linux-kernel - RE: [EXT] Re: [PATCH] mtd: spi-nor: Add prep/unprep for spi_nor

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Date:   Thu, 6 Jun 2019 22:33:29 +0000
From:   Han Xu <han.xu@....com>
To:     "Tudor.Ambarus@...rochip.com" <Tudor.Ambarus@...rochip.com>,
        "cyrille.pitchen@...ev4u.fr" <cyrille.pitchen@...ev4u.fr>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>
CC:     "boris.brezillon@...e-electrons.com" 
        <boris.brezillon@...e-electrons.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "kdasu.kdev@...il.com" <kdasu.kdev@...il.com>,
        "richard@....at" <richard@....at>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>
Subject: RE: [EXT] Re: [PATCH] mtd: spi-nor: Add prep/unprep for
 spi_nor_resume



> -----Original Message-----
> From: Tudor.Ambarus@...rochip.com <Tudor.Ambarus@...rochip.com>
> Sent: Thursday, June 6, 2019 12:46 AM
> To: Han Xu <han.xu@....com>; cyrille.pitchen@...ev4u.fr;
> marek.vasut@...il.com
> Cc: boris.brezillon@...e-electrons.com; f.fainelli@...il.com;
> kdasu.kdev@...il.com; richard@....at; linux-kernel@...r.kernel.org;
> linux-mtd@...ts.infradead.org; dl-linux-imx <linux-imx@....com>;
> computersforpeace@...il.com
> Subject: [EXT] Re: [PATCH] mtd: spi-nor: Add prep/unprep for
> spi_nor_resume
> 
> Caution: EXT Email
> 
> Hi, Han,
> 
> On 04/25/2019 12:08 AM, Han Xu wrote:
> > External E-Mail
> >
> >
> > In the new implemented spi_nor_resume function, the spi_nor_init()
> > should be braced by prep/unprep functions._
> >
> 
> Would you please explain why this is needed? Have you tried a
> suspend/resume cycle while a write was in progress and it failed?

Same as all other functions that hooked up with mtd ops, such as
_read/_write/_lock/_unlock, the _resume function also need to call the
lower level controller's prep/unprep functions to properly handle runtime
pm and mutex.

I didn't try suspend/resume during writing, but found accessing registers
without enabling clock when system resumed.

> 
> Thanks,
> ta