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Date: Thu, 25 Sep 2014 09:06:01 +0200
From: Thierry Reding <thierry.reding@gmail.com>
To: Yijing Wang <wangyijing@huawei.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org, Xinwei Hu <huxinwei@huawei.com>,
	Wuyun <wuyun.wu@huawei.com>,
	linux-arm-kernel@lists.infradead.org,
	Russell King <linux@arm.linux.org.uk>,
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	Bharat.Bhushan@freescale.com, x86@kernel.org,
	Arnd Bergmann <arnd@arndb.de>,
	Thomas Gleixner <tglx@linutronix.de>,
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	Sebastian Ott <sebott@linux.vnet.ibm.com>,
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	"David S. Miller" <davem@davemloft.net>,
	sparclinux@vger.kernel.org, Chris Metcalf <cmetcalf@tilera.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	Lucas Stach <l.stach@pengutronix.de>,
	David Vrabel <david.vrabel@citrix.com>,
	Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Subject: Re: [PATCH v2 02/22] PCI/MSI: Remove useless bus->msi assignment
Message-ID: <20140925070601.GF12423@ulmo>
References: <1411614872-4009-1-git-send-email-wangyijing@huawei.com>
 <1411614872-4009-3-git-send-email-wangyijing@huawei.com>
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On Thu, Sep 25, 2014 at 11:14:12AM +0800, Yijing Wang wrote:
> Currently, PCI drivers will initialize bus->msi in
> pcibios_add_bus(). pcibios_add_bus() will be called
> in every pci bus initialization. So the bus->msi
> assignment in pci_alloc_child_bus() is useless.

I think this should be the other way around. The default should be to
inherit bus->msi from the parent. That way drivers don't typically have
to do it, yet they can still opt to override it if they need to.

For Tegra for example I think it would work if we assigned the MSI chip
to the root bus (in tegra_pcie_scan_bus()) and then have it propagated
to child busses in pci_alloc_child_bus() so that tegra_pcie_add_bus()
can be removed altogether.

Thierry

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