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From: Andy S. <and...@gm...> - 2020-05-22 08:59:16
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+Cc: Adrian On Fri, May 22, 2020 at 9:15 AM la...@ap... <la...@ap...> wrote: > > Thanks David! > > With this I tracked down the SD Card Reader (Genesys Logic, Inc Device 9755) as the culprit. > These are standard in many ThinkPads. > The curious part is that resume from suspend (S3 or S0iX) also fixes the problem. > Looks like the driver is not initializing correctly at boot time. > > Transcript: > > $ cat /sys/kernel/debug/pmc_core/ltr_show | grep SOUTHPORT > SOUTHPORT_A LTR: RAW: 0x88018c01 Non-Snoop(ns): 1024 Snoop(ns): 32768 > SOUTHPORT_B LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 > SOUTHPORT_C LTR: RAW: 0x9f409f4 Non-Snoop(ns): 0 Snoop(ns): 0 > SOUTHPORT_D LTR: RAW: 0x88aa88aa Non-Snoop(ns): 174080 Snoop(ns): 174080 > SOUTHPORT_E LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 > > $ lspci -t > -[0000:00]-+-00.0 > +-01.0-[01]--+-00.0 > | \-00.1 > +-02.0 > +-04.0 > +-08.0 > +-12.0 > +-14.0 > +-14.2 > +-15.0 > +-16.0 > +-1c.0-[53]----00.0 > +-1d.0-[02]----00.0 > +-1d.6-[52]----00.0 > +-1e.0 > +-1f.0 > +-1f.3 > +-1f.4 > +-1f.5 > \-1f.6 > > $ lspci | grep 53 > 53:00.0 SD Host controller: Genesys Logic, Inc Device 9755 > > $ cat /sys/bus/pci/devices/0000\:53\:00.0/power/control > auto > > $ echo 1 > /sys/bus/pci/devices/0000\:53\:00.0/remove > 1 > > $ cat /sys/kernel/debug/pmc_core/ltr_show | grep SOUTHPORT > SOUTHPORT_A LTR: RAW: 0x8010c01 Non-Snoop(ns): 0 Snoop(ns): 0 > SOUTHPORT_B LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 > SOUTHPORT_C LTR: RAW: 0x9f409f4 Non-Snoop(ns): 0 Snoop(ns): 0 > SOUTHPORT_D LTR: RAW: 0x8c548c54 Non-Snoop(ns): 2752512 Snoop(ns): 2752512 > SOUTHPORT_E LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 > > Cheers. > > -- Lars > > > > > > > > > On Tuesday, May 19, 2020, 9:03:53 AM PDT, David E. Box <dav...@li...> wrote: > > > > > > > > > Does anybody know what's going on or how to debug this further? > > > > As stated above, I was able to work around this problem by > > > > ignoring SOUTHPORT_A via /sys/kernel/debug/pmc_core/ltr_ignore. > > > > There has to be a better way, and I'm sure I'm not the only one > > > > running into this. > > ltr_show shows the PMC's (Power Management Controller) view of SoC > devices and busses. The SOUTHPORTs are the PCIe root ports on your > system. When you run lspci they are the PCI bridges. Generally, the > bridges are enumerated in the same order as the SOUTHPORTs, so > SOUTHPORT_A is your first bridge and the device attached to it (shown > in lspci -t) is the device that was blocking deeper PC states according > to your debug. > > Determine what this device is on your system. If the ltr was low it's > because that is what the device requested. You should first check that > runtime pm is enabled for the device. To do this, check the control > file in /sys/bus/pci/devices/<SSSS:BB:DD.F>/power, where SSSS:BB:DD.F > is the enumeration of your device as shown in lspci. If it is 'on' then > runtime pm is disabled. To enable it echo 'auto' into the file with > root privileges. Enabling runtime pm should allow the driver to reduce > functionality of the device when idle. This should lead to a larger > latency request on the PCI bus which should be reflected in ltr_show. > You can see if the device is actually runtime suspended and how much > time it's been suspended (or active) by reading the associated files in > the power folder. > > If this doesn't work, then it's possible that your device doesn't > support runtime pm. This may be purposely for reliability reasons or > the driver may just lack support. Check forums discussing issues with > the device and look for possible options in the driver to force pm > support (generally this will be centered around enabling ASPM). > > You can also download powertop to see the package c-state residencies > more clearly as percentages of time. powertop also has a tunables tab > that will show the status of runtime pm on all devices on the system > and allow you to enable them individually. > > > David > -- With Best Regards, Andy Shevchenko |
