Re: [PATCH V2 0/7] Tegra PCIe end point config space map code refactoring

[Vidya Sagar <vidyas-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On Monday 23 October 2017 08:40 PM, Rob Herring wrote:
> On Mon, Oct 23, 2017 at 9:35 AM, Vidya Sagar <vidyas-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> wrote:
>> PCIe host controller in Tegra SoCs has 1GB of aperture available
>> for mapping end points config space, IO and BARs. In that, currently
>> 256MB is being reserved for mapping end points configuration space
>> which leaves less memory space available for mapping end points BARs
>> on some of the platforms.
>> This patch series attempts to use only 4K space from 1GB aperture to
>> access end points configuration space.
>>
>> Currently, this change benefits T20 and T186 in saving (i.e. repurposed
>> to use for BAR mapping) physical space as well as kernel virtual mapping space,
>> it saves only kernel virtual address space in T30, T124, T132 and T210.
>>
>> NOTE: Both driver and DT changes are inter-dependent and hence need to go together
> You are breaking compatibility with any other OS.
>
> Can't this easily be solved within the kernel by adjusting the
> resource size? To save the virtual space, you only need patch 1 and
> don't need the DT change. The DT change is just for phys address space
> for BARs.
In case of T20 & T186, DT change is required to re-purpose address space 
which otherwise
is used for config space mapping to map BARs. In case of other chips, DT 
changes
are also required because the 4K being used for mapping config space is 
taken from the
last 4K chunk of 256MB instead of first 4K chunk to align with driver 
change.
>> Testing Done on T124, T210 & T186:
>>   Enumeration and basic functionality of immediate devices
>>   Enumeration of devices behind a PCIe switch
>>   Complete 4K configuration space access
>>
>> Vidya Sagar (7):
>>    PCI: tegra: refactor config space mapping code
>>    ARM: tegra: limit PCIe config space mapping to 4K for T20
>>    ARM: tegra: limit PCIe config space mapping to 4K for T30
>>    ARM: tegra: limit PCIe config space mapping to 4K for T124
>>    ARM64: tegra: limit PCIe config space mapping to 4K for T132
>>    ARM64: tegra: limit PCIe config space mapping to 4K for T210
>>    ARM64: tegra: limit PCIe config space mapping to 4K for T186
>>
>>   arch/arm/boot/dts/tegra124.dtsi          |   2 +-
>>   arch/arm/boot/dts/tegra20.dtsi           |   8 +--
>>   arch/arm/boot/dts/tegra30.dtsi           |   2 +-
>>   arch/arm64/boot/dts/nvidia/tegra132.dtsi |   2 +-
>>   arch/arm64/boot/dts/nvidia/tegra186.dtsi |   8 +--
>>   arch/arm64/boot/dts/nvidia/tegra210.dtsi |   2 +-
>>   drivers/pci/host/pci-tegra.c             | 109 +++++++++----------------------
>>   7 files changed, 42 insertions(+), 91 deletions(-)
>>
>> --
>> 2.7.4
>>