[0/2] Disable ASPM on GL9750 during a suspension

Message

Victor Ding Jan. 12, 2021, 4:02 a.m. UTC

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(-)