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

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Miquel,

On Thu, Sep 14, 2023 at 11:12 AM Miquel Raynal
<miquel.raynal@bootlin.com> wrote:
> geert@linux-m68k.org wrote on Thu, 14 Sep 2023 11:04:01 +0200:
> > On Thu, Sep 14, 2023 at 10:59 AM Miquel Raynal
> > <miquel.raynal@bootlin.com> wrote:
> > > geert@linux-m68k.org wrote on Thu, 14 Sep 2023 10:34:50 +0200:
> > > > On Thu, Sep 14, 2023 at 10:08 AM Krzysztof Kozlowski
> > > > <krzysztof.kozlowski@linaro.org> 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].
> > >
> > > Just FYI, I sent [2] after an unsuccessful attempt to update that list
> > > too, see [3]. The idea is: if you don't have anything useful to add,
> >
> > Oh, I didn't know that.
> >
> > > just use the generic compatible. If you need specific changes, you can
> > > add an entry.
> >
> > The problem is that usually these things are discovered too late,
> > so the only prudent way is to be proactive, and always add them.
> > Initially I thought that the different handling on RZ/G2L was due
> > to a difference in the RPC-IF block.  But now we know it's due to the
> > type of FLASH attached.
>
> Actually what I say is wrong, we are not supposed to touch that list
> anymore and prefer to handle the issues in the drivers by
> auto-discovery. Can't we do that in your case?

I'm not sure we can do that, as this code is part of the hardware
initialization during probing.
Biju: is this needed that early, or can it be done later, after the connected
device has been identified?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds