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

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Message-ID: <551266DE.3030609@huawei.com>
Date:	Wed, 25 Mar 2015 15:42:22 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Daniel Axtens <dja@...ens.net>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>, <linux-ia64@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, Guan Xuetao <gxt@...c.pku.edu.cn>,
	Russell King <linux@....linux.org.uk>, <x86@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Arnd Bergmann <arnd@...db.de>,
	Marc Zyngier <marc.zyngier@....com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	<linux-m68k@...ts.linux-m68k.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Liviu Dudau <liviu@...au.co.uk>,
	Tony Luck <tony.luck@...el.com>,
	<linux-kernel@...r.kernel.org>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	<linux-alpha@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v8 19/30] powerpc/pci: Use pci_scan_host_bridge() for
 simplicity

On 2015/3/25 7:58, Daniel Axtens wrote:
> On Tue, 2015-03-24 at 11:34 +0800, Yijing Wang wrote:
>> Now we could use pci_scan_host_bridge() to scan
>> pci buses, provide powerpc specific pci_host_bridge_ops.
>>
>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> CC: linuxppc-dev@...ts.ozlabs.org
>> ---
>>  arch/powerpc/kernel/pci-common.c |   60 +++++++++++++++++++++++--------------
>>  1 files changed, 37 insertions(+), 23 deletions(-)
> 
>> diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
>> index 2c58200..e2b50a2 100644
>> --- a/arch/powerpc/kernel/pci-common.c
>> +++ b/arch/powerpc/kernel/pci-common.c
>> @@ -773,6 +773,29 @@ void pcibios_set_root_bus_speed(struct pci_host_bridge *bridge)
>>  		return ppc_md.pcibios_set_root_bus_speed(bridge);
>>  }
>>  
>> +static int pci_host_scan_bus(struct pci_host_bridge *host)
>> +{
>> +	int mode = PCI_PROBE_NORMAL;
>> +	struct pci_bus *bus = host->bus;
>> +	struct pci_controller *hose = dev_get_drvdata(&host->dev);
> Is there any reason this isn't *hose = pci_bus_to_host(bus)?

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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