> Subject: Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx > > On Tuesday 30 September 2014 20:39:34 Peter Chen wrote: > > 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? > > No, that is just the current definition on ARM32 with > CONFIG_ARCH_MULTIPLATFORM, and that is going to change soon to be DT > aware. > dma_set_mask_and_coherent() is supposed to check whether the platform > can support the respective mask and return an error if it cannot. > > > - 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"? > > dma_coerce_mask_and_coherent() will hardcode the dma mask and override > whatever the platform says is necessary. > So, we should use dma_set_mask_and_coherent() in most of cases in device driver, and use dma_coerce_mask_and_coherent() only when the device's dma_mask is wrong? Peter -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
