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Re: rtl8821ae dbi read question

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On 11/05/2017 02:53 PM, Nik Nyby wrote:
On 11/05/2017 11:50 AM, Larry Finger wrote:

If you read the commit message for commit b8b8b16352cd, you will find that we do not understand why using a byte read causes failure, but reverting the change so that it is a word read made it function again. The "fix" was found by a user doing bisection, and verified on my system, where the RTL8821AE has stable connections. The transfer rates take wild swings, but the connection is not dropped.

If you NIC behaves differently, then you will need to help us debug the problem. If you had a kernel that worked, then you might try bisection.

I just tested on kernels 4.12 and 4.13 - my connection gets dropped on those kernels as well. Right now I'm using 4.14-rc7.

If that is not possible, you might try various combinations of module parameters aspm, int_clear, and msi
Thanks for these suggestions. Disabling ASPM solves my connection dropping issue! Previously, I was getting disconnected around 10 seconds after starting "git clone" on a large git repository. Now, I haven't seen the connection drop once.

I can help debug the issue. I'm using a Lenovo Ideapad 320-15ABR laptop. Here's the lspci -vv info for my NIC:

01:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8821AE 802.11ac PCIe Wireless Network Adapter
         Subsystem: Lenovo RTL8821AE 802.11ac PCIe Wireless Network Adapter
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
         Latency: 0, Cache Line Size: 32 bytes
         Interrupt: pin A routed to IRQ 33
         Region 0: I/O ports at 2000 [size=256]
         Region 2: Memory at f0b00000 (64-bit, non-prefetchable) [size=16K]
         Capabilities: <access denied>
         Kernel driver in use: rtl8821ae

If "aspm=0" fixes your issue, then there is nothing more to debug. That option is there to handle cases where the PCI connection does not behave the way that most do. This condition seems to be most common on Lenovo machines. Frequently, ASPM problems are accompanied by PCI errors, but that seems not to be the case for your machine. Create a suitable .conf file in /etc/modprobe.d/ and you should be OK.

Larry





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