Re: [PATCH] memory: renesas-rpc-if: Fix IO state based on flash type

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Krzysztof,

CC Rob, Miquel

On Thu, Sep 14, 2023 at 10:08 AM Krzysztof Kozlowski
<krzysztof.kozlowski@xxxxxxxxxx> wrote:
> On 30/08/2023 17:18, Biju Das wrote:
> >>>                 regmap_update_bits(rpc->regmap, RPCIF_CMNCR, @@ -774,6
> >>> +776,12 @@ static int rpcif_probe(struct platform_device *pdev)
> >>>                 return ret;
> >>>         }
> >>>
> >>> +       if (rpc->info->type == RPCIF_RZ_G2L &&
> >>
> >> Wouldn't this apply to non-RZ/G2L systems, too?
> >
> > It applies, if the device uses the flash[1] or [2] and it needs
> > 4-bit tx support.
> >
> > [1] Figure 20: QUAD INPUT/OUTPUT FAST READ – EBh/ECh
> > https://media-www.micron.com/-/media/client/global/documents/products/data-sheet/nor-flash/serial-nor/mt25q/die-rev-a/mt25q_qlks_u_512_aba_0.pdf?rev=3e5b2a574f7b4790b6e58dacf4c889b2
> >
> > [2] section 8.14
> >
> > https://www.renesas.com/eu/en/document/dst/at25ql128a-datasheet?r=1608586
>
> Geert,
>
> Does it answer your comment or do you expect here some changes?

Well, now it has been confirmed this applies to non-RZ/G2L systems, too,
the check for RPCIF_RZ_G2L should probably be removed.  In upstream,
only arch/arm64/boot/dts/renesas/rzg2l{,c}-smarc-som.dtsi have devices
that are compatible with "micron,mt25qu512a", but obviously they can
appear elsewhere, too.

Now, the presence of that compatible value in rzg2l{,c}-smarc-som.dtsi
currently causes a dtbs_check warning, as it is not documented.
However, there has been some pushback against adding more compatible
values, cfr. my patch to add mt25qu512a[1], and Miquel's commit [2].
But the issue Biju is seeing proves there is a need to add these.

In addition, I had hoped to gather some feedback or guidance from the
hyperbus and/or spi people, as issues w.r.t. pin states will eventually
pop up on other systems, too, and thus may need handling in the core,
instead of in each individual device driver.  But of course that can
be done later, when the need arises.

Thanks!

[1] "[PATCH] dt-bindings: mtd: jedec,spi-nor: Document support for
more MT25QU parts"
    https://lore.kernel.org/all/363186079b4269891073f620e3e2353cf7d2559a.1669988238.git.geert+renesas@xxxxxxxxx
[2] 4b0cb4e7ab2f777c ("dt-bindings: mtd: spi-nor: clarify the need for
spi-nor compatibles").

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
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                                -- Linus Torvalds