Subject: usb: dwc2: regression on MyBook Live Duo / Canyonlands since 4.3.0-rc4

From: Christian Lamparter <[email-masked]>
Date: Sun, 08 May 2016 00:54:44 +0200

Hello,

I've been looking in getting the MyBook Live Duo's USB OTG port
to function. The SoC is a APM82181. Which has a PowerPC 464 core
and related to the supported canyonlands architecture in arch/powerpc/.

Currently in -next the dwc2 module doesn't load: 

dwc2 4bff80000.usbotg: dwc2_core_reset() HANG! AHB Idle GRSTCTL=80
dwc2 4bff80000.usbotg: Bad value for GSNPSID: 0x0a29544f

Looking at the Bad GSNPSID value: 0x0a29544f. It is obvious that
this is an endian problem. git finds this patch:

commit 95c8bc3609440af5e4a4f760b8680caea7424396
Author: Antti Seppälä <[email-masked]>
Date:   Thu Aug 20 21:41:07 2015 +0300

    usb: dwc2: Use platform endianness when accessing registers

    This patch is necessary to access dwc2 registers correctly on big-endian
    systems such as the mips based SoCs made by Lantiq. Then dwc2 can be
    used to replace ifx-hcd driver for Lantiq platforms found e.g. in
    OpenWrt.
    
    The patch was autogenerated with the following commands:
    $EDITOR core.h
    sed -i "s/\<readl\>/dwc2_readl/g" *.c hcd.h hw.h
    sed -i "s/\<writel\>/dwc2_writel/g" *.c hcd.h hw.h
    
    Some files were then hand-edited to fix checkpatch.pl warnings about
    too long lines.

which unfortunately, broke the USB-OTG port on the MyBook Live Duo.
Reverting to the readl / writel:

--- 
diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
index 3c58d63..c021c1f 100644
--- a/drivers/usb/dwc2/core.h
+++ b/drivers/usb/dwc2/core.h
@@ -66,7 +66,7 @@
 
 static inline u32 dwc2_readl(const void __iomem *addr)
 {
-	u32 value = __raw_readl(addr);
+	u32 value = readl(addr);
 
 	/* In order to preserve endianness __raw_* operation is used. Therefore
 	 * a barrier is needed to ensure IO access is not re-ordered across
@@ -78,7 +78,7 @@ static inline u32 dwc2_readl(const void __iomem *addr)
 
 static inline void dwc2_writel(u32 value, void __iomem *addr)
 {
-	__raw_writel(value, addr);
+	writel(value, addr);
 
 	/*
 	 * In order to preserve endianness __raw_* operation is used. Therefore

---

restores the dwc-otg port to full working order:
dwc2 4bff80000.usbotg: Specified GNPTXFDEP=1024 > 256
dwc2 4bff80000.usbotg: EPs: 3, shared fifos, 2042 entries in SPRAM
dwc2 4bff80000.usbotg: DWC OTG Controller
dwc2 4bff80000.usbotg: new USB bus registered, assigned bus number 1
dwc2 4bff80000.usbotg: irq 33, io mem 0x00000000
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
root@mbl:~# usb 1-1: new high-speed USB device number 2 using dwc2

So, what to do?

Regards,
Christian