stm32mp1xx: use of reg11, reg18 and vdd_usb rails

[Sean Nyekjaer]

Hi all,

We are using the osd32mp1 SIP module [0].
We are seeing some hardware get’s fried inside the SIP module.
It’s somewhat traced down to the usb controller/phy/regulator.

With this device tree[1]. We have noticed during boot the reg18 is toggled on and off
without vdd_usb being turned off before reg18 as required in the data sheet[2], section 3.8.1:
VDD3V3_USBHS must not be present unless VDDA1V8_REG is present, otherwise permanent 
STM32MP157C/F damage could occur. Must be ensured by PMIC ranking order or with
external component in case of discrete component power supply implementation.

It’s happens because the something is already uses the vdd_usb, it’s both the drivers/phy/st/phy-stm32-usbphyc.c
and drivers/regulator/stm32-pwr.c that consumes it.

I can fix it by removing the vdd_usb from the usb33 supply[3]:
The stm32-pwr.c is (to me) rather weird, as it exposes the usb33 as a regulator when in fact it’s a detection pin.
Is that done on purpose?

I would like introduce a error in the stm32-pwr.c if something is trying to power off reg18 with usb33 present?
Would it be okay to return -EBUSY? Or even -ESMOKE? :)

Or is it better to do it in phy-stm32-usbphyc.c[4]?

/Sean

[0]: https://octavosystems.com/octavo_products/osd32mp15x/
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/st/stm32mp157c-osd32mp1-red.dts
[2]: https://www.st.com/resource/en/datasheet/stm32mp157c.pdf
[3]:
diff --git a/arch/arm/boot/dts/st/stm32mp157c-osd32mp1-red.dts b/arch/arm/boot/dts/st/stm32mp157c-osd32mp1-red.dts
index 527c33be66cc..0d67006806c4 100644
--- a/arch/arm/boot/dts/st/stm32mp157c-osd32mp1-red.dts
+++ b/arch/arm/boot/dts/st/stm32mp157c-osd32mp1-red.dts
@@ -149,7 +149,6 @@ &m_can1 {

 &pwr_regulators {
        vdd-supply = <&vdd>;
-       vdd_3v3_usbfs-supply = <&vdd_usb>;
 };

 &rtc {
[4]:
diff --git a/drivers/phy/st/phy-stm32-usbphyc.c b/drivers/phy/st/phy-stm32-usbphyc.c
index d5e7e44000b5..58fcc3099803 100644
--- a/drivers/phy/st/phy-stm32-usbphyc.c
+++ b/drivers/phy/st/phy-stm32-usbphyc.c
@@ -188,8 +188,18 @@ static int stm32_usbphyc_regulators_enable(struct stm32_usbphyc *usbphyc)

 static int stm32_usbphyc_regulators_disable(struct stm32_usbphyc *usbphyc)
 {
+       struct stm32_usbphyc_phy *usbphyc_phy;
        int ret;

+       for (port = 0; port < usbphyc->nphys; port++) {
+               usbphyc_phy = usbphyc->phys[port];
+
+               if(regulator_is_enabled(usbphyc_phy->phy->pwr)) {
+                       pr_err("%s: phy is powered not allowed to switch off regulator\n", __func__);
+                       return -EBUSY;
+               }
+       }
+
        ret = regulator_disable(usbphyc->vdda1v8);
        if (ret)
                return ret;