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

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Date:	Thu, 5 Nov 2015 11:17:50 -0500
From:	Sinan Kaya <okaya@...eaurora.org>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"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 11/5/2015 7:05 AM, Vinod Koul wrote:
> On Wed, Nov 04, 2015 at 09:42:46PM -0500, Sinan Kaya wrote:
>> Here is what I proposed.
>>
>> - a common file that gets compiled into a module that wants to use
>> self-test with a public API. It can be called from driver's probe
>> routine.
>> - the test is independent of my implementation. It uses dmaengine
>> API and should be portable to most drivers.
>> - there *are* still drivers in the kernel that has selftest code
>> embedded inside them. I followed the design pattern from other
>> drivers thinking this must have been a good idea and it paid off for
>> me.
>>
>> As far as I understand, there is interest in doing more than this
>> and reusing the dmatest code for code duplication.
>
> the code that selftest uses to test will be very similar to dmatest code,
> both of these _should_ share this common code so that fixes get done for
> both!
>

OK, I can move the code around and try to combine it if possible.

>> Facts:
>> - Dmatest can be actually configured to run during boot.
>> - Nobody besides the dma driver developer uses dmatest. This leaves
>> holes for regressions that are really hard to debug due to
>> interaction with the rest of the system.
>> - Dmatest doesn't exist in most distribution kernels.
>
> That doesn't mean it is not useful. This line of thought is not quite right.
> You are trying to say dmatest in not important and selftest is. Sorry but
> you are wrong, both are equally important and since both try to test and use
> similar routines (dmaengien API) they need to share the code and not
> duplicate it
>
>> If we want to do something else, I need clear directions. I can
>> remove the self test code completely from my driver. But, I need an
>> equivalent functionality.
>
> Add selftest to dmatest, we need both!
>

OK, do you have any objections to compiling dmatest along with hidma in 
the same module and calling a function from there ? or do you have 
something else in your mind ?

>>
>>>
>>> That part is tricky, you need to do so thru clients, spi/audio/serial etc
>>>
>>
>> My selftest code actually attaches to all slave devices and issues a
>> memcpy command and then detaches from the slave devices.
>
> Not everyone supports memcpy!
>
Right, last time I checked; you can request a DMA channel that supports 
MEMCPY specifically.

-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a 
Linux Foundation Collaborative Project
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