linux-kernel - Re: [RFC PATCH 2/2] asm-generic: Add new pci.h and use it

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Message-ID: <CAK8P3a2_HKMf8nMcSkK1_jyCEHEdzz=YiRmPvN+ACbPTafXJzA@mail.gmail.com>
Date:   Fri, 15 Jul 2022 10:09:21 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Stafford Horne <shorne@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-um <linux-um@...ts.infradead.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [RFC PATCH 2/2] asm-generic: Add new pci.h and use it

On Thu, Jul 14, 2022 at 11:46 PM Stafford Horne <shorne@...il.com> wrote:
>
> The asm/pci.h used for many newer architectures share similar
> definitions.  Move the common parts to asm-generic/pci.h to allow for
> sharing code.

This looks very nice, thanks for doing it!

> Two things to note are:
>
>  - isa_dma_bridge_buggy, traditionally this is defined in asm/dma.h but
>    these architectures avoid creating that file and add the definition
>    to asm/pci.h.

I would prefer if we could just kill off this variable for non-x86, as it's
only set to a nonzero value in two implementations that are both
x86-specific and most of the references are gone. That does not have
to be part of this series though, if you don't want to address it here, just
add a comment to the new pci.h file.

>  - ARCH_GENERIC_PCI_MMAP_RESOURCE, csky does not define this so we
>    undefine it after including asm-generic/pci.h.  Why doesn't csky
>    define it?

Adding David Woodhouse to Cc, as he introduced this interface. As I
understand it, this was meant as a replacement for the old
architecture specific pci_mmap_page_range interface, and is ideally
used everywhere.

It's probably something that slipped through the review of csky and
should have been there.

As an aside, it seems the pci_mmap_page_range() cleanup was
left almost complete, with sparc being the only one left after
David Miller found a problem with the generic code. Not sure if
this was ever resolved:
https://lore.kernel.org/lkml/1519887203.622.3.camel@infradead.org/t/#u

> +#ifndef PCIBIOS_MIN_IO
> +#define PCIBIOS_MIN_IO         0
> +#endif
> +
> +#define PCIBIOS_MIN_MEM                0

We should probably #ifdef both of these for consistency.

> +static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
> +{
> +       /* no legacy ide irq support */
> +       return -ENODEV;
> +}

And this can just go away now, according to what we found.

        Arnd