From: Boris Brezillon <boris.brezillon@collabora.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Mason Yang <masonccyang@mxic.com.tw>, Vignesh R <vigneshr@ti.com>,
Tudor Ambarus <Tudor.Ambarus@microchip.com>,
Julien Su <juliensu@mxic.com.tw>,
Richard Weinberger <richard@nod.at>,
Schrempf Frieder <frieder.schrempf@kontron.de>,
Marek Vasut <marek.vasut@gmail.com>,
linux-mtd@lists.infradead.org,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Brian Norris <computersforpeace@gmail.com>,
David Woodhouse <dwmw2@infradead.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 25/27] mtd: nand: Add helpers to manage ECC engines and configurations
Date: Mon, 25 Feb 2019 17:34:22 +0100 [thread overview]
Message-ID: <20190225173414.1836f0a8@kernel.org> (raw)
In-Reply-To: <20190225170118.62739fc4@xps13>
On Mon, 25 Feb 2019 17:01:18 +0100
Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> Hi Boris,
>
> Boris Brezillon <bbrezillon@kernel.org> wrote on Fri, 22 Feb 2019
> 15:44:31 +0100:
>
> > On Thu, 21 Feb 2019 13:58:04 +0100
> > Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> >
> > > Add the logic in the NAND core to find the right ECC engine depending
> > > on the NAND chip requirements and the user desires. Right now, the
> > > choice may be made between (more will come):
> > > * software Hamming
> > > * software BCH
> > > * on-die (SPI-NAND devices only)
> > >
> > > Once the ECC engine has been found, the ECC engine must be
> > > configured.
> > >
> > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > ---
> > > drivers/mtd/nand/core.c | 107 +++++++++++++++++++++++++++++++++++++++
> > > include/linux/mtd/nand.h | 4 ++
> > > 2 files changed, 111 insertions(+)
> > >
> > > diff --git a/drivers/mtd/nand/core.c b/drivers/mtd/nand/core.c
> > > index 872d46b5fc0f..9feb118c9f68 100644
> > > --- a/drivers/mtd/nand/core.c
> > > +++ b/drivers/mtd/nand/core.c
> > > @@ -207,6 +207,113 @@ int nanddev_mtd_max_bad_blocks(struct mtd_info *mtd, loff_t offs, size_t len)
> > > }
> > > EXPORT_SYMBOL_GPL(nanddev_mtd_max_bad_blocks);
> > >
> > > +/**
> > > + * nanddev_find_ecc_engine() - Find a suitable ECC engine
> > > + * @nand: NAND device
> > > + */
> > > +static int nanddev_find_ecc_engine(struct nand_device *nand)
> >
> > Can we pass the conf in argument instead of reading it from
> > nand->ecc.user_conf?
> >
> > > +{
> > > + bool is_spinand = mtd_type_is_spinand(&nand->mtd);
> >
> > And here is the reason for the SPINAND type.
> >
> > > +
> > > + /* Read the user desires in terms of ECC engine/configuration */
> > > + nand_ecc_read_user_conf(nand);
> > > +
> > > + /* No ECC engine requestedn, let's return without error */
> > > + if (nand->ecc.user_conf.mode == NAND_ECC_NONE)
> > > + return 0;
> > > +
> > > + /* Raw NAND default mode is hardware */
> > > + if (!is_spinand && nand->ecc.user_conf.mode < 0)
> > > + nand->ecc.user_conf.mode = NAND_ECC_HW;
> >
> > We should let the raw NAND layer take this decision (actually, it's
> > even a raw NAND controller driver decision). Please complain if
> > user_conf.mode is invalid.
> > This way you won't need the SPINAND type you added in one of your
> > previous patch.
> >
> > > +
> > > + /* SPI-NAND default mode is on-die */
> > > + if (is_spinand && nand->ecc.user_conf.mode < 0)
> > > + nand->ecc.user_conf.mode = NAND_ECC_ON_DIE;
> > > +
> > > + switch (nand->ecc.user_conf.mode) {
> > > + case NAND_ECC_SOFT:
> > > + nand->ecc.engine = nand_ecc_sw_get_engine(nand);
> > > + break;
> > > + case NAND_ECC_ON_DIE:
> > > + if (is_spinand)
> > > + nand->ecc.engine = spinand_ondie_ecc_get_engine();
> >
> > So, maybe it's worth having the ondie ECC engine instance directly
> > embedded in nand_device instead of spinand, or maybe just a pointer, so
> > that you don't reserve extra space when the NAND device does not have
> > on-die ECC.
> >
> > > + else
> > > + pr_err("On-die ECC engines for non SPI devices not supported yet\n");
> > > + break;
> > > + case NAND_ECC_HW:
> > > + pr_err("Hardware ECC engines not supported yet\n");
> > > + break;
> > > + default:
> > > + pr_err("Missing ECC engine property\n");
> > > + }
> > > +
> > > + if (!nand->ecc.engine)
> > > + return -EINVAL;
> > > +
> > > + return 0;
> > > +}
> >
>
> I think this is the root patch were our ideas diverge. For me, each
> 'ECC engine' has a _get() helper and the NAND core decides which one to
> call to retrieve the right engine. Can you please explain what was your
> idea if this one does not fit?
