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usb: gadget: pxa25x_udc: document endianess better

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When I wrote the cleanup patch series, it was not clear how
exactly big-endian mode works on ixp4xx, and whether the driver
was doing this correctly. After discussing with Krzysztof Hałasa,
this has been clarified, so I can update the comment let pxa25x
big-endian (which we don't support) work the same way as ixp4xx.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
This commit is contained in:
Arnd Bergmann 2016-02-17 16:51:40 +01:00 committed by Felipe Balbi
parent 62a6abdd42
commit a9458a3b33
1 changed files with 7 additions and 7 deletions
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14
drivers/usb/gadget/udc/pxa25x_udc.c
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@ -289,14 +289,14 @@ static void pullup_on(void)
mach->udc_command(PXA2XX_UDC_CMD_CONNECT);
}
#if defined(CONFIG_ARCH_IXP4XX) && defined(CONFIG_CPU_BIG_ENDIAN)
#if defined(CONFIG_CPU_BIG_ENDIAN)
/*
* not sure if this is the correct behavior on ixp4xx in both
* bit-endian and little-endian modes, but it's what the driver
* has always done using direct pointer dereferences:
* We assume that there is a byteswap done in hardware at the
* MMIO register that matches what the CPU setting is, so we
* never swap in software.
* IXP4xx has its buses wired up in a way that relies on never doing any
* byte swaps, independent of whether it runs in big-endian or little-endian
* mode, as explained by Krzysztof Hałasa.
*
* We only support pxa25x in little-endian mode, but it is very likely
* that it works the same way.
*/
static inline void udc_set_reg(struct pxa25x_udc *dev, u32 reg, u32 val)
{