Dear Arnd, On Fri, 14 Feb 2014 01:09:44 -0800 Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Friday 14 February 2014 15:54:38 Jisheng Zhang wrote: > > Hi all, > > > > The writel/readl is too expensive especially on Cortex A9 w/ outer L2 > > cache. This introduce i2c read/write error on Marvell Berlin SoCs when > > there are L2 cache maintenance operations at the same time. > > > > In our internal berlin bsp, we just replaced readl/writel with the relaxed > > version. But AFAIK, the "relaxed" version doesn't exist on all > > architectures. How to handle this issue? > > In case of i2c-designware, this is safe because that driver does not perform > DMA. In other drivers, you may have to be more careful, to ensure that all > MMIO is serialized with DMA operations performed by the driver. > > > Any suggestions are appreciated. > > I would definitely welcome a patch that adds a default _relaxed > implementation to include/linux/io.h, like this: > > #ifndef readb_relaxed > #define readb_relaxed(p) readb(p) > #endif > > and then adds "#define readb_relaxed(p) readb_relaxed(p)" etc. to all > architectures that have a non-macro definition for readb. Thanks for the suggestions. I'll try to send out one RFC patch. Thanks, Jisheng -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
