[PATCH 0/4] Add a property to override the quad mode

[Hsin-Yi Wang]

On Tue, Aug 15, 2023 at 11:59 PM Michael Walle <michael at walle.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
>