On Tue, Sep 30, 2014 at 12:03:42PM +0200, Arnd Bergmann wrote: > On Tuesday 30 September 2014 08:12:07 Peter Chen wrote: > > > + > > > + if (dev->of_node) { > > > + ret = ci_hdrc_usb2_dt_probe(dev, ci_pdata); > > > + if (ret) > > > + goto clk_err; > > > + } else { > > > + ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)); > > > + if (ret) > > > + goto clk_err; > > > + } > > > > My suggestion: > > > > - call dma_coerce_mask_and_coherent(&dev->dev, DMA_BIT_MASK(32)) for both > > dt and non-dt > > No, as I explained before, hardcoding the dma mask is always wrong, don't > do that. Call dma_set_mask_and_coherent and check the return value. > It's not wrong to do that for both DT and ATAGS. > Thanks, Arnd. I had not thought setting dma mask is so complicated, yes, it should check the return value, two things to confirm: - dma_coerce_mask_and_coherent or dma_set_mask_and_coherent, the only difference of these two API is the first one do "dev->dma_mask = &dev->coherent_dma_mask;" The reason you suggest choosing dma_set_mask_and_coherent is you do not want assign dev->dma_mask? - The second parameter for dma_set_mask_and_coherent is DMA_BIT_MASK(32), is it ok? I just a little confused of what's the operation is "hardcoding the dma mask"? -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html