linux-kernel - Re: [PATCH] dma: dw: Add suspend and resume handling for PCI mode DW

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Message-ID: <1387450289.1871.240.camel@smile>
Date:	Thu, 19 Dec 2013 12:51:29 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	"Chew, Chiau Ee" <chiau.ee.chew@...el.com>,
	Viresh Kumar <viresh.linux@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.jf.intel.com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dma: dw: Add suspend and resume handling for PCI mode
 DW_DMAC.

On Wed, 2013-12-18 at 21:19 +0530, Vinod Koul wrote:
> On Mon, Dec 16, 2013 at 01:51:47PM +0530, Chew, Chiau Ee wrote:

> > As mentioned by Andy, we are using *_noirq  verion of suspend/resume PM
> > callback whereby the callbacks would be executed after IRQ handlers have been
> > disabled. If using SET_SYSTEM_SLEEP_PM_OPS, it would be the normal
> > suspend/resume PM callback. Looking at the Desginware DMAC platform code
> > (drivers/dma/dw/platform.c), it is using the *_noirq suspend/resume PM
> > callback. Is it advisable to use the normal suspend/resume PM callback instead
> > of *_noirq suspend/PM callback? 
> 
> i dont see a reason why we need the noirq versions

Okay. I imagine the following use case.

For example we have compiled in DMA driver (dw_dmac) along with, for
example, SPI driver.

System was scheduled to go sleep.

An order of calling IIUC might be DMA first, then SPI (since they are
not in parent / child relations).

What was happened when SPI would like to do a DMA transfer and DMA is
going to sleep? I'm trying to understand if this is a case.

> > > How about SET_SYSTEM_SLEEP_PM_OPS instead?
> > 
> > So, we are using *_noirq versions of the functions here. What happened when we switch to normal ones? Any side effects?



-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy

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