linux-kernel - Re: [PATCH v5 05/12] mtd: pxa3xx_nand: rework flash detection and timing setup

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Message-ID: <20150520135531.GK22054@kwain>
Date:	Wed, 20 May 2015 15:55:31 +0200
From:	Antoine Tenart <antoine.tenart@...e-electrons.com>
To:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	sebastian.hesselbarth@...il.com, dwmw2@...radead.org,
	computersforpeace@...il.com, boris.brezillon@...e-electrons.com,
	zmxu@...vell.com, jszhang@...vell.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/12] mtd: pxa3xx_nand: rework flash detection and
 timing setup

On Sat, May 16, 2015 at 06:23:23PM -0300, Ezequiel Garcia wrote:
> On 05/12/2015 11:39 AM, Antoine Tenart wrote:
> > On Mon, May 11, 2015 at 07:10:56PM -0300, Ezequiel Garcia wrote:
> >>
> >> On 05/11/2015 11:58 AM, Antoine Tenart wrote:
> >> [..]
> >>> -
> >>> -	/* calculate flash information */
> >>> -	host->read_id_bytes = (f->page_size == 2048) ? 4 : 2;
> >>> -
> >>
> >> [..]
> >>> @@ -1732,6 +1669,7 @@ static int alloc_nand_resource(struct platform_device *pdev)
> >>>  		host->mtd = mtd;
> >>>  		host->cs = cs;
> >>>  		host->info_data = info;
> >>> +		host->read_id_bytes = 4;
> >>
> >> Are you sure this is correct? The value is set according to the page
> >> size before this patch.
> > 
> > Before reading the ID, the pxa3xx driver uses a default configuration,
> > builtin_flash_types[0], which defines a page size of 2048 leading to set
> > host->read_id_bytes to 4.
> > 
> > I'm using this default value here.
> > 
> > There might be an issue, as host->read_id_bytes isn't updated after
> > reading the ID (and getting the actual page size). I don't know if this
> > can be a problem. I can modify pxa3xx_nand_config_flash() to update
> > host->read_id_bytes if needed. What do you think?
> > 
> 
> Well, once the device is detected, READ_ID shouldn't be used, so I'm not
> sure what's the point of that.

I don't think there's a need to update read_id_bytes once the device is
detected. Why don't we stay with 4?

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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