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Subject: Re: [RFC PATCH] Revert "arm64: PCI: Exclude ACPI "consumer" resources
 from host bridge windows"
To:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Will Deacon <will@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20210510234020.1330087-1-luzmaximilian@gmail.com>
 <20210526205836.GA20320@willie-the-truck> <20210527093200.GA16444@lpieralisi>
From:   Maximilian Luz <luzmaximilian@gmail.com>
Message-ID: <e90401dc-e146-743d-93c7-8525ac0f639e@gmail.com>
Date:   Thu, 27 May 2021 13:31:17 +0200
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On 5/27/21 11:32 AM, Lorenzo Pieralisi wrote:
> On Wed, May 26, 2021 at 09:58:36PM +0100, Will Deacon wrote:
>> On Tue, May 11, 2021 at 01:40:20AM +0200, Maximilian Luz wrote:
>>> The Microsoft Surface Pro X has host bridges defined as
>>>
>>>      Name (_HID, EisaId ("PNP0A08") /* PCI Express Bus */)  // _HID: Hardware ID
>>>      Name (_CID, EisaId ("PNP0A03") /* PCI Bus */)  // _CID: Compatible ID
>>>
>>>      Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
>>>      {
>>>          Name (RBUF, ResourceTemplate ()
>>>          {
>>>              Memory32Fixed (ReadWrite,
>>>                  0x60200000,         // Address Base
>>>                  0x01DF0000,         // Address Length
>>>                  )
>>>              WordBusNumber (ResourceProducer, MinFixed, MaxFixed, PosDecode,
>>>                  0x0000,             // Granularity
>>>                  0x0000,             // Range Minimum
>>>                  0x0001,             // Range Maximum
>>>                  0x0000,             // Translation Offset
>>>                  0x0002,             // Length
>>>                  ,, )
>>>          })
>>>          Return (RBUF) /* \_SB_.PCI0._CRS.RBUF */
>>>      }
>>>
>>> meaning that the memory resources aren't (explicitly) defined as
>>> "producers", i.e. host bridge windows.
>>>
>>> Commit 8fd4391ee717 ("arm64: PCI: Exclude ACPI "consumer" resources from
>>> host bridge windows") introduced a check that removes such resources,
>>> causing BAR allocation failures later on:
>>>
>>>      [ 0.150731] pci 0002:00:00.0: BAR 14: no space for [mem size 0x00100000]
>>>      [ 0.150744] pci 0002:00:00.0: BAR 14: failed to assign [mem size 0x00100000]
>>>      [ 0.150758] pci 0002:01:00.0: BAR 0: no space for [mem size 0x00004000 64bit]
>>>      [ 0.150769] pci 0002:01:00.0: BAR 0: failed to assign [mem size 0x00004000 64bit]
>>>
>>> This eventually prevents the PCIe NVME drive from being accessible.
>>>
>>> On x86 we already skip the check for producer/window due to some history
>>> with negligent firmware. It seems that Microsoft is intent on continuing
>>> that history on their ARM devices, so let's drop that check here too.
>>>
>>> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
>>> ---
>>>
>>> Please note: I am not sure if this is the right way to fix that, e.g. I
>>> don't know if any additional checks like on IA64 or x86 might be
>>> required instead, or if this might break things on other devices. So
>>> please consider this more as a bug report rather than a fix.
>>>
>>> Apologies for the re-send, I seem to have unintentionally added a blank
>>> line before the subject.
>>>
>>> ---
>>>   arch/arm64/kernel/pci.c | 14 --------------
>>>   1 file changed, 14 deletions(-)
>>
>> Adding Lorenzo to cc, as he'll have a much better idea about this than me.
>>
>> This is:
>>
>> https://lore.kernel.org/r/20210510234020.1330087-1-luzmaximilian@gmail.com
> 
> Sigh. We can't apply this patch since it would trigger regressions on
> other platforms (IIUC the root complex registers would end up in the
> host bridge memory windows).
> 
> I am not keen on reverting commit 8fd4391ee717 because it does the
> right thing.
> 
> I think this requires a quirk and immediate reporting to Microsoft.

Since I wrote this I have found other arm64 devices with the same
problem. I don't think that this is Microsoft exclusive anymore, but
rather that this is a Qualcomm problem (Qualcomm SoC seems to be the
common thread). See e.g. DSDTs in [1]. So it should probably be reported
to them.

Regards,
Max

[1]: https://github.com/aarch64-laptops/build/tree/dfce25bc12655713c7e1e0422b191e9c944e4fb2/misc