[RFC] PCI: skip pci host bridge as early as possible

[Lucas Stach]

Hi Antony,

I don't think ignoring the host bridge is the right thing to do in the
first place and unfortunately I'm unable to reproduce your problem.

Am Dienstag, den 09.06.2015, 22:51 +0300 schrieb Antony Pavlov:
> The barebox' pci_scan_bus() function first tries to setup GT64120
> host bridge BARs but fails:
> 
>     barebox:/ dmesg
>     pci: pci_scan_bus for bus 0
>     pci:  last_io = 0x18000000, last_mem = 0x10000000, last_mem_pref = 0x00000000
>     pci: class = 00000600, hdr_type = 00000000
>     pci: 00:00 [11ab:4620]
>     pci: pbar0: mask=00000008 NP memory 0 bytes
>     pci: pbar1: mask=01000008 NP memory -16777216 bytes
>     pci: pbar2: mask=1c000000 NP memory -469762048 bytes
>     pci: BAR does not fit within bus np-mem res
>     pci: skip pci host bridge
> 
I can reproduce up until here. But the messages suggest that barebox is
in fact skipping the BAR configuration, so this isn't really a problem.

This might be improved by checking for invalid BAR sizes before trying
to fit them.

> so PCI host bridge and all discovered devices are misconfigured, e.g.
> miitool can't find rtl8139 emulated NIC tranceiver:
> 
>     rtl8139_eth pci-10ec:8139.0: rtl8139 (rev 20) at 90: 0200 (base=8f000000)
>     rtl8139_eth pci-10ec:8139.0: enabling bus mastering
>     ...
>     barebox:/ miitool
>     miibus0: registered phy as /dev/phy0
>     phy0: eth0:   No MII transceiver present!.
> 

Works for me:

barebox:/ miitool
miibus0: registered phy as /dev/phy0
phy0: eth0: no autonegotiation, 100baseTx-FD flow-control, link ok

> Here is linux-3.19 GT64120 host bridge discovery log:
> 
>     PCI host bridge to bus 0000:00
>     pci_bus 0000:00: root bus resource [mem 0x10000000-0x17ffffff]
>     pci_bus 0000:00: root bus resource [io  0x1000-0x1fffff]
>     pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
>     pci 0000:00:00.0: [Firmware Bug]: reg 0x14: invalid BAR (can't size)
>     pci 0000:00:00.0: [Firmware Bug]: reg 0x18: invalid BAR (can't size)
>     pci 0000:00:00.0: [Firmware Bug]: reg 0x1c: invalid BAR (can't size)
>     pci 0000:00:00.0: [Firmware Bug]: reg 0x20: invalid BAR (can't size)
>     pci 0000:00:00.0: [Firmware Bug]: reg 0x24: invalid BAR (can't size)
> 
> The appropriate lspci -v log:
> 
>     00:00.0 Host bridge: Marvell Technology Group Ltd. GT-64120/64120A/64121A System Controller (rev 10)
>             Subsystem: Red Hat, Inc Device 1100
>             Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
>             Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
>             Interrupt: pin A routed to IRQ 0
>             Subsystem: Red Hat, Inc Device 1100
>             Flags: medium devsel
>             Memory at <unassigned> (32-bit, prefetchable) [disabled]
>             Memory at <ignored> (32-bit, prefetchable) [disabled]
>             Memory at <ignored> (32-bit, non-prefetchable) [disabled]
>             Memory at <ignored> (32-bit, non-prefetchable) [disabled]
>             Memory at <ignored> (32-bit, non-prefetchable) [disabled]
>             I/O ports at <ignored> [disabled]
> 
> It looks like qemu-system-mips does not fully emulates GT64120 host
> bridge BARs so skipping host bridge BAR's setup fixes qemu-malta
> problem. But can we skip host bridge BAR's setup for other targets?
> 
> Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
> ---
>  drivers/pci/pci.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 3a0e7a5..7953c55 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -331,6 +331,11 @@ unsigned int pci_scan_bus(struct pci_bus *bus)
>  		pr_debug("%02x:%02x [%04x:%04x]\n", bus->number, dev->devfn,
>  		    dev->vendor, dev->device);
>  
> +		if (class == PCI_CLASS_BRIDGE_HOST) {
> +			pr_debug("skip pci host bridge\n");
> +			continue;
> +		}
> +
>  		switch (hdr_type & 0x7f) {
>  		case PCI_HEADER_TYPE_NORMAL:
>  			if (class == PCI_CLASS_BRIDGE_PCI)
> @@ -391,11 +396,6 @@ unsigned int pci_scan_bus(struct pci_bus *bus)
>  			       bus->number, dev->devfn, dev->vendor, dev->device, class, hdr_type);
>  			continue;
>  		}
> -
> -		if (class == PCI_CLASS_BRIDGE_HOST) {
> -			pr_debug("skip pci host bridge\n");
> -			continue;
> -		}
>  	}
>  
>  	/*