Re: [RFC PATCH v2] drivers: pci: move PCI domain assignment to generic PCI code

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

Hi Bjorn,

On Thu, Nov 20, 2014 at 10:54:49PM +0000, Bjorn Helgaas wrote:
> On Mon, Nov 10, 2014 at 04:41:46PM +0000, Lorenzo Pieralisi wrote:
> > The current logic used for PCI domain assignment in arm64
> > pci_bus_assign_domain_nr() is flawed in that, depending on the host
> > controllers configuration for a platform and the respective initialization
> > sequence, core code may end up allocating PCI domain numbers from both DT and
> > the core code generic domain counter, which would result in PCI domain
> > allocation aliases/errors.
> > 
> > This patch fixes the logic behind the PCI domain number assignment and
> > moves the resulting code to generic PCI core code so that the same domain
> > allocation logic is used on all platforms selecting
> > 
> > CONFIG_PCI_DOMAINS_GENERIC
> > 
> > instead of resorting to an arch specific implementation that might end up
> > duplicating the PCI domain assignment logic wrongly.
> > 
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Liviu Dudau <liviu.dudau@arm.com>
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> 
> Applied with Liviu and Arnd's acks to pci/domain for v3.19, thanks.
> 
> It doesn't matter whether I'm in the to: or cc: list.  The important thing
> is that it appears on the linux-pci list, because I use patchwork as my
> to-do list, and patchwork only vacuums up stuff from linux-pci.

This patch has not been merged last cycle and it is a prerequisite for
the ARM pcibios domain code removal patchset you merged in your pci/domain
branch. Please consider pulling it there so that the ARM pcibios domain
removal patchset can be based correctly on top of this patch, at the
moment it can't compile (see kbuild test report).

Thanks,
Lorenzo

> > ---
> > v1 => v2:
> > 
> > - Moved generic pci_bus_assign_domain_nr() code to PCI core instead of
> >   adding an OF layer API
> > - Updated commit log and code comments
> > 
> >  arch/arm64/kernel/pci.c | 22 ----------------------
> >  drivers/pci/pci.c       | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 50 insertions(+), 22 deletions(-)
> > 
> > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> > index ce5836c..6f93c24 100644
> > --- a/arch/arm64/kernel/pci.c
> > +++ b/arch/arm64/kernel/pci.c
> > @@ -46,25 +46,3 @@ int pcibios_add_device(struct pci_dev *dev)
> >  
> >  	return 0;
> >  }
> > -
> > -
> > -#ifdef CONFIG_PCI_DOMAINS_GENERIC
> > -static bool dt_domain_found = false;
> > -
> > -void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> > -{
> > -	int domain = of_get_pci_domain_nr(parent->of_node);
> > -
> > -	if (domain >= 0) {
> > -		dt_domain_found = true;
> > -	} else if (dt_domain_found == true) {
> > -		dev_err(parent, "Node %s is missing \"linux,pci-domain\" property in DT\n",
> > -			parent->of_node->full_name);
> > -		return;
> > -	} else {
> > -		domain = pci_get_new_domain_nr();
> > -	}
> > -
> > -	bus->domain_nr = domain;
> > -}
> > -#endif
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 625a4ac..2279414 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -10,6 +10,8 @@
> >  #include <linux/kernel.h>
> >  #include <linux/delay.h>
> >  #include <linux/init.h>
> > +#include <linux/of.h>
> > +#include <linux/of_pci.h>
> >  #include <linux/pci.h>
> >  #include <linux/pm.h>
> >  #include <linux/slab.h>
> > @@ -4447,6 +4449,54 @@ int pci_get_new_domain_nr(void)
> >  {
> >  	return atomic_inc_return(&__domain_nr);
> >  }
> > +
> > +#ifdef CONFIG_PCI_DOMAINS_GENERIC
> > +
> > +void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> > +{
> > +	static int use_dt_domains = -1;
> > +	int domain = of_get_pci_domain_nr(parent->of_node);
> > +
> > +	/*
> > +	 * Check DT domain and use_dt_domains values.
> > +	 *
> > +	 * If DT domain property is valid (domain >= 0) and
> > +	 * use_dt_domains != 0, the DT assignment is valid since this means
> > +	 * we have not previously allocated a domain number by using
> > +	 * pci_get_new_domain_nr(); we should also update use_dt_domains to
> > +	 * 1, to indicate that we have just assigned a domain number from
> > +	 * DT.
> > +	 *
> > +	 * If DT domain property value is not valid (ie domain < 0), and we
> > +	 * have not previously assigned a domain number from DT
> > +	 * (use_dt_domains != 1) we should assign a domain number by
> > +	 * using the:
> > +	 *
> > +	 * pci_get_new_domain_nr()
> > +	 *
> > +	 * API and update the use_dt_domains value to keep track of method we
> > +	 * are using to assign domain numbers (use_dt_domains = 0).
> > +	 *
> > +	 * All other combinations imply we have a platform that is trying
> > +	 * to mix domain numbers obtained from DT and pci_get_new_domain_nr(),
> > +	 * which is a recipe for domain mishandling and it is prevented by
> > +	 * invalidating the domain value (domain = -1) and printing a
> > +	 * corresponding error.
> > +	 */
> > +	if (domain >= 0 && use_dt_domains) {
> > +		use_dt_domains = 1;
> > +	} else if (domain < 0 && use_dt_domains != 1) {
> > +		use_dt_domains = 0;
> > +		domain = pci_get_new_domain_nr();
> > +	} else {
> > +		dev_err(parent, "Node %s has inconsistent \"linux,pci-domain\" property in DT\n",
> > +			parent->of_node->full_name);
> > +		domain = -1;
> > +	}
> > +
> > +	bus->domain_nr = domain;
> > +}
> > +#endif
> >  #endif
> >  
> >  /**
> > -- 
> > 2.1.2
> > 
>