linux-kernel - Re: [PATCH v12 05/11] edma: config: Enable config options for EDMA

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Date:	Fri, 21 Jun 2013 08:52:12 -0500
From:	Joel A Fernandes <agnel.joel@...il.com>
To:	Sekhar Nori <nsekhar@...com>
Cc:	Joel A Fernandes <joelagnel@...com>,
	Tony Lindgren <tony@...mide.com>,
	Matt Porter <matt@...orter.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Benoit Cousson <b-cousson@...com>,
	Russell King <linux@....linux.org.uk>,
	Rob Landley <rob@...dley.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Kridner <jkridner@...gleboard.org>,
	Koen Kooi <koen@...gleboard.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v12 05/11] edma: config: Enable config options for EDMA

On Fri, Jun 21, 2013 at 5:16 AM, Sekhar Nori <nsekhar@...com> wrote:
> On 6/21/2013 2:36 AM, Joel A Fernandes wrote:
>> From: Joel A Fernandes <agnel.joel@...il.com>
>>
>> Build TI_EDMA by default for ARCH_DAVINCI and ARCH_OMAP2PLUS
>>
>> Signed-off-by: Joel A Fernandes <joelagnel@...com>
>
> You should sign-off with author e-mail address.
>
>> ---
>>  arch/arm/Kconfig            |    1 +
>>  arch/arm/mach-omap2/Kconfig |    1 +
>>  drivers/dma/Kconfig         |    2 +-
>>  3 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index b1c66a4..7d58cd9 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -841,6 +841,7 @@ config ARCH_DAVINCI
>>       select HAVE_IDE
>>       select NEED_MACH_GPIO_H
>>       select TI_PRIV_EDMA
>> +     select DMADEVICES
>
> It is generally a bad idea to force select on something that can be
> enabled using menuconfig. Unless used carefully, select causes "unmet
> direct dependency" warnings which folks are already fighting hard to
> fix. This leads to what Russell referred in the past as "select madness" [1]

Are you concerned with bloat issues? I know your point of view but the idea
was to build these options by default for these platforms even though
in some cases
it might not be used. I have seen folks including myself select the wrong
option. Having the build system automatically select the correct option for the
most common cases can be very useful I feel and not require manual
configuration.

> In this particular case, it is perfectly okay to have a DaVinci platform
> without DMA engine support. Drivers figure out they don't have DMA
> support and switch to PIO mode.

Drivers can still use PIO mode if they wish even though DMA is built into the
kernel right.

>>       select USE_OF
>>       select ZONE_DMA
>>       help
>> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
>> index f91b07f..c02f083 100644
>> --- a/arch/arm/mach-omap2/Kconfig
>> +++ b/arch/arm/mach-omap2/Kconfig
>> @@ -17,6 +17,7 @@ config ARCH_OMAP2PLUS
>>       select PROC_DEVICETREE if PROC_FS
>>       select SOC_BUS
>>       select SPARSE_IRQ
>> +     select DMADEVICES
>>       select TI_PRIV_EDMA
>>       select USE_OF
>>       help
>> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
>> index 3215a3c..b2d6f15 100644
>> --- a/drivers/dma/Kconfig
>> +++ b/drivers/dma/Kconfig
>> @@ -216,7 +216,7 @@ config TI_EDMA
>>       depends on ARCH_DAVINCI || ARCH_OMAP
>>       select DMA_ENGINE
>>       select DMA_VIRTUAL_CHANNELS
>> -     default n
>> +     default y
>
> Can't see why DMA support should default to y.
>

For same reason as above.

Thanks,
Joel
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