linux-kernel - Re: [PATCHv3 5/7] dmaengine: dw_dmac: add PCI part of the driver

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Date:	Wed, 24 Oct 2012 16:43:38 +0530
From:	Vinod Koul <vkoul@...radead.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	vinod.koul@...el.com,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Arnd Bergmann <arnd.bergmann@...aro.org>,
	linux-kernel@...r.kernel.org,
	spear-devel <spear-devel@...t.st.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCHv3 5/7] dmaengine: dw_dmac: add PCI part of the driver

On Mon, 2012-10-08 at 18:57 +0530, Viresh Kumar wrote:
> I agree that there are some parts of your approach which might be having
> few advantages. But it is actually adding more complexity without much
> need of it. Logically speaking, we never had two devices for the same
> dma controller. We are adding them just to have pci over platform.. Which
> would mean the system become more and more complex..
> 
> So, during run time...
> - there will be two device-driver binding loops.. Once for pci and then for
>   platform
> - In suspend/resume... two devices will get into suspend, instead of one..
> - There might be other frameworks in kernel.. which react on struct device
>    basis... they will get affected too..
> - You have larger image size for pci case. as you compile platform too..
> 
> Just try to think from this perspective... we dont have two hardware devices
> in the system.... Ideally speaking there must be a struct device associated
> with a hardware device...
> 
> @Arnd/Vinod: Can you guys throw some more light here.. on the adv/disadv
> of both the approaches?
I am worried about those tow. Runtime PM handlers in case PCI devices
make life a lot easier am not sure what support will be there for
platform devices in other systems.
Also next version of this h/w on our systems is bringing subtle changes
so having them separate seemed to me a better idea.


-- 
Vinod Koul
Intel Corp.

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