[Linuxppc-users] Fedora 28-1.1 taking 30 seconds to discover/enable PCIe adapter after link disable/enable

[Mike Bieker]

On x86 system, discovering/enabling a PCIe adapter after PCIe link
disable/enable takes less than a second.  However, on Power Systems it
takes 30 seconds or more.



Here is the process we are using to test:

1)        Boot system and verify that link is up between IBM Root Port and
our Atlas PCIe Gen4x16 switch with no errors – ‘lspci –s 034:01:00.0 –vvv’

2)        Set Link Disable bit (Bit 4) in PCIe Link Control register of
Root Port - ‘setpci –s 034:00:00.0 58.w=0018’.

3)        Verify that link is disabled between Root and Atlas – ‘setpci –s
034:00:00.0 58.w’ should show that link disable bit is set.  Can also
execute ‘lspci’ and see that link is down between Root Port and Atlas.

4)        Clear Link Disable bit in PCIe Link Control register of Root Port
– ‘setpci –s 034:00:00.0 58.w=0008’

5)        Wait 5 seconds  - ‘sleep 5’

6)        Check that that link between Root Port and Atlas is enabled and
at proper rate and width (Gen4x16) – ‘lspci –s 034:01:00.0 –vvv’.  This is
where error occurs because link is not up.  If I keep trying lspci, after
30 to 60 seconds the port returns valid data.  Why does Fedora on Power
Systems take so long to link up and discover the adapter after link
disable/enable?



Thanks,

Mike
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