[Bug] SD card reader in Acer Aspire S5 broken in 4.20-rc

[Rafael J. Wysocki]

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

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.

Bisection turned up

commit de468b755464426c276df2daf1e54bcd64186020
Merge: b1801bf05964 d6112f8def51
Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Date:   Sat Oct 20 11:45:28 2018 -0500

    Merge branch 'pci/enumeration'
    
      - Remove x86 and arm64 node-local allocation for host bridge structures
        (Punit Agrawal)
    
      - Pay attention to device-specific _PXM node values (Jonathan Cameron)
    
      - Support new Immediate Readiness bit (Felipe Balbi)
    
    * pci/enumeration:
      PCI: Add support for Immediate Readiness
      ACPI/PCI: Pay attention to device-specific _PXM node values
      x86/PCI: Remove node-local allocation when initialising host controller
      arm64: PCI: Remove node-local allocations when initialising host controller

as the first bad commit, but the "PCI: Add support for Immediate Readiness"
one was tested as "good" (full bisect log is attached).

I wonder if you have any ideas on what to check?

Cheers,
Rafael
git bisect start
# good: [84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d] Linux 4.19
git bisect good 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d
# bad: [2e6e902d185027f8e3cb8b7305238f7e35d6a436] Linux 4.20-rc4
git bisect bad 2e6e902d185027f8e3cb8b7305238f7e35d6a436
# bad: [18d0eae30e6a4f8644d589243d7ac1d70d29203d] Merge tag 'char-misc-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
git bisect bad 18d0eae30e6a4f8644d589243d7ac1d70d29203d
# good: [50b825d7e87f4cff7070df6eb26390152bb29537] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
git bisect good 50b825d7e87f4cff7070df6eb26390152bb29537
# bad: [3acbd2de6bc3af215c6ed7732dfc097d1e238503] Merge tag 'sound-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
git bisect bad 3acbd2de6bc3af215c6ed7732dfc097d1e238503
# good: [a41efc2a0f68cea26665ab9e6d991c9bf33b3f59] Merge tag 'dmaengine-4.20-rc1' of git://git.infradead.org/users/vkoul/slave-dma
git bisect good a41efc2a0f68cea26665ab9e6d991c9bf33b3f59
# bad: [d49f8a52b15bf35db778035340d8a673149f9f93] Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
git bisect bad d49f8a52b15bf35db778035340d8a673149f9f93
# good: [6c404a68bf83b4135a8a9aa1c388ebdf98e8ba7f] scsi: dc395x: fix DMA API usage in sg_update_list
git bisect good 6c404a68bf83b4135a8a9aa1c388ebdf98e8ba7f
# bad: [61ce5809570b38710f08ebfcd44a5b067eeee77d] Merge branch 'remotes/lorenzo/pci/cadence'
git bisect bad 61ce5809570b38710f08ebfcd44a5b067eeee77d
# good: [e51cd9ce5dd3b10f9e67a30a4dc00fc1fa80c673] PCI/AER: Refactor error injection fallbacks
git bisect good e51cd9ce5dd3b10f9e67a30a4dc00fc1fa80c673
# bad: [ee8360fdafac54eefd0df69fbd99338896cf806b] Merge branch 'pci/misc'
git bisect bad ee8360fdafac54eefd0df69fbd99338896cf806b
# good: [fb513f60ea58f096be7006f899e2181762af37cb] NTB: switchtec_ntb: Update switchtec documentation with prerequisites for NTB
git bisect good fb513f60ea58f096be7006f899e2181762af37cb
# good: [b1801bf05964321d79fbbeae96c8ab09da2e2e49] Merge branch 'pci/aspm'
git bisect good b1801bf05964321d79fbbeae96c8ab09da2e2e49
# good: [d6112f8def514e019658bcc9b57d53acdb71ca3f] PCI: Add support for Immediate Readiness
git bisect good d6112f8def514e019658bcc9b57d53acdb71ca3f
# bad: [20634dc361e1c5fe2dae380a7d0a21ca7f32c4f7] Merge branch 'pci/hotplug'
git bisect bad 20634dc361e1c5fe2dae380a7d0a21ca7f32c4f7
# bad: [de468b755464426c276df2daf1e54bcd64186020] Merge branch 'pci/enumeration'
git bisect bad de468b755464426c276df2daf1e54bcd64186020
# first bad commit: [de468b755464426c276df2daf1e54bcd64186020] Merge branch 'pci/enumeration'