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

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Message-ID: <20150520140416.GM22054@kwain>
Date:	Wed, 20 May 2015 16:04:16 +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 Wed, May 20, 2015 at 10:56:28AM -0300, Ezequiel Garcia wrote:
> 
> 
> On 05/20/2015 10:55 AM, Antoine Tenart wrote:
> > 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?
> > 
> 
> Sure, that's exactly what I was saying.

Great! I'll update.

Antoine

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