On Mon, Feb 05, 2018 at 07:14:21PM +0000, Lorenzo Pieralisi wrote:
> On Mon, Jan 15, 2018 at 10:36:08AM +0100, Koen Vandeputte wrote:
> > The subordinate value indicates the highest bus number which can be
> > reached downstream though a certain device.
> >
> > Commit a20c7f36bd3d ("PCI: Do not allocate more buses than available in
> > parent")
> > ensures that downstream devices cannot assign busnumbers higher than the
> > upstream device subordinate number, which was indeed illogical.
> >
> > By default, dw_pcie_setup_rc() inits the Root Complex subordinate to a
> > value of 0x01.
> >
> > Due to this combined with above commit, enumeration stops digging deeper
> > downstream as soon as bus num 0x01 has been assigned, which is always
> > the case for a bridge device.
> >
> > This results in all devices behind a bridge bus to remain undetected, as
> > these would be connected to bus 0x02 or higher.
> >
> > Fix this by initializing the RC to a subordinate value of 0xff, which is
> > not altering hardware behaviour in any way, but informs probing
> > function pci_scan_bridge() later on which reads this value back from
> > register.
> >
> > Following nasty errors during boot are also fixed by this:
> >
> > [ 0.459145] pci_bus 0000:02: busn_res: can not insert [bus 02-ff]
> > under [bus 01] (conflicts with (null) [bus 01])
> > ...
> > [ 0.464515] pci_bus 0000:03: [bus 03] partially hidden behind bridge
> > 0000:01 [bus 01]
> > ...
> > [ 0.464892] pci_bus 0000:04: [bus 04] partially hidden behind bridge
> > 0000:01 [bus 01]
> > ...
> > [ 0.466488] pci_bus 0000:05: [bus 05] partially hidden behind bridge
> > 0000:01 [bus 01]
> > [ 0.466506] pci_bus 0000:02: busn_res: [bus 02-ff] end is updated to
> > 05
> > [ 0.466517] pci_bus 0000:02: busn_res: can not insert [bus 02-05]
> > under [bus 01] (conflicts with (null) [bus 01])
> > [ 0.466534] pci_bus 0000:02: [bus 02-05] partially hidden behind
> > bridge 0000:01 [bus 01]
> >
> > Fixes: a20c7f36bd3d ("PCI: Do not allocate more buses than available in
> > parent")
> > Signed-off-by: Koen Vandeputte <koen.vandeputte@xxxxxxxxxxxx>
> > Tested-by: Niklas Cassel <niklas.cassel@xxxxxxxx>
> > Cc: Binghui Wang <wangbinghui@xxxxxxxxxxxxx>
> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Cc: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
> > Cc: Jianguo Sun <sunjianguo1@xxxxxxxxxx>
> > Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
> > Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> > Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Cc: Minghuan Lian <minghuan.Lian@xxxxxxxxxxxxx>
> > Cc: Mingkai Hu <mingkai.hu@xxxxxxxxxxxxx>
> > Cc: Murali Karicheri <m-karicheri2@xxxxxx>
> > Cc: Pratyush Anand <pratyush.anand@xxxxxxxxx>
> > Cc: Richard Zhu <hongxing.zhu@xxxxxxx>
> > Cc: Roy Zang <tie-fei.zang@xxxxxxxxxxxxx>
> > Cc: Shawn Guo <shawn.guo@xxxxxxxxxx>
> > Cc: Stanimir Varbanov <svarbanov@xxxxxxxxxx>
> > Cc: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
> > Cc: Xiaowei Song <songxiaowei@xxxxxxxxxxxxx>
> > Cc: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
> > ---
> > drivers/pci/dwc/pcie-designware-host.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
>
> I would appreciate some testing from dwc host maintainers so that
> we can merge this patch, it is a bug fix that should be merged as
> soon as possible, please help Koen test it and provide feedback
> on the list.
BTW, this should have a stable tag so that it gets backported to stable
kernels. I guess whoever is applying the patch can add it so no need for
another revision.
