Re: [RESEND v5 09/21] mtd: rawnand: Create a new enumeration to describe properly ECC types

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, Vignesh Raghavendra <vigneshr@ti.com>,
	Tudor Ambarus <Tudor.Ambarus@microchip.com>,
	Richard Weinberger <richard@nod.at>,
	Rob Herring <robh+dt@kernel.org>,
	linux-mtd@lists.infradead.org
Subject: Re: [RESEND v5 09/21] mtd: rawnand: Create a new enumeration to describe properly ECC types
Date: Wed, 27 May 2020 10:33:56 +0200	[thread overview]
Message-ID: <20200527103356.56e145a9@xps13> (raw)
In-Reply-To: <20200527005928.39c549e2@collabora.com>

Boris Brezillon <boris.brezillon@collabora.com> wrote on Wed, 27 May
2020 00:59:28 +0200:

> On Tue, 26 May 2020 21:56:21 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > Now that the misleading mix between ECC engine type and OOB placement
> > has been addressed, add a new enumeration to properly define ECC types
> > (also called provider or mode).
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> > ---
> >  drivers/mtd/nand/raw/nand_base.c |  7 +++++++
> >  include/linux/mtd/rawnand.h      | 16 ++++++++++++++++
> >  2 files changed, 23 insertions(+)
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index 515cd4681660..5c6ab5b93270 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -5018,6 +5018,13 @@ static const char * const nand_ecc_modes[] = {
> >  	[NAND_ECC_ON_DIE]	= "on-die",
> >  };
> >  
> > +static const char * const nand_ecc_engine_providers[] = {  
> 
> This table is not used here, are you sure it should be introduced now?
> 
> > +	[NAND_ECC_ENGINE_NONE] = "none",
> > +	[NAND_ECC_ENGINE_SOFT] = "soft",
> > +	[NAND_ECC_ENGINE_CONTROLLER] = "hw",  
> 
> 					^ "on-controller" ?

This would break DT backward compatibility, I am afraid I cannot do
that. Honnestly, I find "hw" good enough because "on-controller" is
also too restrictive. What about an external (non-pipelined) engine
like the one I am about to introduce?

> 
> > +	[NAND_ECC_ENGINE_ON_DIE] = "on-die",
> > +};
> > +
> >  static const char * const nand_ecc_placement[] = {
> >  	[NAND_ECC_PLACEMENT_INTERLEAVED] = "interleaved",
> >  };
> > diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
> > index dc909fb977c7..a2078c5f3d21 100644
> > --- a/include/linux/mtd/rawnand.h
> > +++ b/include/linux/mtd/rawnand.h
> > @@ -92,6 +92,22 @@ enum nand_ecc_mode {
> >  	NAND_ECC_ON_DIE,
> >  };
> >  
> > +/**
> > + * enum nand_ecc_engine_type - NAND ECC engine type/provider
> > + * @NAND_ECC_ENGINE_INVALID: Invalid value
> > + * @NAND_ECC_ENGINE_NONE: No ECC correction
> > + * @NAND_ECC_ENGINE_SOFT: Software ECC correction
> > + * @NAND_ECC_ENGINE_CONTROLLER: Hardware controller ECC correction
> > + * @NAND_ECC_ENGINE_ON_DIE: On chip hardware ECC correction
> > + */
> > +enum nand_ecc_engine_type {
> > +	NAND_ECC_ENGINE_INVALID,
> > +	NAND_ECC_ENGINE_NONE,
> > +	NAND_ECC_ENGINE_SOFT,
> > +	NAND_ECC_ENGINE_CONTROLLER,
> > +	NAND_ECC_ENGINE_ON_DIE,
> > +};
> > +
> >  /**
> >   * enum nand_ecc_placement - NAND ECC placement
> >   * @NAND_ECC_PLACEMENT_FREE: The driver can decide where to put ECC bytes.  
> 

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