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List:       linux-tegra
Subject:    Re: [PATCH 0/4] Add ASPM-L1 Substates support for Tegra
From:       Rajat Jain <rajatja () google ! com>
Date:       2017-10-30 16:57:56
Message-ID: CACK8Z6GvTYsPz-TXTKVSRbsYc=w=7OO130ftiJL_NXZOcbVNkg () mail ! gmail ! com
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On Mon, Oct 30, 2017 at 4:03 AM, Vidya Sagar <vidyas@nvidia.com> wrote:
> Tegra chips T210 and T186 support ASPM-L1 Substates (i.e. L1.1 and L1.2)
> This patch series
> - adds a generic API for root port controller drivers to
> override the default value of LTR L1.2 Threhold which otherwise comes from
> the same APIs weak implementation in aspm.c file

May be I'm imagining things, (and may be this is a question for
Bjorn), but is it possible to ever have a system that could have more
than 1 *type* of root port? If so, the current proposal only allows
for 1 value of LTR threshold (system wide) which may not be ideal.

> - applies fixups to reflect correct capability values for
> T_cmrt (Common Mode Restore Time) and
> T_pwr_on (Power On)
> and adjusts counter values for 19.2 MHz of clk_m
> - applies fixup specific to T210 to avoid unnecessary wake ups from L1.2 state
> 
> PCIe - ASPM L1 Sub States spec
> https://pcisig.com/sites/default/files/specification_documents/ECN_L1_PM_Substates_with_CLKREQ_31_May_2013_Rev10a.pdf
>  
> Testing Done on T210 and T186
> - ASPM-L1:
> Verified ASPM-L1 enablement by selecting PCIEASPM_POWERSAVE config
> With the help of Tegra rootport's internal counter registers, confirmed
> link entry in and out of ASPM-L1 state using USB3.0 add-on card, NVMe and NIC
> cards
> - ASPM-L1 SubStates:
> Verified ASPM-L1 Substates enablement by selecting PCIEASPM_POWER_SUPERSAVE config
> Confirmed link's entry into L1SS using Westren Digital NVMe card (with Sandisk
> Controller) using Tegra rootport's internal counter registers
> 
> Vidya Sagar (4):
> PCI/ASPM: Add API to supply LTR L1.2 threshold
> PCI: tegra: Enable ASPM-L1 capability advertisement
> PCI: tegra: Apply sw fixups to support ASPM-L1 Sub-States
> PCI: tegra: fixups to avoid unnecessary wakeup from ASPM-L1.2
> 
> drivers/pci/host/pci-tegra.c | 99 ++++++++++++++++++++++++++++++++++++++++++++
> drivers/pci/pcie/aspm.c      | 11 +++--
> include/linux/pci-aspm.h     |  6 +++
> 3 files changed, 113 insertions(+), 3 deletions(-)
> 
> --
> 2.7.4
> 
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