Re: [PATCH] powerpc/pci: Fix the initial value of hose->first_busno

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Fri, 2015-01-30 at 17:48 +0800, Chunhe Lan wrote:
> When use "Intel PRO/1000 PT Quad Port Low Profile Server Adapter"
> card on P5040DS and T1040RDB, 32-bit kernel does not identify this
> card. This card has the four RJ-45 ports.
> 
> The bus range of every pci is "bus-range = <0 0xff>" in dts file.
> So the first bus number of every pci should start from 0, and it
> does not start from next_busno. The next_busno is used to count
> the bus sum of all pci devices. So the value of next_busno is
> accumulated.
> 
> This patch fixes this issue, and "Intel PRO/1000 PT Quad Port Low
> Profile Server Adapter" card can work rightly.

So the logic here was meant the way it is, which is to avoid bus number
overlap between domains due to some old cruft in userspace that didn't
deal with them properly.

It *might* be OK to deprecate that (this is *very* old cruft I'm talking
about such as 2001-era X server) however this isn't clear in your patch
description and it isn't clear either why that breaks your stuff.


> Signed-off-by: Chunhe Lan <Chunhe.Lan@freescale.com>
> ---
>  arch/powerpc/kernel/pci_32.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/pci_32.c b/arch/powerpc/kernel/pci_32.c
> index 432459c..a194685 100644
> --- a/arch/powerpc/kernel/pci_32.c
> +++ b/arch/powerpc/kernel/pci_32.c
> @@ -236,13 +236,13 @@ static int __init pcibios_init(void)
>  
>  	/* Scan all of the recorded PCI controllers.  */
>  	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
> -		if (pci_assign_all_buses)
> -			hose->first_busno = next_busno;
> +		hose->first_busno = 0;
>  		hose->last_busno = 0xff;
>  		pcibios_scan_phb(hose);
>  		pci_bus_add_devices(hose->bus);
>  		if (pci_assign_all_buses || next_busno <= hose->last_busno)
> -			next_busno = hose->last_busno + pcibios_assign_bus_offset;
> +			next_busno += hose->last_busno +
> +					pcibios_assign_bus_offset;
>  	}
>  	pci_bus_count = next_busno;
>