Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756966AbbKRUjO (ORCPT ); Wed, 18 Nov 2015 15:39:14 -0500 Received: from mail-io0-f196.google.com ([209.85.223.196]:33744 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756942AbbKRUjL (ORCPT ); Wed, 18 Nov 2015 15:39:11 -0500 MIME-Version: 1.0 In-Reply-To: <3958456.qUtBLJFy2S@wuerfel> References: <4370741.70D0kgBgnp@wuerfel> <3958456.qUtBLJFy2S@wuerfel> Date: Wed, 18 Nov 2015 14:39:10 -0600 Message-ID: Subject: Re: [PATCH] usb: musb: USB_TI_CPPI41_DMA requires dmaengine support From: Bin Liu To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, George Cherian , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, balbi@ti.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1935 Lines: 52 Hi, On Wed, Nov 18, 2015 at 2:27 PM, Arnd Bergmann 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/