Subject: Re: [PATCH 5/8 v2] powerpc/mpc5121: add USB host support

From: Jan Andersson <[email-masked]>
Date: Wed, 27 Jan 2010 13:36:12 +0100

Anatolij Gustschin wrote:
> @@ -259,6 +305,11 @@ static int ehci_fsl_setup(struct usb_hcd *hcd)
>  {
>  	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
>  	int retval;
> +	struct fsl_usb2_platform_data *pdata;
> +
> +	pdata = hcd->self.controller->platform_data;
> +	ehci->big_endian_desc = pdata->big_endian_desc;
> +	ehci->big_endian_mmio = pdata->big_endian_mmio;

I recently posted some questions to linux-usb@vger about big_endian_mmio 
and the definition of the HC_LENGTH and HC_VERSION macros. The thread 
can be found here: http://marc.info/?l=linux-usb&m=126441448626924&w=2

The EHCI specification defines the CAPLENGTH register as an 8-bit 
register at byte offset 0 and HCIVERSION as a 16-bit register at byte 
offset 2. Performing a 32-bit read on a big endian system should 
therefore results in the following organisation (MSB .. LSB):
CAPLENGTH : RESERVED : HCIVERSION

The macros for reading CAPLENGTH and HCIVERSION (defined in 
include/linux/usb/ehci-def.h) look like:

#define HC_LENGTH(p)		(((p)>>00)&0x00ff)	/* bits 7:0 */
#define HC_VERSION(p)		(((p)>>16)&0xffff)	/* bits 31:16 */

That is, they select the registers as they were organized within the 
word according to little endian. Is this not a problem for your 
controller/driver?

Best regards,
   Jan