linux-kernel - Re: [RFC PATCH v2 08/14] mtd: nand: add sunxi NAND flash controller support

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Date:	Wed, 29 Jan 2014 20:02:52 +0100
From:	Boris BREZILLON <b.brezillon.dev@...il.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
CC:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Rob Landley <rob@...dley.net>,
	Russell King <linux@....linux.org.uk>,
	David Woodhouse <dwmw2@...radead.org>,
	Grant Likely <grant.likely@...aro.org>,
	Brian Norris <computersforpeace@...il.com>,
	Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, dev@...ux-sunxi.org
Subject: Re: [RFC PATCH v2 08/14] mtd: nand: add sunxi NAND flash controller
 support

Le 29/01/2014 18:56, Jason Gunthorpe a écrit :
> On Wed, Jan 29, 2014 at 03:34:18PM +0100, Boris BREZILLON wrote:
>
>> +static int sunxi_nand_chip_init_timings(struct sunxi_nand_chip *chip,
>> +					struct device_node *np)
>> +{
>> +	const struct nand_sdr_timings *timings;
>> +	u32 min_clk_period = 0;
>> +	int ret;
>> +
>> +	ret = onfi_get_async_timing_mode(&chip->nand);
>> +	if (ret == ONFI_TIMING_MODE_UNKNOWN) {
>> +		ret = of_get_nand_onfi_timing_mode(np);
>> +		if (ret < 0)
>> +			return ret;
>> +	}
> [..]
>
>> +static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
> [..]
>> +       ret = sunxi_nand_chip_init_timings(chip, np);
>> +       if (ret)
>> +               return ret;
> [..]
>> +       ret = nand_scan_ident(mtd, nsels, NULL);
> This ordering looks a bit problematic, will onfi_get_async_timing_mode
> ever return anything other than ONFI_TIMING_MODE_UNKNOWN if it is
> called before nand_scan_ident ?
Indeed. I haven't tested this part as I don't own any board with an ONFI 
compatible chip.
> What sets clk_rate to non-zero if there
> is no DT property?
It is set to 20 MHz by default, but it should definitely be set to the 
rate fulfilling mode 0.
I'll fix this.

>
> For a flow that uses onfi_get_async_timing_mode rather than DT the
> driver should set the interface to timing mode 0 (slowest) and then
> call nand_scan_ident, and then reset the interface to the detected
> timing mode.

Absolutely.

>
> Maybe this should be implemented in the core code through a new
> callback (nand->set_timing_mode ?)
>
> Regards,
> Jason

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