linux-kernel - Re: [PATCH 0/5] mtd: rawnand: qcom: Add support for QSPI nand

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Date:   Wed, 28 Oct 2020 10:48:35 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Md Sadre Alam <mdalam@...eaurora.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, 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 0/5] mtd: rawnand: qcom: Add support for QSPI nand

Hello,

Md Sadre Alam <mdalam@...eaurora.org> wrote on Sat, 10 Oct 2020
11:01:37 +0530:

> QPIC 2.0 supports Serial NAND support in addition to all features and
> commands in QPIC 1.0 for parallel NAND. Parallel and Serial NAND cannot
> operate simultaneously. QSPI nand devices will connect to QPIC IO_MACRO
> block of QPIC controller. There is a separate IO_MACRO clock for IO_MACRO
> block. Default IO_MACRO block divide the input clock by 4. so if IO_MACRO
> input clock is 320MHz then on bus it will be 80MHz, so QSPI nand device
> should also support this frequency.
> 
> QPIC provides 4 data pins to QSPI nand. In standard SPI mode (x1 mode) data
> transfer will occur on only 2 pins one pin for Serial data in and one for
> serial data out. In QUAD SPI mode (x4 mode) data transfer will occur at all
> the four data lines. QPIC controller supports command for x1 mode and x4 mode.
> 
> Md Sadre Alam (5):
>   dt-bindings: qcom_nandc: IPQ5018 QPIC NAND documentation
>   mtd: rawnand: qcom: Add initial support for qspi nand
>   mtd: rawnand: qcom: Read QPIC version
>   mtd: rawnand: qcom: Enable support for erase,read & write for serial
>     nand.
>   mtd: rawnand: qcom: Add support for serial training.
> 
>  .../devicetree/bindings/mtd/qcom_nandc.txt         |   3 +
>  drivers/mtd/nand/raw/nand_ids.c                    |  13 +
>  drivers/mtd/nand/raw/qcom_nandc.c                  | 502 ++++++++++++++++++++-
>  3 files changed, 494 insertions(+), 24 deletions(-)
> 

I'm sorry but this series clearly breaks the current layering. I cannot
authorize SPI-NAND code to fall into the raw NAND subsystem.

As both typologies cannot be used at the same time, I guess you should
have another driver handling this feature under the spi/ subsystem +
a few declarations in the SPI-NAND devices list.

Thanks,
Miquèl