PCI trouble on mvebu (Turris Omnia)

Wed Mar 31 17:53:08 BST 2021

Pali Rohár <pali at kernel.org> writes:

> On Wednesday 31 March 2021 16:02:42 Toke Høiland-Jørgensen wrote:
>> Pali Rohár <pali at kernel.org> writes:
>> 
>> > On Friday 26 March 2021 18:51:42 Toke Høiland-Jørgensen wrote:
>> >> Pali Rohár <pali at kernel.org> writes:
>> >> > On Friday 26 March 2021 17:54:38 Toke Høiland-Jørgensen wrote:
>> >> >> So we have these
>> >> >> cases:
>> >> >> 
>> >> >> ASPM disabled:          ath9k, ath10k and mt76 cards all work
>> >> >> ASPM enabled, no patch: only mt76 card works
>> >> >> ASPM enabled + patch:   ath10k and mt76 cards work
>> >> >> 
>> >> >> So IDK, maybe the ath9k card needs a quirk as well? Or the mvebu board
>> >> >> is just generally flaky?
>> >> >
>> >> > I'm not sure. Maybe ASPM is somehow buggy on ath9k or needs some special
>> >> > handling. But issue is not at PCI config space as ath9k driver start
>> >> > initialization of this card. Needs also some debugging in ath9k driver
>> >> > if it prints that strange "mac chip rev" error.
>> >> 
>> >> Well that's just being output because it gets a revision that it doesn't
>> >> recognise - which it seems to be just reading from a register:
>> >> 
>> >> https://elixir.bootlin.com/linux/latest/source/drivers/net/wireless/ath/ath9k/hw.c#L255
>> >> 
>> >> The value returned is consistent with the value returned just being
>> >> 0xffffffff. Which from looking at ioread32() is the value being returned
>> >> on a failed read. So there's a driver bug there - the check against -EIO
>> >> here is obviously nonsensical:
>> >> 
>> >> https://elixir.bootlin.com/linux/latest/source/drivers/net/wireless/ath/ath9k/hw.c#L290
>> >> 
>> >> But the underlying cause appears to be that the read from the register
>> >> fails, which I suppose is related to something the PCI bus does?
>> >> 
>> >> > I think this issue should be handled separately. Could you report it
>> >> > also to ath9k mailing list (and CC me)? Maybe other ath developers would
>> >> > know some more details.
>> >> 
>> >> I'll send a patch for the nonsensical check above, but other than that I
>> >> think we're still in PCI land here, or?
>> >
>> > First, can you try to enable my quirk also for this ath9k card with ASPM
>> > enabled?
>> 
>> Yup, with this I get both devices working:
>> 
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index 8ff690c7679d..7e2f9c69f6b2 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -3583,6 +3583,7 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0034, quirk_no_bus_reset);
>>   * PCIe bridge has forced link speed to 2.5 GT/s via PCI_EXP_LNKCTL2 register.
>>   */
>>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c, quirk_no_bus_reset_and_no_retrain_link);
>> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x002e, quirk_no_bus_reset_and_no_retrain_link);
>>  
>>  /*
>>   * Root port on some Cavium CN8xxx chips do not successfully complete a bus
>
> Ok, thank you for testing!
>
> I'm seeing that testing unit 0x0030 (AR93xx) also needs this quirk, so I
> will mark all Atheros chips in above no bus reset list with no retrain
> link quirk.

SGTM.

