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

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Date:   Wed, 16 Aug 2023 18:48:24 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Michael Walle <michael@...le.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 Wed, Aug 16, 2023 at 3:19 AM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 15/08/2023 19:21, Hsin-Yi Wang wrote:
> > 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.
>
> with tx/rx bus width = 2, how quad mode is still possible? IOW, why do
> you need new property? You wrote here about driver, but I ask about
> bindings.
>
This may be a bug in the driver that setting spi-{tx,rx}-bus-width
still enables the QE bit. I proposed another method in the chip's
fixup to deal with this issue instead of creating a new binding
property.
v2: https://lore.kernel.org/lkml/20230816104245.2676965-1-hsinyi@chromium.org/


> Best regards,
> Krzysztof
>