linux-kernel - Re: [PATCH 2/5] mtd: rawnand: qcom: Add initial support for qspi nand

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Message-ID: <20201029100751.713e27df@collabora.com>
Date:   Thu, 29 Oct 2020 10:07:51 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Md Sadre Alam <mdalam@...eaurora.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org,
        miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
        robh+dt@...nel.org, linux-arm-msm@...r.kernel.org,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, sricharan@...eaurora.org
Subject: Re: [PATCH 2/5] mtd: rawnand: qcom: Add initial support for qspi
 nand

Hello,

On Sat, 10 Oct 2020 11:01:39 +0530
Md Sadre Alam <mdalam@...eaurora.org> wrote:

> This change will add initial support for qspi (serial nand).
> 
> QPIC Version v.2.0 onwards supports serial nand as well so this
> change will initialize all required register to enable qspi (serial
> nand).
> 
> This change is supporting very basic functionality of qspi nand flash.
> 
> 1. Reset device (Reset QSPI NAND device).
> 
> 2. Device detection (Read id QSPI NAND device).

Unfortunately, that's not going to work in the long term. You're
basically hacking the raw NAND framework to make SPI NANDs fit. I do
understand the rationale behind this decision (re-using the code for
ECC and probably other things), but that's not going to work. So I'd
recommend doing the following instead:

1/ implement a SPI-mem controller driver
2/ implement an ECC engine driver so the ECC logic can be shared
   between the SPI controller and raw NAND controller drivers
3/ convert the raw NAND driver to the exec_op() interface (none of
   this hack would have been possible if the driver was using the new
   API)

Regards,

Boris