linux-kernel - Re: [PATCH v8 19/30] powerpc/pci: Use pci_scan_host

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Date:	Thu, 26 Mar 2015 09:17:10 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Daniel Axtens <dja@...ens.net>
CC:	Liviu Dudau <liviu@...au.co.uk>,
	Rusty Russell <rusty@...tcorp.com.au>,
	<linux-ia64@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
	Marc Zyngier <marc.zyngier@....com>,
	<linux-pci@...r.kernel.org>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	<linuxppc-dev@...ts.ozlabs.org>, <linux-m68k@...ts.linux-m68k.org>,
	Tony Luck <tony.luck@...el.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	<linux-alpha@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	"Russell King" <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Guan Xuetao" <gxt@...c.pku.edu.cn>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 19/30] powerpc/pci: Use pci_scan_host_bridge() for
 simplicity

On 2015/3/26 6:13, Daniel Axtens wrote:
> Hi Yijing,
> 
> I wasn't quite sure I understood your comments, so I was trying to apply
> your patch series and test it, but patch 3 doesn't apply cleanly to
> 4.0-rc5 or master. Can you respin the series?

Hi Daniel,
   Could you pull the series from Bjorn's git tree ? The URL is
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git pci/enumeration-yw8

Thanks!
Yijing.

> 
> Thanks,
> Daniel
> 
> 
>> Hi Daniel, thanks for your review and comments. We want to make a generic pci_host_bridge,
>> which would hold the common host information, for example, pci domain is common info for
>> pci host bridge, this series saved domain in pci_host_bridge, then we no need to
>> extract out domain by pci_bus->sysdata by platform specific pci_domain_nr().
>> Also we store the sysdata in pci_host_bridge, and pci_bus_to_host() is the platform
>> interface, I think use the common interface would be better.
>>
>>>> +
>>>> +	/* Get probe mode and perform scan */
>>>> +	if (hose->dn && ppc_md.pci_probe_mode)
>>>> +		mode = ppc_md.pci_probe_mode(bus);
>>>> +
>>>> +	pr_debug("    probe mode: %d\n", mode);
>>>> +	if (mode == PCI_PROBE_DEVTREE)
>>>> +		of_scan_bus(hose->dn, bus);
>>>> +
>>>> +	if (mode == PCI_PROBE_NORMAL) {
>>>> +		pci_bus_update_busn_res_end(bus, 255);
>>>> +		hose->last_busno = pci_scan_child_bus(bus);
>>>> +		pci_bus_update_busn_res_end(bus, hose->last_busno);
>>>> +	}
>>>> +
>>>> +	return pci_bus_child_max_busnr(bus);
>>>> +}
>>>> +
>>> I'm having trouble convincing myself that this patch covers every
>>> variation within our PCI implementations. In particular, there's a
>>> stanza in of_scan_pci_bridge in kernel/pci_of_scan.c that's almost
>>> identical to this function. Does that implementation need to be cleaned
>>> up and replaced with this function too?
>>>
>>
>> This is a pci_host_bridge_ops hook function, which would be called in
>> PCI core, and after applied this series, we only need to call pci_scan_host_bridge()
>> to scan pci devices, and this function is also extracted from the pcibios_scan_phb(),
>> it's not the redundant code.
>>
>>>
>>>> @@ -1641,9 +1655,9 @@ void pcibios_scan_phb(struct pci_controller *hose)
>>>>  		ppc_md.pcibios_fixup_phb(hose);
>>>>  
>>>>  	/* Configure PCI Express settings */
>>>> -	if (bus && !pci_has_flag(PCI_PROBE_ONLY)) {
>>>> +	if (host->bus && !pci_has_flag(PCI_PROBE_ONLY)) {
>>>>  		struct pci_bus *child;
>>>> -		list_for_each_entry(child, &bus->children, node)
>>>> +		list_for_each_entry(child, &host->bus->children, node)
>>>>  			pcie_bus_configure_settings(child);
>>>>  	}
>>>>  }
>>> Two things: Firstly, the function uses hose throughout, not host.
>>> Secondly, you're not deleting the bus variable: what's the purpose of
>>> this change?
>>
>> host is the common pci_host_bridge which is created by PCI core for pci host bridge driver,
>> the hose is the platform data used in powerpc. The purpose of the patch/series is to simplify
>> pci enumeration interface, and try to reduce the weak functions which were used to setup pci bus/devices
>> during PCI enumeration.
>>
>>>
>>> Regards,
>>> Daniel
>>>
>>
>>
> 


-- 
Thanks!
Yijing

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