From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vidya Sagar Subject: Re: [PATCH V7 02/15] PCI: Disable MSI for Tegra194 root port Date: Wed, 22 May 2019 13:37:58 +0530 Message-ID: <4a9dadc5-7e16-4893-c7c2-acd7f515e039@nvidia.com> References: <20190517123846.3708-1-vidyas@nvidia.com> <20190517123846.3708-3-vidyas@nvidia.com> <20190521102729.GB29166@ulmo> <20190521193616.GE57618@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190521193616.GE57618@google.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Bjorn Helgaas Cc: Thierry Reding , lorenzo.pieralisi@arm.com, robh+dt@kernel.org, mark.rutland@arm.com, jonathanh@nvidia.com, kishon@ti.com, catalin.marinas@arm.com, will.deacon@arm.com, jingoohan1@gmail.com, gustavo.pimentel@synopsys.com, mperttunen@nvidia.com, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com List-Id: linux-tegra@vger.kernel.org On 5/22/2019 1:06 AM, Bjorn Helgaas wrote: > On Tue, May 21, 2019 at 10:17:26PM +0530, Vidya Sagar wrote: >> On 5/21/2019 3:57 PM, Thierry Reding wrote: >>> On Fri, May 17, 2019 at 06:08:33PM +0530, Vidya Sagar wrote: >>>> Tegra194 rootports don't generate MSI interrupts for PME events and hence >>>> MSI needs to be disabled for them to avoid root ports service drivers >>>> registering their respective ISRs with MSI interrupt. > > The service drivers (AER, hotplug, etc) don't know whether the > interrupt is INTx or MSI; they just register their ISRs with > pcie_device.irq. > > The point of this patch is that the PCI core doesn't support devices > that use MSI and INTx at the same time, and since this device can't > generate MSI for PME, we have to use INTx for *all* its interrupts. > >>>> Signed-off-by: Vidya Sagar >>>> --- >>>> Changes since [v6]: >>>> * This is a new patch >>>> >>>> drivers/pci/quirks.c | 14 ++++++++++++++ >>>> 1 file changed, 14 insertions(+) >>>> >>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c >>>> index 0f16acc323c6..28f9a0380df5 100644 >>>> --- a/drivers/pci/quirks.c >>>> +++ b/drivers/pci/quirks.c >>>> @@ -2592,6 +2592,20 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA, >>>> PCI_DEVICE_ID_NVIDIA_NVENET_15, >>>> nvenet_msi_disable); >>>> +/* >>>> + * Tegra194's PCIe root ports don't generate MSI interrupts for PME events >>>> + * instead legacy interrupts are generated. Hence, to avoid service drivers >>>> + * registering their respective ISRs for MSIs, need to disable MSI interrupts >>>> + * for root ports. >>>> + */ >>>> +static void disable_tegra194_rp_msi(struct pci_dev *dev) >>>> +{ >>>> + dev->no_msi = 1; >>>> +} >>>> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA, 0x1ad0, disable_tegra194_rp_msi); >>>> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA, 0x1ad1, disable_tegra194_rp_msi); >>>> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA, 0x1ad2, disable_tegra194_rp_msi); >>>> + >>> >>> Later functions in this file seem to use a more consistent naming >>> pattern, according to which the name for this would become: >>> >>> pci_quirk_nvidia_tegra194_disable_rp_msi >>> >>> Might be worth considering making this consistent. >>> >>> This could also be moved to the DWC driver to restrict this to where it >>> is needed. In either case, this seems like a good solution, so: >>> >>> Reviewed-by: Thierry Reding >>> >> Ok. I'll move it to DWC driver along with name change for the quirk API. > > Is there any possibility this hardware would be used in an ACPI > system? If so, the quirk should probably stay in drivers/pci/quirks.c > because the DWC driver would not be present. Yes. There is a plan to boot kernel through UEFI (using ACPI) on this system. So, I'll move it to drivers/pci/quirks.c file. > > Either way, please also add some PCIe spec references about this in > the changelog and a comment in the code about working around this > issue. I think the MSI/MSI-X sections that prohibit a device from > using both INTx and MSI/MSI-X are probably the most pertinent. Ok. I'll take care of it in the next patch series. > > The reason I want a comment about this is to discourage future > hardware from following this example because every device that *does* > follow this example requires a kernel update that would be otherwise > unnecessary. Ok. I'll take it up with our hardware engineers to have only MSI/MSI-X interrupts getting generated for all root port received events. > > Bjorn >