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Date:   Tue, 12 Jan 2021 04:02:03 +0000
Message-Id: <20210112040205.4117303-1-victording@google.com>
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Subject: [PATCH 0/2] Disable ASPM on GL9750 during a suspension
From:   Victor Ding <victording@google.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>,
        Adrian Hunter <adrian.hunter@intel.com>
Cc:     Ben Chuang <ben.chuang@genesyslogic.com.tw>,
        Bjorn Helgaas <helgaas@kernel.org>,
        linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mmc@vger.kernel.org, Victor Ding <victording@google.com>,
        Alex Levin <levinale@google.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        "Saheed O. Bolarinwa" <refactormyself@gmail.com>,
        Sean Paul <seanpaul@chromium.org>,
        Sukumar Ghorai <sukumar.ghorai@intel.com>,
        Yicong Yang <yangyicong@hisilicon.com>
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Precedence: bulk


GL9750 SD Host Controller has a 3100us PortTPowerOnTime; however, it
enters L1.2 after only ~4us inactivity per PCIe trace. During a
suspend/resume process, PCI access operations are frequently longer than
4us apart. Therefore, the device frequently enters and leaves L1.2 during
this process, causing longer than desirable suspend/resume time. The total
time cost due to this L1.2 exit latency could add up to ~200ms.

Considering that PCI access operations are fairly close to each other
(though sometimes > 4us), the actual time the device could stay in L1.2 is
negligible. Therefore, the little power-saving benefit from ASPM during
suspend/resume does not overweight the performance degradation caused by
long L1.2 exit latency.

Therefore, I am proposing to disable ASPM during a suspend/resume process.


Victor Ding (2):
  PCI/ASPM: Disable ASPM until its LTR and L1ss state is restored
  mmc: sdhci-pci-gli: Disable ASPM during a suspension

 drivers/mmc/host/sdhci-pci-core.c |  2 +-
 drivers/mmc/host/sdhci-pci-gli.c  | 46 +++++++++++++++++++++++++++++--
 drivers/mmc/host/sdhci-pci.h      |  1 +
 drivers/pci/pci.c                 | 11 ++++++++
 drivers/pci/pci.h                 |  2 ++
 drivers/pci/pcie/aspm.c           |  2 +-
 6 files changed, 60 insertions(+), 4 deletions(-)

-- 
2.30.0.284.gd98b1dd5eaa7-goog