linux-kernel - Re: [PATCH 2/3] of: MSI: Simplify irqdomain lookup

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Date:	Tue, 26 Jan 2016 16:33:38 +0100
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh+dt@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/3] of: MSI: Simplify irqdomain lookup

Dear Marc Zyngier,

On Tue, 26 Jan 2016 13:52:26 +0000, Marc Zyngier wrote:
> So far, when trying to associate a device with its MSI domain,
> we first lookup the domain using a MSI token, and if this
> doesn't return anything useful, we pick up any domain matching
> the same node.
> 
> This logic is broken for two reasons:
> 1) Only the generic MSI code (PCI or platform) sets this token
>    to PCI/MSI or platform MSI. So we're guaranteed that if there
>    is something to be found, we will find it with the first call.
> 2) If we have a convoluted situation where:
>    - a single node implements both wired and MSI interrupts
>    - MSI support for that HW hasn't been compiled in
>    we'll end up using the wired domain for MSIs anyway, and things
>    break badly.
> 
> So let's just remove __of_get_msi_domain, and replace it by a direct
> call to irq_find_matching_host, because that's what we really want.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Tested-by: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>

(same testing as for PATCH 1/3)

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com