From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ezequiel Garcia <ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Subject: Re: [RFC PATCH v2 08/14] mtd: nand: add sunxi NAND
 flash controller support
Date: Wed, 29 Jan 2014 15:46:20 -0300
Message-ID: <20140129184619.GC27143@localhost>
References: <1391006064-28890-1-git-send-email-b.brezillon.dev@gmail.com>
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To: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: Boris BREZILLON <b.brezillon.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dev-3kdeTeqwOZ9EV1b7eY7vFQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Rob Landley <rob-VoJi6FS/r0vR7s880joybQ@public.gmane.org>, Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>, Brian Norris <computersforpeace-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
List-Id: devicetree@vger.kernel.org

On Wed, Jan 29, 2014 at 10:56:42AM -0700, Jason Gunthorpe wrote:
> On Wed, Jan 29, 2014 at 03:34:18PM +0100, Boris BREZILLON wrote:
>=20
> [..]
>=20
> > +static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *=
nfc,
> [..]
> > +       ret =3D sunxi_nand_chip_init_timings(chip, np);
> > +       if (ret)
> > +               return ret;
> [..]
> > +       ret =3D nand_scan_ident(mtd, nsels, NULL);
>=20
> 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 ? What sets clk_rate to non-zero if there
> is no DT property?
>=20
> 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.
>=20

Yes. And I believe this is a requirement from the ONFI 2.1 spec:

"""
4.1.4.3. Source Synchronous to Asynchronous
[..]

The host shall transition to the asynchronous data interface. Then the
host shall issue the Reset (FFh) command described in the previous paragrap=
h
using asynchronous timing mode 0, thus the host transitions to the asynchro=
nous
data interface prior to issuing the Reset (FFh). A device in any timing mod=
e is
required to recognize a Reset (FFh) command issued in asynchronous timing
mode 0.

[..]

After CE# has been pulled high and then transitioned low again, the host
should issue a Set Features to select the appropriate asynchronous timing m=
ode.
"""

--=20
Ezequiel Garc=C3=ADa, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com

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