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

[Yijing Wang <wangyijing@huawei.com>]

Hi Lorenzo,
   You should send this to Bjorn instead of cc. Other, why put the OF related
function in PCI core. Why not move it in drivers/of/of_pci.c ?

On 2014/11/11 0:41, 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>
> ---
> 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
>  
>  /**
> 


-- 
Thanks!
Yijing