linux-kernel - Re: [PATCH 0/4] Add a property to override the quad mode

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Date:   Wed, 16 Aug 2023 01:21:40 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Michael Walle <michael@...le.cc>
Cc:     Tudor Ambarus <tudor.ambarus@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Pratyush Yadav <pratyush@...nel.org>,
        "Miquel Raynal )" <miquel.raynal@...tlin.com>,
        "Richard Weinberger )" <richard@....at>,
        "Vignesh Raghavendra )" <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        cros-qcom-dts-watchers@...omium.org,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: Re: [PATCH 0/4] Add a property to override the quad mode

On Tue, Aug 15, 2023 at 11:59 PM Michael Walle <michael@...le.cc> wrote:
>
> Hi,
>
> >On gigadevice gd25lq64c, the quad mode is enabled after BFPT is parsed.
> >According to datasheet[1], Quad enable (QE) bit needs to be set to 0 to
> >use write protection (WP) pin. It also recommends setting default value of
> >QE to 0 to avoid a potential short issue.
>
> So you are using either dual or single io mode. Why can't you use the device tree property spi-{tx,rx}-bus-width?

I tried setting spi-tx-bus-width and spi-rx-bus-width to either 0 or 1
and WP still doesn't work.
For this chip, quad_enable will be set to spi_nor_sr2_bit1_quad_enable
(QER flag is BFPT_DWORD15_QER_SR2_BIT1_BUGGY)[1]

spi_nor_write_sr_and_check() calls
spi_nor_write_16bit_sr_and_check()[2] and the function sets QE bit if
quad_enable is not NULL.

[1] https://elixir.bootlin.com/linux/latest/source/drivers/mtd/spi-nor/sfdp.c#L575
[2] https://elixir.bootlin.com/linux/latest/source/drivers/mtd/spi-nor/core.c#L879

Setting spi-{tx,rx}-bus-width still falls to this function and cases.

>
> >Add a disable-quad-mode property in devicetree that platform can use it to
> >override the quad mode status parsed from BFPT to use write protection.
> >
> >[1]
> >https://www.elm-tech.com/ja/products/spi-flash-memory/gd25lq64/gd25lq64.pdf
>
> should be a link on the vendor Homepage if possible.

Right, https://www.gigadevice.com.cn/Public/Uploads/uploadfile/files/20220714/DS-00012-GD25LQ64C-Rev3.4.pdf
is a more proper datasheet source. The QE description is also in page
13.

>
> -michael
>