linux-kernel - Re: [PATCH v2 1/8] PCI: rcar-gen2: Add support for clocks

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Date:   Thu, 14 Apr 2022 13:48:22 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Marek Vasut <marek.vasut+renesas@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Clement Leger <clement.leger@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: [PATCH v2 1/8] PCI: rcar-gen2: Add support for clocks

Hi Hervé,

On Thu, Apr 14, 2022 at 1:29 PM Herve Codina <herve.codina@...tlin.com> wrote:
> On Thu, 14 Apr 2022 10:45:54 +0200
> Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Thu, Apr 14, 2022 at 9:40 AM Herve Codina <herve.codina@...tlin.com> wrote:
> > > The PCI rcar-gen2 does not call any clk_prepare_enable().
> >
> > Correct, this driver manages the clocks indirectly through Runtime PM.
> >
> > > This lead to an access failure when the driver tries to access
> > > the IP (at least on a RZ/N1D platform).
> >
> > I expect adding
> >
> >     power-domans = <&sysctrl>;
> >
> > to the pci_usb node makes this patch redundant.
>
> Seems not enough.
> I tried what you suggest :
>  - Added 'power-domains = <&systrl>;' to the pci_usb node
>  - Added missing '#power-domain-cells = <0>;' to sysctrl node
>  - Reverted my patch.
>
> The system crashed at boot:

> [    0.832958] Unhandled fault: external abort on non-linefetch (0x1008) at 0x90b5f848

That's indeed a typical symptom of accessing a module's registers
while the module's clock is disabled.

> I also added a trace printk in r9a06g032-clocks.c and
> r9a06g032_attach_dev() was never called.
>
> Did I miss to set something ?

Do you have CONFIG_PM and CONFIG_PM_GENERIC_DOMAINS
enabled?
Apparently ARCH_RZN1 does not select these options yet.

Gr{oetje,eeting}s,

                        Geert

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