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Date:   Tue, 27 Nov 2018 14:25:14 -0600
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Patrick Talbert <ptalbert@redhat.com>
Subject: Re: [Bug] SD card reader in Acer Aspire S5 broken in 4.20-rc
Message-ID: <20181127202514.GB112381@google.com>
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 <1675729.7aZxPkvRd8@aspire.rjw.lan>
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On Mon, Nov 26, 2018 at 11:37:20PM +0100, Rafael J. Wysocki wrote:
> On Monday, November 26, 2018 7:03:58 PM CET Rafael J. Wysocki wrote:
> > Hi Bjorn,
> > 
> > The SD card reader in my Acer Aspire S5 doesn't work with 4.20-rc.
> > 
> > Here's what lspci -v says about it (in a bad kernel):
> > 
> > 02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5209 PCI Express Card Reader 
> > (rev 01)
> >         Subsystem: Acer Incorporated [ALI] Device 0704
> >         Flags: bus master, fast devsel, latency 0, IRQ 35
> >         Memory at d9001000 (32-bit, non-prefetchable) [size=4K]
> >         Capabilities: [40] Power Management version 3
> >         Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
> >         Capabilities: [70] Express Endpoint, MSI 00
> >         Capabilities: [100] Advanced Error Reporting
> >         Capabilities: [140] Device Serial Number 00-00-00-01-00-4c-e0-00
> >         Kernel driver in use: rtsx_pci
> >         Kernel modules: rtsx_pci

Thanks a lot for bisecting this!

With a good kernel (v4.19 or v4.20-rc with 17c91487364f reverted),
would you mind collecting "lspci -vv" output, the dmesg log with
"pci=earlydump", and the FADT dump?

I'm interested in the initial state of the device at handoff from
BIOS, and what Linux changes even when aspm_disabled is set.

If we can't figure out a way to fix both this issue and the one fixed
by 17c91487364f, I guess the fallback will be to revert 17c91487364f
since it's better to allow a system that was previously broken to
remain broken than it is to break a system that previously worked.

But obviously I hope we can figure out a solution that fixes both
cases.

> > When it doesn't work, it doesn't generate any interrupts on device insertion
> > and removal and this seems to be reproducible 100% of the time.
> 
> So reverting 17c91487364f (PCI/ASPM: Do not initialize link state when
> aspm_disabled is set) on top of 4.20-rc4 makes the problem go away.
> 
> I guess that the device in question needs pcie_aspm_cap_init() to be
> called for it even though the FADT says "NO_ASPM".