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Message-ID: <20150302234147.GA11978@google.com>
Date: Mon, 2 Mar 2015 17:41:47 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Yijing Wang <wangyijing@...wei.com>
Cc: Jiang Liu <jiang.liu@...ux.intel.com>, linux-pci@...r.kernel.org,
Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org,
Marc Zyngier <marc.zyngier@....com>,
linux-arm-kernel@...ts.infradead.org,
Russell King <linux@....linux.org.uk>, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Rusty Russell <rusty@...tcorp.com.au>,
Tony Luck <tony.luck@...el.com>, linux-ia64@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Guan Xuetao <gxt@...c.pku.edu.cn>, linux-alpha@...r.kernel.org,
linux-m68k@...ts.linux-m68k.org, Liviu Dudau <liviu@...au.co.uk>,
Arnd Bergmann <arnd@...db.de>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Richard Henderson <rth@...ddle.net>,
Ivan Kokshaysky <ink@...assic.park.msu.ru>,
Matt Turner <mattst88@...il.com>, sparclinux@...r.kernel.org
Subject: Re: [PATCH v4 01/30] PCI: Rip out pci_bus_add_devices() from
pci_scan_bus()
On Thu, Feb 26, 2015 at 04:11:55PM +0800, Yijing Wang wrote:
> Pci_bus_add_devices() should not be placed in pci_scan_bus().
> Now pci device will be added to driver core once its
> creation. All things left in pci_bus_add_devices() are
> driver attachment and other trivial sysfs things.
> Pci_scan_bus() should be the function responsible for
> scanning PCI devices, not including driver attachment.
> Other, some callers(m68k,unicore32,alpha) of pci_scan_bus()
> will call pci_bus_size_bridges() and pci_bus_assign_resources()
> after pci_scan_bus().
>
> E.g.
> In m68k
> mcf_pci_init()
> pci_scan_bus()
> ...
> pci_bus_add_devices() --- try to attach driver
> pci_fixup_irqs()
> pci_bus_size_bridges()
> pci_bus_assign_resources()
>
> Above code flow make pci scan logic obscure, resources should
> be assigned correctly before attaching driver. Because
> pci_scan_bus() mostly be called in system boot path, when
> before drivers are loaded(in module_init), so no pci scan
> issues will occur. Most pci_scan_bus() callers additionally
> call pci_bus_size_bridges() and pci_bus_assign_resources()
> after pci_scan_bus(), we could rip out pci_bus_add_devices()
> for better code readability. After applied this patch,
> pci_scan_bus() should be used like:
>
> pci_scan_bus() (mandatory)
> pci_fixup_irqs() (optional)
> pci_bus_size_bridges() (optional)
> pci_pci_bus_assign_resources() (optional)
> pci_bus_add_devices() (mandatory)
>
> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: Geert Uytterhoeven <geert@...ux-m68k.org>
> CC: Guan Xuetao <gxt@...c.pku.edu.cn>
> CC: Richard Henderson <rth@...ddle.net>
> CC: Ivan Kokshaysky <ink@...assic.park.msu.ru>
> CC: Matt Turner <mattst88@...il.com>
> CC: linux-alpha@...r.kernel.org
> CC: linux-m68k@...ts.linux-m68k.org
> CC: sparclinux@...r.kernel.org
> ---
> arch/alpha/kernel/sys_nautilus.c | 1 +
> arch/m68k/coldfire/pci.c | 1 +
> arch/sparc/kernel/pcic.c | 2 ++
> arch/unicore32/kernel/pci.c | 11 +++--------
> drivers/pci/hotplug/ibmphp_core.c | 6 ++++--
> drivers/pci/probe.c | 1 -
> 6 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/arch/alpha/kernel/sys_nautilus.c b/arch/alpha/kernel/sys_nautilus.c
> index 837c0fa..4ae4a40 100644
> --- a/arch/alpha/kernel/sys_nautilus.c
> +++ b/arch/alpha/kernel/sys_nautilus.c
