Hi Lucas,
I found that imx6q suspend/resume is broken on 3.16-rc, and it works
just fine if PCIe support is built out. However the issue was not
exposed on 3.15, so I suspect the PCIe driver change merged in 3.16
is part of the cause.
$ echo mem > /sys/power/state
PM: Syncing filesystems ... done.
Freezing user space processes ... (elapsed 0.002 seconds) done.
Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done.
sd 0:0:0:0: [sda] Synchronizing SCSI cache
sd 0:0:0:0: [sda] Stopping disk
PM: suspend of devices complete after 85.695 msecs
PM: suspend devices took 0.100 seconds
PM: late suspend of devices complete after 6.786 msecs
PM: noirq suspend of devices complete after 6.228 msecs
Disabling non-boot CPUs ...
CPU1: shutdown
CPU2: shutdown
CPU3: shutdown
Enabling non-boot CPUs ...
CPU1: Booted secondary processor
CPU1 is up
CPU2: Booted secondary processor
CPU2 is up
CPU3: Booted secondary processor
CPU3 is up
The issue is actually with resume procedure. I noticed that Richard
added the following change in FSL kernel tree, which seems to fix the
issue.
@@ -229,6 +232,22 @@ static int imx6_suspend_finish(unsigned long val)
static int imx6_pm_enter(suspend_state_t state)
{
+ struct regmap *gpr;
+
+ /*
+ * L2 can exit by 'reset' or Inband beacon (from remote EP)
+ * toggling phy_powerdown has same effect as 'inband beacon'
+ * So, toggle bit18 of GPR1, to fix errata
+ * "PCIe PCIe does not support L2 Power Down"
+ */
+ gpr = syscon_regmap_lookup_by_compatible("fsl,imx6q-iomuxc-gpr");
+ if (IS_ERR(gpr)) {
+ pr_err("failed to find fsl,imx6q-iomux-gpr regmap\n");
+ return PTR_ERR(gpr);
+ }
+ regmap_update_bits(gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD,
+ IMX6Q_GPR1_PCIE_TEST_PD);
+
switch (state) {
case PM_SUSPEND_STANDBY:
imx6_set_lpm(STOP_POWER_ON);
@@ -258,6 +277,15 @@ static int imx6_pm_enter(suspend_state_t state)
return -EINVAL;
}
+ /*
+ * L2 can exit by 'reset' or Inband beacon (from remote EP)
+ * toggling phy_powerdown has same effect as 'inband beacon'
+ * So, toggle bit18 of GPR1, to fix errata
+ * "PCIe PCIe does not support L2 Power Down"
+ */
+ regmap_update_bits(gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD,
+ !IMX6Q_GPR1_PCIE_TEST_PD);
+
return 0;
}
And I copied the details of the errata as below.
ERR005723 PCIe: PCIe does not support L2 power down
Description:
When PCIe works as Root Complex, it can exit L2 mode only through reset.
Since PCIe does not have a dedicated reset control bit, it cannot exit
L2 mode.
Projected Impact:
PCIe does not support L2 power down.
Workarounds:
The PCIe can be put into PDDQ mode to save PCIe PHY power and wake up
only by the OOB (Out of Band) wakeup signal (since wakeup by a beacon
from link partner is not supported) driven from the link partner (End
Point). This signal could be used as a GPIO interrupt to exit this mode.
The limitation of this workaround is that the link partner cannot be put
into L2 mode.
As I have no knowledge of how PCIe works, I provided all the info I
found here to kick the discussion. Hopefully, we can find a proper fix
to get suspend/resume back to work.
Shawn
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