linux-kernel - Re: [patch V2 34/46] PCI/MSI: Make arch_.*_msi

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Date:   Wed, 26 Aug 2020 22:14:58 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-hyperv@...r.kernel.org,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Jon Derrick <jonathan.derrick@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Wei Liu <wei.liu@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Steve Wahl <steve.wahl@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Russ Anderson <rja@....com>, linux-pci@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        xen-devel@...ts.xenproject.org, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Megha Dey <megha.dey@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Baolu Lu <baolu.lu@...el.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [patch V2 34/46] PCI/MSI: Make arch_.*_msi_irq[s] fallbacks selectable

On Wed, 26 Aug 2020 12:17:02 +0100,
Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> The arch_.*_msi_irq[s] fallbacks are compiled in whether an architecture
> requires them or not. Architectures which are fully utilizing hierarchical
> irq domains should never call into that code.
> 
> It's not only architectures which depend on that by implementing one or
> more of the weak functions, there is also a bunch of drivers which relies
> on the weak functions which invoke msi_controller::setup_irq[s] and
> msi_controller::teardown_irq.
> 
> Make the architectures and drivers which rely on them select them in Kconfig
> and if not selected replace them by stub functions which emit a warning and
> fail the PCI/MSI interrupt allocation.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V2: Make the architectures (and drivers) which need the fallbacks select them
>     and not the other way round (Bjorn).
> ---
>  arch/ia64/Kconfig              |    1 +
>  arch/mips/Kconfig              |    1 +
>  arch/powerpc/Kconfig           |    1 +
>  arch/s390/Kconfig              |    1 +
>  arch/sparc/Kconfig             |    1 +
>  arch/x86/Kconfig               |    1 +
>  drivers/pci/Kconfig            |    3 +++
>  drivers/pci/controller/Kconfig |    3 +++
>  drivers/pci/msi.c              |    3 ++-
>  include/linux/msi.h            |   31 ++++++++++++++++++++++++++-----
>  10 files changed, 40 insertions(+), 6 deletions(-)
> 

[...]

> --- a/drivers/pci/controller/Kconfig
> +++ b/drivers/pci/controller/Kconfig
> @@ -41,6 +41,7 @@ config PCI_TEGRA
>  	bool "NVIDIA Tegra PCIe controller"
>  	depends on ARCH_TEGRA || COMPILE_TEST
>  	depends on PCI_MSI_IRQ_DOMAIN
> +	select PCI_MSI_ARCH_FALLBACKS
>  	help
>  	  Say Y here if you want support for the PCIe host controller found
>  	  on NVIDIA Tegra SoCs.
> @@ -67,6 +68,7 @@ config PCIE_RCAR_HOST
>  	bool "Renesas R-Car PCIe host controller"
>  	depends on ARCH_RENESAS || COMPILE_TEST
>  	depends on PCI_MSI_IRQ_DOMAIN
> +	select PCI_MSI_ARCH_FALLBACKS
>  	help
>  	  Say Y here if you want PCIe controller support on R-Car SoCs in host
>  	  mode.
> @@ -103,6 +105,7 @@ config PCIE_XILINX_CPM
>  	bool "Xilinx Versal CPM host bridge support"
>  	depends on ARCH_ZYNQMP || COMPILE_TEST
>  	select PCI_HOST_COMMON
> +	select PCI_MSI_ARCH_FALLBACKS

This guy actually doesn't implement MSIs at all (it seems to delegate
them to an ITS present in the system, if I read the DT binding
correctly). However its older brother from the same silicon dealer
seems to need it. The patchlet below should fix it.

diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
index 9ad13919bcaa..f56ff049d469 100644
--- a/drivers/pci/controller/Kconfig
+++ b/drivers/pci/controller/Kconfig
@@ -96,6 +96,7 @@ config PCI_HOST_GENERIC
 
 config PCIE_XILINX
 	bool "Xilinx AXI PCIe host bridge support"
+	select PCI_MSI_ARCH_FALLBACKS
 	depends on OF || COMPILE_TEST
 	help
 	  Say 'Y' here if you want kernel to support the Xilinx AXI PCIe
@@ -105,7 +106,6 @@ config PCIE_XILINX_CPM
 	bool "Xilinx Versal CPM host bridge support"
 	depends on ARCH_ZYNQMP || COMPILE_TEST
 	select PCI_HOST_COMMON
-	select PCI_MSI_ARCH_FALLBACKS
 	help
 	  Say 'Y' here if you want kernel support for the
 	  Xilinx Versal CPM host bridge.


With that fixed,

Acked-by: Marc Zyngier <maz@...nel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.