On Tue, Sep 16, 2014 at 10:13:27PM +0800, Chen-Yu Tsai wrote:
> >> +     /*
> >> +      * sun8i variant requires us to toggle an undocumented register,
> >> +      * as seen in Allwinner's SDK.
> >
> > The BSP I have has this:
> >
> > static void sunxi_dma_hw_init(struct sunxi_dmadev *dev)
> > {
> >         struct sunxi_dmadev *sunxi_dev = dev;
> >
> >         clk_prepare_enable(sunxi_dev->ahb_clk);
> > #ifdef CONFIG_ARCH_SUN8IW3
> >         writel(0x04, sunxi_dev->base + DMA_GATE);
> > #endif
> > }
> >
> > /* All is ok, and open the clock */
> > sunxi_dma_hw_init(sunxi_dev);
> >
> > So I guess we can say that it's not that undocumented :)
> 
> That's right. I meant undocumented in the user manual.
> I did reference the SDK in the comment, didn't I? :)

So something like

writel(DMA_GATE_ENABLE, base->DMA_GATE_REG) wouldn't be too far off :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com