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

[Benjamin Herrenschmidt]

On Sun, 2016-05-08 at 00:54 +0200, Christian Lamparter via Linuxppc-dev 
wrote:
> 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: 

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.

> 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 at 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/\<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 at mbl:~# usb 1-1: new high-speed USB device number 2 using dwc2
> 
> So, what to do?
> 
> Regards,
> Christian
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