> @@ -253,6 +253,7 @@ nautilus_init_pci(void)
> for the root bus, so just clear it. */
> bus->self = NULL;
> pci_fixup_irqs(alpha_mv.pci_swizzle, alpha_mv.pci_map_irq);
> + pci_bus_add_devices(bus);
> }
>
> /*
> diff --git a/arch/m68k/coldfire/pci.c b/arch/m68k/coldfire/pci.c
> index df96792..d45f087 100644
> --- a/arch/m68k/coldfire/pci.c
> +++ b/arch/m68k/coldfire/pci.c
> @@ -319,6 +319,7 @@ static int __init mcf_pci_init(void)
> pci_fixup_irqs(pci_common_swizzle, mcf_pci_map_irq);
> pci_bus_size_bridges(rootbus);
> pci_bus_assign_resources(rootbus);
> + pci_bus_add_devices(rootbus);
> return 0;
> }
>
> diff --git a/arch/sparc/kernel/pcic.c b/arch/sparc/kernel/pcic.c
> index 6cc78c2..7a82fe2 100644
> --- a/arch/sparc/kernel/pcic.c
> +++ b/arch/sparc/kernel/pcic.c
> @@ -391,6 +391,8 @@ static void __init pcic_pbm_scan_bus(struct linux_pcic *pcic)
> struct linux_pbm_info *pbm = &pcic->pbm;
>
> pbm->pci_bus = pci_scan_bus(pbm->pci_first_busno, &pcic_ops, pbm);
> + if (pbm->pci_bus)
> + pci_bus_add_devices(pbm->pci_bus);
> #if 0 /* deadwood transplanted from sparc64 */
> pci_fill_in_pbm_cookies(pbm->pci_bus, pbm, pbm->prom_node);
> pci_record_assignments(pbm, pbm->pci_bus);
This is correct, but it should look like this instead:
if (!pbm->pci_bus)
return;
#if 0 /* deadwood ... */
...
#endif
pci_bus_add_devices(pbm->pci_bus);
}
That way the mainline code is the normal path, and pci_bus_add_devices() is
in the correct place even if the "deadwood" code is resurrected.
> diff --git a/arch/unicore32/kernel/pci.c b/arch/unicore32/kernel/pci.c
> index 374a055..3d82024 100644
> --- a/arch/unicore32/kernel/pci.c
> +++ b/arch/unicore32/kernel/pci.c
> @@ -266,17 +266,12 @@ static int __init pci_common_init(void)
> pci_fixup_irqs(pci_common_swizzle, pci_puv3_map_irq);
>
> if (!pci_has_flag(PCI_PROBE_ONLY)) {
> - /*
> - * Size the bridge windows.
> - */
> + /* Size the bridge windows. */
> pci_bus_size_bridges(puv3_bus);
> -
> - /*
> - * Assign resources.
> - */
> + /* Assign resources. */
> pci_bus_assign_resources(puv3_bus);
> }
> -
> + pci_bus_add_devices(puv3_bus);
> return 0;
> }
> subsys_initcall(pci_common_init);
> diff --git a/drivers/pci/hotplug/ibmphp_core.c b/drivers/pci/hotplug/ibmphp_core.c
> index 96c5c72..86e3bfd 100644
> --- a/drivers/pci/hotplug/ibmphp_core.c
> +++ b/drivers/pci/hotplug/ibmphp_core.c
> @@ -738,7 +738,7 @@ static void ibm_unconfigure_device(struct pci_func *func)
> */
> static u8 bus_structure_fixup(u8 busno)
> {
> - struct pci_bus *bus;
> + struct pci_bus *bus, *b;
> struct pci_dev *dev;
> u16 l;
>
> @@ -765,7 +765,9 @@ static u8 bus_structure_fixup(u8 busno)
> (l != 0x0000) && (l != 0xffff)) {
> debug("%s - Inside bus_structure_fixup()\n",
> __func__);
> - pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
> + b = pci_scan_bus(busno, ibmphp_pci_bus->ops, NULL);
> + if (b)
> + pci_bus_add_devices(b);
Use this:
if (!b)
continue;
pci_bus_add_devices(b);
for the same reason as above.
> break;
> }
> }
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 8d2f400..88604f2 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2123,7 +2123,6 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
> b = pci_create_root_bus(NULL, bus, ops, sysdata, &resources);
> if (b) {
> pci_scan_child_bus(b);
> - pci_bus_add_devices(b);
> } else {
> pci_free_resource_list(&resources);
> }
> --
> 1.7.1
>
--
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