linux-kernel - Re: [PATCH] PCI: set flag IRQCHIP_ONESHOT

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Date:   Sat, 4 Aug 2018 09:01:18 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Heiner Kallweit <hkallweit1@...il.com>
cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH] PCI: set flag IRQCHIP_ONESHOT_SAFE for PCI-MSI
 irqchip's

On Fri, 3 Aug 2018, Heiner Kallweit wrote:

> PCI-MSI is oneshot-safe, therefore set flag IRQCHIP_ONESHOT_SAFE to
> avoid unneeded masking/unmasking. See also discussion here:
> https://marc.info/?l=linux-pci&m=153332526101128&w=2

This changelog really wants a bit more detailed information.

> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/pci/msi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 4d88afdf..f2ef8964 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1446,6 +1446,9 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
>  	if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
>  		info->flags |= MSI_FLAG_MUST_REACTIVATE;
>  
> +	/* PCI-MSI is oneshot-safe */
> +	info->chip->flags |= IRQCHIP_ONESHOT_SAFE;
> +
>  	domain = msi_create_irq_domain(fwnode, info, parent);
>  	if (!domain)
>  		return NULL;
> -- 
> 2.18.0
> 
>