linux-kernel - Re: [PATCH 6/8] PCI: host: brcmstb: add MSI capability

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Message-ID: <CANCKTBvAqu-godc03BiAt+9hxAoWABLVCtBzaA9ZWLJgXnQ3Fg@mail.gmail.com>
Date:   Wed, 25 Oct 2017 11:28:07 -0400
From:   Jim Quinlan <jim2101024@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>,
        linux-pci <linux-pci@...r.kernel.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        Kevin Cernekee <cernekee@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH 6/8] PCI: host: brcmstb: add MSI capability

On Tue, Oct 24, 2017 at 2:57 PM, Florian Fainelli <f.fainelli@...il.com> wrote:
> Hi Jim,
>
> On 10/24/2017 11:15 AM, Jim Quinlan wrote:
>> This commit adds MSI to the Broadcom STB PCIe host controller. It does
>> not add MSIX since that functionality is not in the HW.  The MSI
>> controller is physically located within the PCIe block, however, there
>> is no reason why the MSI controller could not be moved elsewhere in
>> the future.
>>
>> Since the internal Brcmstb MSI controller is intertwined with the PCIe
>> controller, it is not its own platform device but rather part of the
>> PCIe platform device.
>>
>> Signed-off-by: Jim Quinlan <jim2101024@...il.com>
>> ---
>>  drivers/pci/host/Kconfig           |  12 ++
>>  drivers/pci/host/Makefile          |   1 +
>>  drivers/pci/host/pci-brcmstb-msi.c | 318 +++++++++++++++++++++++++++++++++++++
>>  drivers/pci/host/pci-brcmstb.c     |  72 +++++++--
>>  drivers/pci/host/pci-brcmstb.h     |  26 +++
>>  5 files changed, 419 insertions(+), 10 deletions(-)
>>  create mode 100644 drivers/pci/host/pci-brcmstb-msi.c
>>
>> diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
>> index b9b4f11..54aa5d2 100644
>> --- a/drivers/pci/host/Kconfig
>> +++ b/drivers/pci/host/Kconfig
>> @@ -228,4 +228,16 @@ config PCI_BRCMSTB
>>       default ARCH_BRCMSTB || BMIPS_GENERIC
>>       help
>>         Adds support for Broadcom Settop Box PCIe host controller.
>> +       To compile this driver as a module, choose m here.
>> +
>> +config PCI_BRCMSTB_MSI
>> +     bool "Broadcom Brcmstb PCIe MSI support"
>> +     depends on ARCH_BRCMSTB || BMIPS_GENERIC
>
> This could probably be depends on PCI_BRCMSTB, which would imply these
> two conditions. PCI_BRCMSTB_MSI on its own is probably not very useful
> without the parent RC driver.
>
>> +     depends on OF
>> +     depends on PCI_MSI
>> +     default PCI_BRCMSTB
>> +     help
>> +       Say Y here if you want to enable MSI support for Broadcom's iProc
>> +       PCIe controller
>> +
>>  endmenu
>> diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
>> index c283321..1026d6f 100644
>> --- a/drivers/pci/host/Makefile
>> +++ b/drivers/pci/host/Makefile
>> @@ -23,6 +23,7 @@ obj-$(CONFIG_PCIE_TANGO_SMP8759) += pcie-tango.o
>>  obj-$(CONFIG_VMD) += vmd.o
>>  obj-$(CONFIG_PCI_BRCMSTB) += brcmstb-pci.o
>>  brcmstb-pci-objs := pci-brcmstb.o pci-brcmstb-dma.o
>> +obj-$(CONFIG_PCI_BRCMSTB_MSI) += pci-brcmstb-msi.o
>
> Should we combine this file with the brcmstb-pci.o? There is probably no
> functional difference, except that pci-brcmstb-msi.ko needs to be loaded
> first, right?
> --
> Florian

If you look at the pci/host/Kconfig you will see that other drivers
also have a separate MSI config (eg iproc, altera, xgene) so there is
precedent.  The reason that pci-brcmstb-msi.c is its own file is
because it depends on an irq function that is not exported.  That is
why CONFIG_PCI_BRCMSTB_MSI is bool, and CONFIG_PCI_BRCMSTB is
tristate.  -- Jim