linux-kernel - Re: [PATCH v4 8/8] DMA: Freescale: add suspend resume functions for DMA driver

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Message-ID: <1399451493.2677.11.camel@smile.fi.intel.com>
Date:	Wed, 7 May 2014 08:31:34 +0000
From:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:	Hongbo Zhang <hongbo.zhang@...escale.com>
CC:	"Koul, Vinod" <vinod.koul@...el.com>,
	"vkoul@...radead.org" <vkoul@...radead.org>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"scottwood@...escale.com" <scottwood@...escale.com>,
	"leo.li@...escale.com" <leo.li@...escale.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 8/8] DMA: Freescale: add suspend resume functions for
 DMA driver

On Sun, 2014-05-04 at 18:22 +0800, Hongbo Zhang wrote:
> On 05/03/2014 12:46 AM, Vinod Koul wrote:
> > On Fri, Apr 18, 2014 at 04:17:51PM +0800, hongbo.zhang@...escale.com wrote:
> >> From: Hongbo Zhang <hongbo.zhang@...escale.com>
> >>
> >> This patch adds suspend resume functions for Freescale DMA driver.
> >> .prepare callback is used to stop further descriptors from being added into the
> >> pending queue, and also issue pending queues into execution if there is any.
> >> .suspend callback makes sure all the pending jobs are cleaned up and all the
> >> channels are idle, and save the mode registers.
> >> .resume callback re-initializes the channels by restore the mode registers.
> >>
> >> +
> >> +static const struct dev_pm_ops fsldma_pm_ops = {
> >> +	.prepare	= fsldma_prepare,
> >> +	.suspend	= fsldma_suspend,
> >> +	.resume		= fsldma_resume,
> >> +};
> > I think this is not correct. We discussed this sometime back on list. The
> > DMAengine drivers should use late resume and early suspend to ensure they get
> > suspended after clients (who should use normal ones) and resume before them
> >
> OK, will update it like this:
> use .suspend to take place of current .prepare

Could you remove this at all?

Answering to your previous statements I could say that.
Device drivers (DMAc users) that don't implement .suspend callback are
on their own with troubles, you have not to care about them in the DMA
driver.

> use .suspend_late to take place of current .suspend
> use .resume_early to take place of current .resume
> 
> 
> 
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-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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