On 03/10/15 00:25, Arnd Bergmann wrote: > On Thursday 01 October 2015 19:17:27 Mauro Carvalho Chehab wrote: >> > diff --git a/drivers/media/platform/exynos4-is/mipi-csis.c b/drivers/media/platform/exynos4-is/mipi-csis.c >> > index d74e1bec3d86..4b85105dc159 100644 >> > --- a/drivers/media/platform/exynos4-is/mipi-csis.c >> > +++ b/drivers/media/platform/exynos4-is/mipi-csis.c >> > @@ -706,7 +706,8 @@ static irqreturn_t s5pcsis_irq_handler(int irq, void *dev_id) >> > else >> > offset = S5PCSIS_PKTDATA_ODD; >> > >> > - memcpy(pktbuf->data, state->regs + offset, pktbuf->len); >> > + memcpy(pktbuf->data, (u8 __force *)state->regs + offset, >> > + pktbuf->len); >> > pktbuf->data = NULL; >> > > > I think this is what memcpy_toio() is meant for. Exactly memcpy_fromio(). But it's implementation is inefficient on ARCH=arm, memcpy_fromio() will be translated to a loop of readb(), only if an arm sub-architecture provides a processor instruction to access memory by byte. Each readb() also involves a memory barrier. That's all what we wanted to avoid. AFAIR using memcpy_fromio() was causing increase of the copy operation several times comparing to memcpy(). On arm64 it looks better, but this driver is currently used only on arm32. I would prefer to add (void __force *) instead: memcpy(pktbuf->data, (void __force *)state->regs + offset, pktbuf->len); Alternatively, the memset could just be replaced by a loop of u32 reads - __raw_readl(); -- Thanks, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
