linux-kernel - Re: [V8 1/2] irqchip: gic: Add support for multiple MSI for ARM64

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Date:	Mon, 22 Sep 2014 10:15:36 +0100
From:	Will Deacon <will.deacon@....com>
To:	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>
Cc:	Marc Zyngier <Marc.Zyngier@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	Pawel Moll <Pawel.Moll@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Harish.Kasiviswanathan@....com" <Harish.Kasiviswanathan@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [V8 1/2] irqchip: gic: Add support for multiple MSI for ARM64

Hi Suravee,

Just a few minor comments.

On Sat, Sep 20, 2014 at 05:31:37PM +0100, suravee.suthikulpanit@....com wrote:
> From: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> 
> This patch implelments the ARM64 version of arch_setup_msi_irqs(),
> which does not return 1 for when PCI_CAP_ID_MSI and nvec > 1.

s/implelments/implements/

> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> Acked-by: Marc Zyngier <Marc.Zyngier@....com>
> Cc: Mark Rutland <Mark.Rutland@....com>
> Cc: Jason Cooper <jason@...edaemon.net>
> Cc: Catalin Marinas <Catalin.Marinas@....com>
> Cc: Will Deacon <Will.Deacon@....com>
> ---
>  arch/arm64/kernel/Makefile |  1 +
>  arch/arm64/kernel/msi.c    | 41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 42 insertions(+)
>  create mode 100644 arch/arm64/kernel/msi.c
> 
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index df7ef87..a921c42 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -29,6 +29,7 @@ arm64-obj-$(CONFIG_ARM64_CPU_SUSPEND)	+= sleep.o suspend.o
>  arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
>  arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
>  arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
> +arm64-obj-$(CONFIG_PCI_MSI)		+= msi.o
>  
>  obj-y					+= $(arm64-obj-y) vdso/
>  obj-m					+= $(arm64-obj-m)
> diff --git a/arch/arm64/kernel/msi.c b/arch/arm64/kernel/msi.c
> new file mode 100644
> index 0000000..a295862
> --- /dev/null
> +++ b/arch/arm64/kernel/msi.c
> @@ -0,0 +1,41 @@
> +/*
> + * ARM64 architectural MSI implemention
> + *
> + * Support for Message Signalelled Interrupts for systems that
> + * implement ARM Generic Interrupt Controller: GICv2m.

You can drop the GICv2M reference here, as there's not really anything
GIC-specific in this file.

> + * Copyright (C) 2014 Advanced Micro Devices, Inc.
> + * Authors: Suravee Suthikulpanit <suravee.suthikulpanit@....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.
> + */
> +
> +#include <linux/irq.h>
> +#include <linux/msi.h>
> +#include <linux/pci.h>
> +
> +/*
> + * ARM64 function for seting up MSI irqs.
> + * Based on driver/pci/msi.c: arch_setup_msi_irqs().
> + *
> + * Note:
> + * Current implementation assumes that all interrupt controller used in
> + * ARM64 architecture _MUST_ supports multi-MSI.

I think you can remove this comment, to be honest.

> + */
> +int arm64_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> +{

Shouldn't this be called arch_setup_msi_irqs, since the intention is that
you override the weak symbol?

> +	struct msi_desc *entry;
> +	int ret;
> +
> +	list_for_each_entry(entry, &dev->msi_list, list) {
> +		ret = arch_setup_msi_irq(dev, entry);
> +		if (ret < 0)
> +			return ret;
> +		if (ret > 0)
> +			return -ENOSPC;

When does this function ever return a value > 0?

Will
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