Messages in this thread | | | Date | Wed, 18 Nov 2015 14:39:10 -0600 | Subject | Re: [PATCH] usb: musb: USB_TI_CPPI41_DMA requires dmaengine support | From | Bin Liu <> |
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Hi,
On Wed, Nov 18, 2015 at 2:27 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Wednesday 18 November 2015 12:29:27 Bin Liu wrote: >> > diff --git a/drivers/usb/musb/Kconfig b/drivers/usb/musb/Kconfig >> > index 1f2037bbeb0d..45c83baf675d 100644 >> > --- a/drivers/usb/musb/Kconfig >> > +++ b/drivers/usb/musb/Kconfig >> > @@ -159,7 +159,7 @@ config USB_TI_CPPI_DMA >> > >> > config USB_TI_CPPI41_DMA >> > bool 'TI CPPI 4.1 (AM335x)' >> > - depends on ARCH_OMAP >> > + depends on ARCH_OMAP && DMADEVICES >> > select TI_CPPI41 >> >> I am not sure what the generic policy is, but instead of hiding >> USB_TI_CPPI41_DMA if DMADEVICES is disabled, I'd like to enable >> DMADEVICES if USB_TI_CPPI41_DMA is enabled, from user experience >> perspective. > > General policy is that you should not 'select' a symbol that is > also user-visible, as that tends to cause dependency loops and > other problems when something is enabled without the user being > aware of that.
Understood. Thanks. I am okay with this patch.
> > Ideally we should remove the 'select TI_CPPI41' here as well, but > what we could do instead is to make that a silent symbol and remove > the prompt so it always gets enabled implicitly when USB_TI_CPPI41_DMA > and DMADEVICES are both enabled.
But what if DMADEVICES was disabled and USB_TI_CPPI41_DMA was enabled? I would think I had CPPI fully enabled for MUSB, but it didn't because TI_CPPI41 was disabled.
I would think this patch is the test option so far, we might have to document somewhere that to dmaengine has to be enabled to use MUSB CPPI, but I am not sure where the best place is to document...
Regards, -Bin.
> > Arnd
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