From: Arnd Bergmann Date: Wed, 17 Feb 2016 15:51:40 +0000 (+0100) Subject: usb: gadget: pxa25x_udc: document endianess better X-Git-Tag: v4.6-rc1~117^2~4^2~60 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=a9458a3b33ea1a00fc9d1beb3c0bb1c2d18855c9;p=linux.git usb: gadget: pxa25x_udc: document endianess better 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 Signed-off-by: Felipe Balbi --- diff --git a/drivers/usb/gadget/udc/pxa25x_udc.c b/drivers/usb/gadget/udc/pxa25x_udc.c index 6d3acbf3b311..a238da906115 100644 --- a/drivers/usb/gadget/udc/pxa25x_udc.c +++ b/drivers/usb/gadget/udc/pxa25x_udc.c @@ -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) {