Each class of ECC engine has its own way of getting a pointer to an ECC
engine instance:
- ondie: the engine is directly attached to the device and can be
retrieved by accessing a nand_device field (nanddev->ondie_ecc?).
- sw ECC: you can create a new instance for each device and possibly
pass the OOB layout you want to use (assuming you don't want to use
the default one)
- HW-controller-side engine: refers to the controller device (parent
node) or the device pointed by the ecc-engine DT prop (we'll probably
need a way to pass this info when for non-DT platforms). For this one
we'll add a nanddev_get_hw_ecc_engine() which will search for all
registered HW ECC engines and try to match with some search keys (in
case of DT, it's the ->of_node pointer address)
Clearly, for SW-based ECC, you'll need more than just the nanddev
object, as layouts can differ depending on the controller driver. So,
what I'm suggesting is to have a
nand_create_sw_ecc_engine(algo, layout)
funtion that returns this ECC engine instance which the driver will
then attach to the NAND device.
>
> Also, the parsing of the DT (in nand_ecc_read_user_conf()) gives me the
> user ECC mode and algo, so I cannot let the raw NAND core (or a raw
> NAND controller driver) or the SPI NAND core decide which mode is the
> default if not provided by the user.
Except this prop is optional in most cases, and the default value is
not always the same, which is why I think this ECC engine retrieval step
should be left to each sub-layer (and sometimes to the controller driver
behind it). Maybe you can provide helpers to help with that, but I
don't think taking this decision here, based on the bus type, is a good
idea. And I also don't like the idea of adding a new SPINAND type.
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next prev parent reply other threads:[~2019-02-25 16:34 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 12:57 [RFC PATCH 13/27] mtd: nand: ecc: Clarify the software Hamming introductory line Miquel Raynal
2019-02-21 12:57 ` [RFC PATCH 14/27] mtd: nand: ecc: Turn the software Hamming implementation generic Miquel Raynal
2019-02-21 13:22 ` Boris Brezillon
2019-02-21 12:57 ` [RFC PATCH 15/27] mtd: nand: Remove useless include about software Hamming ECC Miquel Raynal
2019-02-21 12:57 ` [RFC PATCH 16/27] mtd: nand: ecc: Let the software BCH ECC engine be a module Miquel Raynal
2019-02-21 13:48 ` Adam Ford
2019-02-21 14:02 ` Miquel Raynal
2019-02-22 14:24 ` Boris Brezillon
2019-02-21 12:57 ` [RFC PATCH 17/27] mtd: nand: ecc: Let the software Hamming ECC engine be unselected Miquel Raynal
2019-02-21 13:20 ` Boris Brezillon
2019-02-21 13:35 ` Miquel Raynal
2019-02-21 13:41 ` Boris Brezillon
2019-02-21 13:46 ` Miquel Raynal
2019-02-21 12:57 ` [RFC PATCH 18/27] mtd: nand: ecc: Create the software BCH engine instance Miquel Raynal
2019-02-21 12:57 ` [RFC PATCH 19/27] mtd: nand: ecc: Create the software Hamming " Miquel Raynal
2019-02-21 12:57 ` [RFC PATCH 20/27] mtd: nand: Let software ECC engines be retrieved from the NAND core Miquel Raynal
2019-02-22 14:29 ` Boris Brezillon
2019-02-25 15:49 ` Miquel Raynal
2019-02-25 16:13 ` Boris Brezillon
2019-02-26 15:54 ` Miquel Raynal
2019-02-21 12:58 ` [RFC PATCH 21/27] mtd: spinand: Fix typo in comment Miquel Raynal
2019-02-22 14:31 ` Boris Brezillon
2019-02-21 12:58 ` [RFC PATCH 22/27] mtd: spinand: Let the SPI-NAND core flag a SPI-NAND chip Miquel Raynal
2019-02-22 14:33 ` Boris Brezillon
2019-02-21 12:58 ` [RFC PATCH 23/27] mtd: spinand: Move the ECC helper functions into a separate file Miquel Raynal
2019-02-21 12:58 ` [RFC PATCH 24/27] mtd: spinand: Instantiate a SPI-NAND on-die ECC engine Miquel Raynal
2019-02-22 14:38 ` Boris Brezillon
2019-02-21 12:58 ` [RFC PATCH 25/27] mtd: nand: Add helpers to manage ECC engines and configurations Miquel Raynal
2019-02-22 14:44 ` Boris Brezillon
2019-02-25 16:01 ` Miquel Raynal
2019-02-25 16:34 ` Boris Brezillon [this message]
2019-02-25 18:48 ` Boris Brezillon
2019-02-26 15:59 ` [RFC PATCH 25/27] mtd: nand: Add helpers to manage ECC engines and configurationsND Miquel Raynal
2019-02-26 16:04 ` Boris Brezillon
2019-02-27 14:07 ` [RFC PATCH 25/27] mtd: nand: Add helpers to manage ECC engines and configurations Miquel Raynal
2019-02-27 14:30 ` Boris Brezillon
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