linux-kernel - Re: [PATCH V5 5/5] PCI: tegra: Add support for PCIe endpoint mode in Tegra194

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Message-ID: <bba72560-85cc-b59b-b0e8-bfc7c7408736@nvidia.com>
Date:   Tue, 31 Mar 2020 08:25:08 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     Bjorn Helgaas <helgaas@...nel.org>, <lorenzo.pieralisi@....com>
CC:     <robh+dt@...nel.org>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <andrew.murray@....com>, <kishon@...com>,
        <gustavo.pimentel@...opsys.com>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <sagar.tv@...il.com>
Subject: Re: [PATCH V5 5/5] PCI: tegra: Add support for PCIe endpoint mode in
 Tegra194



On 3/31/2020 3:17 AM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Tue, Mar 03, 2020 at 11:40:52PM +0530, Vidya Sagar wrote:
>> Add support for the endpoint mode of Synopsys DesignWare core based
>> dual mode PCIe controllers present in Tegra194 SoC.
>>
>> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
>> Acked-by: Thierry Reding <treding@...dia.com>
>> ---
>> V5:
>> * Added Acked-by: Thierry Reding <treding@...dia.com>
>> * Removed unwanted header file inclusion
>>
>> V4:
>> * Addressed Lorenzo's review comments
>> * Started using threaded irqs instead of kthreads
>>
>> V3:
>> * Addressed Thierry's review comments
>>
>> V2:
>> * Addressed Bjorn's review comments
>> * Made changes as part of addressing review comments for other patches
>>
>>   drivers/pci/controller/dwc/Kconfig         |  30 +-
>>   drivers/pci/controller/dwc/pcie-tegra194.c | 679 ++++++++++++++++++++-
>>   2 files changed, 691 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
>> index 0830dfcfa43a..169cde58dd92 100644
>> --- a/drivers/pci/controller/dwc/Kconfig
>> +++ b/drivers/pci/controller/dwc/Kconfig
>> @@ -248,14 +248,38 @@ config PCI_MESON
>>          implement the driver.
>>
>>   config PCIE_TEGRA194
>> -     tristate "NVIDIA Tegra194 (and later) PCIe controller"
>> +     tristate
>> +
>> +config PCIE_TEGRA194_HOST
>> +     tristate "NVIDIA Tegra194 (and later) PCIe controller - Host Mode"
>>        depends on ARCH_TEGRA_194_SOC || COMPILE_TEST
>>        depends on PCI_MSI_IRQ_DOMAIN
>>        select PCIE_DW_HOST
>>        select PHY_TEGRA194_P2U
>> +     select PCIE_TEGRA194
>> +     default y
> 
> Sorry I missed this before, but why is this "default y"?  From
> Documentation/kbuild/kconfig-language.rst:
> 
>    The default value deliberately defaults to 'n' in order to avoid
>    bloating the build. With few exceptions, new config options should
>    not change this. The intent is for "make oldconfig" to add as little
>    as possible to the config from release to release.
> 
> I do see that several other things in other drivers/pci/ Kconfig files
> are also "default y", and we should probably change some of them.  But
> I don't want to add even more unless there's a good reason.
> 
> I'm not looking for more reactions like these:
> 
> https://lore.kernel.org/r/CAHk-=wiZ24JuVehJ5sEC0UG1Gk2nvB363wO02RRsR1oEht6R9Q@mail.gmail.com
> https://lore.kernel.org/r/CA+55aFzPpuHU1Nqd595SEQS=F+kXMzPs0Rba9FUgTodGxmXsgg@mail.gmail.com
> 
> Can you please update this patch to either remove the "default y" or
> add the rationale for keeping it?
I'm fine with removing 'default y' line.
Should I send a patch only with this change?

Thanks,
Vidya Sagar
> 
>> +     help
>> +       Enables support for the PCIe controller in the NVIDIA Tegra194 SoC to
>> +       work in host mode. There are two instances of PCIe controllers in
>> +       Tegra194. This controller can work either as EP or RC. In order to
>> +       enable host-specific features PCIE_TEGRA194_HOST must be selected and
>> +       in order to enable device-specific features PCIE_TEGRA194_EP must be
>> +       selected. This uses the DesignWare core.