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

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Message-ID: <10db598eed716d7759bc0125b6977cf1@codeaurora.org>
Date:   Wed, 28 Oct 2020 23:54:23 +0530
From:   mdalam@...eaurora.org
To:     Miquel Raynal <miquel.raynal@...tlin.com>
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

On 2020-10-28 15:18, Miquel Raynal wrote:
> 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.
> 

I am agree with you, we should not add SPI-NAND changes inside
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.
> 

Initially I was started writing separate driver under SPI-NAND subsystem 
then I
realized that more than 85% of raw/qcom_nand.c code getting duplicated.

That's why I have added this SPI-NAND change in raw/qcom_nand.c since
more than 85% of code will be reused.

If I will add this change inside SPI-NAND subsystem then much of
raw/qcom_nand.c code will get duplicated. Would it be ok ?

> Thanks,
> Miquèl