Re: [RFC PATCH 1/2] PCI/ACPI: Add ACPI support for non ECAM Host Bridge Controllers

Lorenzo Pieralisi
2015-12-03T17:57:19Z

Hi Gab,

On Thu, Dec 03, 2015 at 11:19:58PM +0800, Gabriele Paoloni wrote:

[...]

> +void acpi_arm64_quirks(void)
> +{
> + int i = 0;
> +
> + while (quirks_array[i]) {
> + acpi_scan_add_handler(quirks_array[i]);
> + i++;
> + }
> +
> +}

This code is not arm64 specific, and this is part of a wider complaint
I have about this patchset and PCI/ACPI code I see in general.

> +
> +/*
> + * pci_ops specified by vendors that are not
> + * ECAM compliant
> + */
> +struct pci_ops *vendor_specific_ops;
> +
> +/* function to set vendor specific ops */
> +void set_quirk_pci_ops(struct pci_ops *quirk_ops)
> +{
> + vendor_specific_ops = quirk_ops;
> +}
> +
> +/* function to unset vendor specific ops */
> +void unset_quirk_pci_ops(void)
> +{
> + vendor_specific_ops = NULL;
> +}
> +
> /* Root bridge scanning */
> struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> {
> @@ -253,6 +291,9 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> return NULL;
> }
>
> + if (vendor_specific_ops)
> + acpi_pci_root_ops.pci_ops = vendor_specific_ops;

You are relying on the scan handlers calling ordering here, which as far
as I know depends on the ACPI tables layout, this is not acceptable,
we need to find a more robust implementation.

Let's first rewind a bit though, to summarize:

1) we need a way to configure a "generic host controller" with host
controller specific config methods (ie ECAM, even though is a PCI
standard it is not standard enough for some designers)
2) we keep the generic "PNP0A03" matching to declare a host bridge and
related resources (?). Maybe we can have an HID matching the
"real" device (eg "HISI0081" and related DSD) and a CID set to "PNP0A03" ?
I do not want to end up with two device objects in the ACPI tables.

I think that all this code belongs in:

drivers/pci/host/pci-host-generic.c

and the quirks scan should be done _within_ the pci_acpi_scan_root()
that should be placed in drivers/pci/host/pci-host-generic.c (ACPI probe
path, to be created) so that, if quirks for config space have to be applied
they are applied there before calling acpi_pci_root_create() so that
ordering is guaranteed.

I will put together a proposal to define the way we specify HID and
related DSD properties for PCI host controllers and send it to
the ACPI working group for review.

Second, I am against merging _any_ ACPI/PCI code for arm64 before we
define a way for the kernel to detect if resources should be reassigned
or just claimed as they are, as set-up by BIOS.

The current approach, that relies on initcalls (and that's horrible) and
that reassigns everything by default has to be overhauled to match
what x86 does, which is sensible to me (tries to claim, and for
resources that fail, it reassigns).

I will give this more thought and send a proposal to the ACPI working
group for review, so that we make this part of the specs before any
PCI/ACPI code for ARM64 gets close to the mainline kernel.

Comments welcome.

Thanks,
Lorenzo

> +
> bus = acpi_pci_root_create(root, &acpi_pci_root_ops, info, root);
>
> /* After the PCI-E bus has been walked and all devices discovered,
> diff --git a/arch/arm64/kernel/pci_quirks.h b/arch/arm64/kernel/pci_quirks.h
> new file mode 100644
> index 0000000..27055ff
> --- /dev/null
> +++ b/arch/arm64/kernel/pci_quirks.h
> @@ -0,0 +1,24 @@
> +/*
> + * PCIe host controller declarations for ACPI quirks
> + *
> + * Copyright (C) 2015 HiSilicon Co., Ltd. http://www.hisilicon.com
> + *
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef PCI_QUIRKS_H
> +#define PCI_QUIRKS_H
> +
> +/* declarations of vendor specific quirks */
> +extern struct acpi_scan_handler pci_root_hisi_handler;
> +
> +/* function to set vendor specific ops */
> +void set_quirk_pci_ops(struct pci_ops *quirk_ops);
> +
> +/* function to unset vendor specific ops */
> +void unset_quirk_pci_ops(void);
> +
> +#endif /*PCI_QUIRKS_H*/
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index e682dc6..ff362bb3d 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -863,5 +863,9 @@ void __init acpi_pci_root_init(void)
> return;
>
> pci_acpi_crs_quirks();
> +
> + /* Call quirks for non ECAM ARM64 Host Brdge controllers */
> + acpi_arm64_quirks();
> +
> acpi_scan_add_handler_with_hotplug(&pci_root_handler, "pci_root");
> }
> diff --git a/include/acpi/acpi_drivers.h b/include/acpi/acpi_drivers.h
> index 29c6912..17f4a37 100644
> --- a/include/acpi/acpi_drivers.h
> +++ b/include/acpi/acpi_drivers.h
> @@ -99,6 +99,12 @@ void pci_acpi_crs_quirks(void);
> static inline void pci_acpi_crs_quirks(void) { }
> #endif
>
> +#ifdef CONFIG_ARM64
> +void acpi_arm64_quirks(void);
> +#else
> +static inline void acpi_arm64_quirks(void) { }
> +#endif
> +
> /* --------------------------------------------------------------------------
> Processor
> -------------------------------------------------------------------------- */
> --
> 1.9.1
>