[PATCH v7 0/5] PCI: qcom: Add system suspend & resume support

[Krishna chaitanya chundru <quic_krichai@quicinc.com>]

Few PCIe endpoints like NVMe and WLANs are always expecting the device
to be in D0 state and the link to be active (or in l1ss) all the
time (including in S3 state).

This patch series adds this support for allowing the system to enter
S3 state (and further low power states) with PCIe Device being in D0
state and with link being in l1ss on qcom platforms.

And to get to the lowest power state on Qcom SoC, all the clocks need
to be voted off. Since PCIe clocks are managed by qcom platform driver,
this logic was added to the qcom platform driver.

And when we turn off PCIe PHY-specific clocks, PHY may go off and along
with it the link also will go down. To retain, the link state in l1ss with
PHY clocks turned off, we need park PCIe PHY in the power-down state so
that it can maintain the link state in l1ss with the help of the always-on
power domain (aka MX).
To support this PHY Power-down state PHY driver has been updated with new
interface APIs.

Its observed that access to Ep PCIe space to mask MSI/MSIX is happening at
the very late stage of suspend path (access by affinity changes while
making CPUs offline during suspend, this will happen after devices are
suspended (after all phases of suspend ops)). If we turn off clocks in any
PM callback, afterwards running into crashes due to un-clocked access due
to above mentioned MSI/MSIx access. So, we are making use of syscore
framework to turn off the PCIe clocks which will be called after making
CPUs offline.

During this process, The controller should remain powered on. For this made
changes to GDSC. 

Few endpoints are taking time more time to settle the link in L1ss.
So Waiting for max time of 200ms for the link to be stable in L1ss.

Krishna chaitanya chundru (5):
  PCI: qcom: Add system suspend and resume support
  PCI: qcom: Add retry logic for link to be stable in L1ss
  phy: core: Add support for phy suspend & resume
  phy: qcom: Add power suspend & resume callbacks to pcie phy
  clk: qcom: Enabling PCIe GDSC retention

 drivers/clk/qcom/gcc-sc7280.c            |   2 +-
 drivers/pci/controller/dwc/pcie-qcom.c   | 163 ++++++++++++++++++++++++++++++-
 drivers/phy/phy-core.c                   |  30 ++++++
 drivers/phy/qualcomm/phy-qcom-qmp-pcie.c |  50 ++++++++++
 include/linux/phy/phy.h                  |  20 ++++
 5 files changed, 263 insertions(+), 2 deletions(-)

-- 
2.7.4