linux-kernel - Re: [PATCH v3 5/9] mtd: nand: add sunxi NAND flash controller support

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Date:	Tue, 20 May 2014 21:36:59 +0200
From:	Boris BREZILLON <b.brezillon.dev@...il.com>
To:	Brian Norris <computersforpeace@...il.com>
CC:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Emilio López <emilio@...pez.com.ar>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Rob Herring <robherring2@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Grant Likely <grant.likely@...aro.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, dev@...ux-sunxi.org,
	linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 5/9] mtd: nand: add sunxi NAND flash controller support


On 20/05/2014 21:21, Brian Norris wrote:
> On Tue, May 20, 2014 at 11:49:42AM -0700, Brian Norris wrote:
>> On Fri, May 09, 2014 at 06:47:22PM +0200, Boris BREZILLON wrote:
>>> On 09/05/2014 18:03, Ezequiel Garcia wrote:
>>>> On 12 Mar 07:07 PM, Boris BREZILLON wrote:
>>>>> --- /dev/null
>>>>> +++ b/drivers/mtd/nand/sunxi_nand.c
>>>>> @@ -0,0 +1,1276 @@
>> ...
>>>>> +static int sunxi_nand_ecc_init(struct mtd_info *mtd, struct nand_ecc_ctrl *ecc,
>>>>> +			       struct device_node *np)
>>>>> +{
>>>>> +	struct nand_chip *nand = mtd->priv;
>>>>> +	int ecc_step_size, ecc_strength;
>>>>> +	int ret;
>>>>> +
>>>>> +	ecc_step_size = of_get_nand_ecc_step_size(np);
>>>>> +	ecc_strength = of_get_nand_ecc_strength(np);
>>>>> +	if (ecc_step_size > 0 && ecc_strength > 0) {
>>>>> +		ecc->size = ecc_step_size;
>>>>> +		ecc->strength = ecc_strength;
>>>>> +	} else {
>>>>> +		ecc->size = nand->ecc_step_ds;
>>>>> +		ecc->strength = nand->ecc_strength_ds;
>>>>> +	}
>>>>> +
>>>> Shouldn't you check the devicetree value is not weaker than the ONFI-obtained?
>>> I can definitely do that.
>> You can do that here, but take a look at the discussion Ezequiel and I
>> had about this:
>>
>>   http://thread.gmane.org/gmane.linux.drivers.devicetree/67462
>>
>> We probably don't want to be doing anything drastic like overriding the
>> device tree configuration. Instead, we might want to stick a warning
>> into the core nand_base code that does the proper comparison of the
>> '*_ds' values with the actual values chosen in
>> chip->ecc->{size,strength}. The comparison is kind of subtle, actually,
>> so it'd be good to do it exactly once for everyone.

Fair enough, I'll follow your suggestions on this specific point ;)

> I forgot, Ezequiel already submitted this. I'll look at it soon:
>
>   http://patchwork.ozlabs.org/patch/348901/

Thanks for pointing this out.


>
> Brian

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