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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Patrick Talbert <ptalbert@redhat.com>,
        Linux ACPI <linux-acpi@vger.kernel.org>
Subject: Re: [Bug] SD card reader in Acer Aspire S5 broken in 4.20-rc
Date:   Tue, 27 Nov 2018 23:32:52 +0100
Message-ID: <2589393.XVIVmOtOXj@aspire.rjw.lan>
In-Reply-To: <20181127202514.GB112381@google.com>
References: <2960808.4YCFhzuD0k@aspire.rjw.lan> <1675729.7aZxPkvRd8@aspire.rjw.lan> <20181127202514.GB112381@google.com>
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On Tuesday, November 27, 2018 9:25:14 PM CET Bjorn Helgaas wrote:
> 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'll do that tomorrow.

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

OK

> 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.

Well, depending on how many systems are affected by the issues fixed by
17c91487364f IMO.

Arguably, if the FADT says "NO_ASPM", then the platform should not need the
OS to initialize ASPM to work.  I guess a manual workaround (like an extra
kernel command line option or similar) should suffice in this particular
case.

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

Of course.