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Re: [Xen-devel] [PATCH v2 02/22] PCI/MSI: Remove useless bus->msi assignment
- To: Yijing Wang <wangyijing@xxxxxxxxxx>
- From: Thierry Reding <thierry.reding@xxxxxxxxx>
- Date: Thu, 25 Sep 2014 09:06:01 +0200
- Cc: linux-mips@xxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-pci@xxxxxxxxxxxxxxx, Bharat.Bhushan@xxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, Russell King <linux@xxxxxxxxxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, x86@xxxxxxxxxx, Sebastian Ott <sebott@xxxxxxxxxxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, arnab.basu@xxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, Chris Metcalf <cmetcalf@xxxxxxxxxx>, Bjorn Helgaas <bhelgaas@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>, Xinwei Hu <huxinwei@xxxxxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Ralf Baechle <ralf@xxxxxxxxxxxxxx>, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>, Wuyun <wuyun.wu@xxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, "David S. Miller" <davem@xxxxxxxxxxxxx>, Lucas Stach <l.stach@xxxxxxxxxxxxxx>
- Delivery-date: Thu, 25 Sep 2014 07:12:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
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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