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

[Benjamin Herrenschmidt <benh@au1.ibm.com>]

On Sun, 2016-05-08 at 13:44 +0200, Christian Lamparter wrote:
> On Sunday, May 08, 2016 08:40:55 PM Benjamin Herrenschmidt wrote:
> > 
> > On Sun, 2016-05-08 at 00:54 +0200, Christian Lamparter via Linuxppc-dev 
> > wrote:
> > > 
> > > 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: 
> > Smells like the APM implementation is little endian. You might need to
> > use a flag to indicate what endian to use instead and set it
> > appropriately based on some DT properties.
> I tried. As per common-properties[0], I added little-endian; but it has no
> effect. I looked in dwc2_driver_probe and found no way of specifying the
> endian of the device. It all comes down to the dwc2_readl & dwc2_writel
> accessors. These - sadly - have been hardwired to use __raw_readl and
> __raw_writel. So, it's always "native-endian". While common-properties
> says little-endian should be preferred.

Right, I meant, you should produce a patch adding a runtime test inside
those functions based on a device-tree property, a bit like we do for
some of the HCDs like OHCI, EHCI etc...

Cheers,
Ben.

> > 
> > > 
> > > 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 <a.seppala@gmail.com>
> > > 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/\/dwc2_readl/g" *.c hcd.h hw.h
> > >     sed -i "s/\/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
> 
> [0] 
> 
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