Re: [PATCH V7 02/15] PCI: Disable MSI for Tegra194 root port

From: Vidya Sagar <vidyas@nvidia.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
	lorenzo.pieralisi@arm.com, mperttunen@nvidia.com,
	mmaddireddy@nvidia.com, linux-pci@vger.kernel.org,
	catalin.marinas@arm.com, will.deacon@arm.com,
	linux-kernel@vger.kernel.org, kthota@nvidia.com, kishon@ti.com,
	linux-tegra@vger.kernel.org, robh+dt@kernel.org,
	gustavo.pimentel@synopsys.com, jingoohan1@gmail.com,
	bhelgaas@google.com, jonathanh@nvidia.com,
	linux-arm-kernel@lists.infradead.org, sagar.tv@gmail.com
Subject: Re: [PATCH V7 02/15] PCI: Disable MSI for Tegra194 root port
Date: Wed, 22 May 2019 01:04:58 +0530	[thread overview]
Message-ID: <220fcb99-c3b5-58dc-a37a-57cbe9efa072@nvidia.com> (raw)
In-Reply-To: <f63051b0-a220-125b-219e-25156d65ea6d@nvidia.com>

On 5/21/2019 10:17 PM, 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.
>>>
>>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>>> ---
>>> 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 <treding@nvidia.com>
>>
> Ok. I'll move it to DWC driver along with name change for the quirk API.
> 
I see that if quirk macros and API are present in pcie-tegra194.c file and driver is built
as a module, quirk API is not getting invoked by the system, whereas it gets invoked if driver
is built into kernel. Is this behavior expected? I think it is because of quirk API symbol
not available as part of global quirk symbol table when driver is built as a module?
for now, I'm going to keep quirk macros and API in pci/quirks.c file itself.

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