On Wed, May 17, 2017 at 11:16 PM, Chris Packham <chris.pack...@alliedtelesis.co.nz> wrote: > On 18/05/17 06:18, Borislav Petkov wrote: > One thing I would like confirmation on is is in_le32 -> ioread32 the > correct change? I tossed up between ioread32 and readl. Looking at > mv643xx_eth.c which supports both the MV643XX and Orion it's using readl > so perhaps I should be using that.
There is no easy answer: on powerpc, readl is used for PCI, while in_le32 is used for on-chip devices, so in_le32 is the right one in principle. The main difference is that readl can work with CONFIG_EEH on pseries, but in_le32 is cheaper. On ARM and most other architectures, readl is used for both PCI and on-chip devices, so that's what portable code tends to use. ioread32 is required to behave the same way as readl on all __iomem pointers returned from ioremap(), but is an extern function on powerpc and can be more expensive when CONFIG_GENERIC_IOMAP is set. I'd go with readl() in this case. Arnd