>> >
>> > I have there another ath9k card which after toggling link retraining
>> > changes PCI device ID (really!) to 0xABCD. But lspci ...
>> >
>> > There is long story about broken ath9k cards that are reporting 0xABCD
>> > id on x86 machines with specific BIOS versions. It can be find in
>> > ath9k-devel mailing list archive:
>> >
>> > https://www.mail-archive.com/ath9k-devel@lists.ath9k.org/msg07529.html
>> >
>> > Maybe we now found root cause of this ABCD? If yes, then it also answers
>> > why above ath9k driver check fails (device id was changed) and also
>> > because kernel see correct id (kernel reads id before configuring ASPM
>> > and therefore before triggering link retraining).
>> >
>> >> >> > Can you send PCI device id of your ath9k card (lspci -nn)? Because all
>> >> >> > my tested ath9k cards have different PCI device id.
>> >> >> 
>> >> >> [root at omnia-arch ~]# lspci -nn
>> >> >> 00:01.0 PCI bridge [0604]: Marvell Technology Group Ltd. Device [11ab:6820] (rev 04)
>> >> >> 00:02.0 PCI bridge [0604]: Marvell Technology Group Ltd. Device [11ab:6820] (rev 04)
>> >> >> 00:03.0 PCI bridge [0604]: Marvell Technology Group Ltd. Device [11ab:6820] (rev 04)
>> >> >> 01:00.0 Network controller [0280]: Qualcomm Atheros AR9287 Wireless Network Adapter (PCI-Express) [168c:002e] (rev 01)
>> >> >> 02:00.0 Network controller [0280]: Qualcomm Atheros QCA986x/988x 802.11ac Wireless Network Adapter [168c:003c]
>> >> >
>> >> > That is fine. Also all ath9k testing cards have id 0x002e.
>> >
>> > Today I found out that lspci -nn may lie! Please send output from
>> > command: lspci -nn -x because real PCI device id can read only from -x
>> > hexdump output.
>> 
>> Without the quirk added to the ath9k:
>> 
>> 01:00.0 Network controller [0280]: Qualcomm Atheros AR9287 Wireless Network Adapter (PCI-Express) [168c:002e] (rev 01)
>> 00: 8c 16 2e 00 02 00 10 00 01 00 80 02 10 00 00 00
>> 10: 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 8c 16 a4 30
>> 30: 00 00 00 00 40 00 00 00 00 00 00 00 3d 01 00 00
>> 
>> 02:00.0 Network controller [0280]: Qualcomm Atheros QCA986x/988x 802.11ac Wireless Network Adapter [168c:003c]
>> 00: 8c 16 3c 00 46 05 10 00 00 00 80 02 10 00 00 00
>> 10: 04 00 20 e0 00 00 00 00 00 00 00 00 00 00 00 00
>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 30: 00 00 20 ea 40 00 00 00 00 00 00 00 3e 01 00 00
>> 
>> And with:
>> 
>> 01:00.0 Network controller [0280]: Qualcomm Atheros AR9287 Wireless Network Adapter (PCI-Express) [168c:002e] (rev 01)
>> 00: 8c 16 2e 00 46 01 10 00 01 00 80 02 10 00 00 00
>> 10: 04 00 00 e0 00 00 00 00 00 00 00 00 00 00 00 00
>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 8c 16 a4 30
>> 30: 00 00 00 00 40 00 00 00 00 00 00 00 3d 01 00 00
>> 
>> 02:00.0 Network controller [0280]: Qualcomm Atheros QCA986x/988x 802.11ac Wireless Network Adapter [168c:003c]
>> 00: 8c 16 3c 00 46 05 10 00 00 00 80 02 10 00 00 00
>> 10: 04 00 20 e0 00 00 00 00 00 00 00 00 00 00 00 00
>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 30: 00 00 20 ea 40 00 00 00 00 00 00 00 3e 01 00 00
>> 
>
> Yesterday both MJ and Bjorn told me to use lspci '-b' switch which
> instruct lspci to parse capabilities from config space (instead of
> kernel cache).
>
> Could you try to run 'lspci -nn -vv' and 'lspci -nn -vv -b' and compare
> results? If something changes?

Without -b there seems to be some [size=XX] suffixes to some lines, and
there are some AtomicOpsCap lines that are not there with -b. Also, the
IRQ number and memory offset for ath10k changed like this:

-	Interrupt: pin A routed to IRQ 63
-	Region 0: Memory at e0200000 (64-bit, non-prefetchable) [size=2M]
-	Expansion ROM at e0400000 [disabled] [size=64K]
+	Interrupt: pin A routed to IRQ 62
+	Region 0: Memory at e0200000 (64-bit, non-prefetchable)
+	Expansion ROM at ea200000 [disabled]

> Anyway I have discussion with Adrian Chadd about 0xABCD issue and these
> Qualcomm/Atheros cards. When post-AR9300 card is not initialized it
> reports PCI device id 0xABCD. Pre-AR9300 cards should report correct PCI
> device id even when it is not initialized. WLE200 is AR9287-based, so it
> reports always correct id, should not change it during usage.

Right, makes sense.

> But seems that also this AR9287 has issue with EEPROM/OTP as you figured
> out that ath9k driver is not able to read some device id from internal
> register. So please prepare patch for fixing -EIO in ath9k.

Yup, already did, just forgot to Cc you (sorry about that):
https://patchwork.kernel.org/project/linux-wireless/patch/20210326180819.142480-1-toke@redhat.com/

> PCI vendor & device id is in first 4 bytes and as you can see it is
> correct and was not changed.
>
> So I guess lspci output would not change for this card.
>
>> Is that change in bytes 5 and 6 significant?
>
> At offset 0x04 is 16bit PCI Command Register.
>
> In second (with) output is set bit 2 which means that Bus Mastering is
> enabled. This is normal and required when card communicate with system.
> Then is enabled bit 6 (Parity Error Response) and bit 8 (SERR# Enable),
> both for error reporting. This is normal when device is active.
>
> So nothing suspicious here.

Alright, cool. Thanks a lot for your help with this :)

-Toke