulator_bulk_release+0x28/0x3c
    release_nodes+0x1c8/0x2c0
    devres_release_all+0x44/0x6c
    really_probe+0x1ec/0x504
    driver_probe_device+0x100/0x170
    device_driver_attach+0xcc/0xd4
    __driver_attach+0xb0/0x17c
    bus_for_each_dev+0x7c/0xd4
    driver_attach+0x30/0x3c
    bus_add_driver+0x154/0x250
    driver_register+0x84/0x140
    __platform_driver_register+0x54/0x60
    dwc2_platform_driver_init+0x2c/0x1000 [dwc2]
    do_one_initcall+0x54/0x2d0
    do_init_module+0x68/0x29c

In order to fix this, tie the regulator disabling to the teardown
process by registering a devm action callback. This makes sure that
the regulators are disabled at the right time (just before they are
released).

Cc: Minas Harutyunyan <hminas@synopsys.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200914130634.2424496-1-maz@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/platform.c

@@ -121,6 +121,13 @@ static int dwc2_get_dr_mode(struct dwc2_hsotg *hsotg)
 	return 0;
 }
 
+static void __dwc2_disable_regulators(void *data)
+{
+	struct dwc2_hsotg *hsotg = data;
+
+	regulator_bulk_disable(ARRAY_SIZE(hsotg->supplies), hsotg->supplies);
+}
+
 static int __dwc2_lowlevel_hw_enable(struct dwc2_hsotg *hsotg)
 {
 	struct platform_device *pdev = to_platform_device(hsotg->dev);
@@ -131,6 +138,11 @@ static int __dwc2_lowlevel_hw_enable(struct dwc2_hsotg *hsotg)
 	if (ret)
 		return ret;
 
+	ret = devm_add_action_or_reset(&pdev->dev,
+				       __dwc2_disable_regulators, hsotg);
+	if (ret)
+		return ret;
+
 	if (hsotg->clk) {
 		ret = clk_prepare_enable(hsotg->clk);
 		if (ret)
@@ -186,10 +198,7 @@ static int __dwc2_lowlevel_hw_disable(struct dwc2_hsotg *hsotg)
 	if (hsotg->clk)
 		clk_disable_unprepare(hsotg->clk);
 
-	ret = regulator_bulk_disable(ARRAY_SIZE(hsotg->supplies),
-				     hsotg->supplies);
-
-	return ret;
+	return 0;
 }
 
 /**