Re: [Bug 216094] New: pci-mvebu: SATA HDDs via 88SE6121 AHCI fail with Marvell 88F6281 PCIe

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Jun 07, 2022 at 07:29:03AM +0000, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=216094
> 
>            Summary: pci-mvebu: SATA HDDs via 88SE6121 AHCI fail with
>                     Marvell 88F6281 PCIe
>     Kernel Version: 3.16 ... 5.10
>           Reporter: hajo-linux-bugzilla@noerenberg.de
>                 CC: pali@kernel.org
>         Regression: No
> 
> I would like to continue the SATA-related topic started with Pali
> Rohár at the U-Boot mailing list [1]. I have analysed the issue
> further and come the following conclusion that it is related to the
> PCIe subsystem:
> 
> SATA-2 and SATA-3 hard disks connected to a 88SE6121 (AHCI)
> controller, wired via PCIe to the 88F6281 SoC fail to operate
> ("failed to IDENTIFY" ... "qc timeout") when the pci-mvebu driver
> (Kernel 3.16 .. 5.10 Debian) is in use.

Please attach the complete dmesg logs showing this issue.

From your lspci output with v3.2, the SATA controller is at 00:01.0:

  00:01.0 IDE [0101]: Marvell 88SE6121 SATA II

The v3.16 (with DTB) lspci output is essentially the same except the
controller is at 01:00.0:

  01:00.0 IDE [0101]: Marvell 88SE6121 SATA II

The ahci driver is bound in both cases.  The PCI address and I/O port
assignment differences are of no consequence unless some mvebu driver
defect keeps them from working.

I think what we need is a complete dmesg log and DTB from the newest
possible kernel that fails, plus the same logs from the newest kernel
that works.

> More details:
> 
> - The problem does not exist in 2.6 and 3.16 kernels. With the old
> mach-kirkwood/pcie.c driver all SATA-2/3 hard disks work correctly.
> Especially with a 3.16 kernel it is possible to have identical
> ATA/AHCI drivers but try both PCIe drivers: without DTB ->
> mach-kirkwood -> SATA-2/3 HDDs work; with DTB -> mach-mvebu -> HDDs
> fail.
> 
> - The problem is specific to SATA-2/3 HDDs. Very old SATA-1-only
> HDDs work without problems. This might be related to the available
> data lanes, DMA or other bandwidth-related things -- I can only
> guess. Interestingly it does not help to limit SATA speed
> (libata.force=1.5G ...) with SATA-2/3 HDDs, only 'pure' SATA-1 HDDs
> work with pci-mvebu.
> 
> - The problem was identified with the Seagate Blackarmor NAS440
> hardware. Forum posts show that other users experience similar
> problems with the (very similar) Iomega ix4-200d NAS [2].
> 
> - Within patched U-Boot [3] all (Sata-1/2/3) HDDs always work. Same
> for the 88F6281 SoC onboard SATA ports (sata_mv - not connected via
> PCIe).
> 
> - The mach-kirkwood driver operates the 6281 as class "Host bridge
> [0600]" with Cap "Express (v1) Root Port", the mach-mvebu driver as
> class "PCI bridge [0604]" with "Express (v2) Root Port"
> [4][5][6][7]. Notably the v1/v2, cache line size 32/64 or the
> missing interrupt route might be a key difference.
> 
> From the sources I see that all PCI drivers (mach-kirkwood,
> mach-mvebu and U-Boot) do various unconventional 'magic' things
> (rewriting PCI class of the root complex, changing capabilitys, host
> emulation and so on). This is the point where I currently get lost
> and ask for your help.

> [1] https://lists.denx.de/pipermail/u-boot/2022-March/479197.html
> [2] https://forum.doozan.com/read.php?2,94079,95519#msg-95519
> [3] https://lists.denx.de/pipermail/u-boot/2022-March/479227.html
> [4] lspci Linux version 3.2.0-4-kirkwood mach-kirkwood/pci.c: HDDs ok
> [5] lspci Linux version 3.16.0-0.bpo.4-kirkwood - with DTB -> mvebu-pci: HDDs
> fail
> [6] lspci Linux version 3.16.0-0.bpo.4-kirkwood - without DTB ->
> mach-kirkwood/pci.c: HDDs ok
> [7] lspci Linux version 5.10.0-11-marvell (Debian bullseye) mvebu-pci: HDDs
> fail