linux-kernel - Re: [PATCH V2 2/3] dmaselftest: add memcpy selftest support functions

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Date:	Mon, 2 Nov 2015 23:44:23 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	Sinan Kaya <okaya@...eaurora.org>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 2/3] dmaselftest: add memcpy selftest support functions

On Mon, Nov 2, 2015 at 10:30 PM, Vinod Koul <vinod.koul@...el.com> wrote:
> On Mon, Nov 02, 2015 at 11:18:37PM -0500, Sinan Kaya wrote:
>>
>>
>> On 11/2/2015 11:15 PM, Vinod Koul wrote:
>> >On Mon, Nov 02, 2015 at 01:07:38AM -0500, Sinan Kaya wrote:
>> >>This patch adds supporting utility functions
>> >>for selftest. The intention is to share the self
>> >>test code between different drivers.
>> >>
>> >>Supported test cases include:
>> >>1. dma_map_single
>> >>2. streaming DMA
>> >>3. coherent DMA
>> >>4. scatter-gather DMA
>> >
>> >This seems quite similar to dmatest, any reason why you cannot use/enhance
>> >that?
>> >
>> Dmatest is a standalone kernel module intended for stress testing
>> DMA engines from userspace with N number of threads and M size
>> combinations etc.
>>
>> This one; on the other hand, is selftest to verify hardware is
>> working as expected during power up.
>>
>> Almost all DMA engine drivers come with some sort of selftest code
>> called from probe. I followed the same design pattern.
>
> which ones ?
>
>>
>> I think the goal is to remove the duplicate self test code in all
>> drivers over time.
>
> and what prevents us from having common selftest plus dmatest code. Most of
> the code here to do selftest is _same_ dmaengine routine code used in
> dmatest
>
> We can have common code which is used for dmatest as well as selftest. I do
> not want to see same code duplicated..

Originally ioatdma and iop-adma had local self tests before Haavard
created dmatest.  I agree having the drivers also do a test each boot
is redundant, but then again dmatest is not automatic and I saw the
local self test catch an interrupt setup regression.

Maybe you could arrange for drivers to do a quick autorun through
dmatest on load if dmatest is enabled, but otherwise load without
testing?  Just my 2 cents from a dmaengine spectator.
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