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Message-ID: <20221107230527.GA426221@bhelgaas>
Date: Mon, 7 Nov 2022 17:05:27 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Pali Rohár <pali@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
Marek Behún <marek.behun@....cz>,
Tomasz Nowicki <tn@...ihalf.com>,
Liviu Dudau <Liviu.Dudau@....com>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Assign PCI domain by ida_alloc()
[+cc Tomasz, Liviu since they worked on this code long ago]
On Thu, Jul 14, 2022 at 08:41:30PM +0200, Pali Rohár wrote:
> Replace assignment of PCI domain from atomic_inc_return() to ida_alloc().
>
> Use two IDAs, one for static domain allocations (those which are defined in
> device tree) and second for dynamic allocations (all other).
>
> During removal of root bus / host bridge release also allocated domain id.
> So released id can be reused again, for example in situation when
> dynamically loading and unloading native PCI host bridge drivers.
>
> This change also allows to mix static device tree assignment and dynamic by
> kernel as all static allocations are reserved in dynamic pool.
>
> Signed-off-by: Pali Rohár <pali@...nel.org>
Applied to pci/enumeration for v6.2, thanks!
Using the IDAs makes this look so much nicer than what we had before.
> ---
> Idea of this patch comes from the following discussion:
> https://lore.kernel.org/linux-pci/20210412123936.25555-1-pali@kernel.org/t/#u
>
> Changes in v2:
> * Fix broken compilation
> ---
> drivers/pci/pci.c | 103 +++++++++++++++++++++++++------------------
> drivers/pci/probe.c | 5 +++
> drivers/pci/remove.c | 6 +++
> include/linux/pci.h | 1 +
> 4 files changed, 72 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index cfaf40a540a8..34fdcee6634a 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6762,60 +6762,70 @@ static void pci_no_domains(void)
> }
>
> #ifdef CONFIG_PCI_DOMAINS_GENERIC
> -static atomic_t __domain_nr = ATOMIC_INIT(-1);
> +static DEFINE_IDA(pci_domain_nr_static_ida);
> +static DEFINE_IDA(pci_domain_nr_dynamic_ida);
>
> -static int pci_get_new_domain_nr(void)
> +static void of_pci_reserve_static_domain_nr(void)
> {
> - return atomic_inc_return(&__domain_nr);
> + struct device_node *np;
> + int domain_nr;
> +
> + for_each_node_by_type(np, "pci") {
> + domain_nr = of_get_pci_domain_nr(np);
> + if (domain_nr < 0)
> + continue;
> + /*
> + * Permanently allocate domain_nr in dynamic_ida
> + * to prevent it from dynamic allocation.
> + */
> + ida_alloc_range(&pci_domain_nr_dynamic_ida,
> + domain_nr, domain_nr, GFP_KERNEL);
> + }
> }
>
> static int of_pci_bus_find_domain_nr(struct device *parent)
> {
> - static int use_dt_domains = -1;
> - int domain = -1;
> + static bool static_domains_reserved = false;
> + int domain_nr;
>
> - if (parent)
> - domain = of_get_pci_domain_nr(parent->of_node);
> + /* On the first call scan device tree for static allocations. */
> + if (!static_domains_reserved) {
> + of_pci_reserve_static_domain_nr();
> + static_domains_reserved = true;
> + }
> +
> + if (parent) {
> + /*
> + * If domain is in DT then allocate it in static IDA.
> + * This prevent duplicate static allocations in case
> + * of errors in DT.
> + */
> + domain_nr = of_get_pci_domain_nr(parent->of_node);
> + if (domain_nr >= 0)
> + return ida_alloc_range(&pci_domain_nr_static_ida,
> + domain_nr, domain_nr,
> + GFP_KERNEL);
> + }
>
> /*
> - * 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 was not specified in DT then choose free id from dynamic
> + * allocations. All domain numbers from DT are permanently in dynamic
> + * allocations to prevent assigning them to other DT nodes without
> + * static domain.
> */
> - 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 {
> - if (parent)
> - pr_err("Node %pOF has ", parent->of_node);
> - pr_err("Inconsistent \"linux,pci-domain\" property in DT\n");
> - domain = -1;
> - }
> + return ida_alloc(&pci_domain_nr_dynamic_ida, GFP_KERNEL);
> +}
>
> - return domain;
> +static void of_pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent)
> +{
> + if (bus->domain_nr < 0)
> + return;
> +
> + /* Release domain from ida in which was it allocated. */
> + if (of_get_pci_domain_nr(parent->of_node) == bus->domain_nr)
> + ida_free(&pci_domain_nr_static_ida, bus->domain_nr);
> + else
> + ida_free(&pci_domain_nr_dynamic_ida, bus->domain_nr);
> }
>
> int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
> @@ -6823,6 +6833,13 @@ int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
> return acpi_disabled ? of_pci_bus_find_domain_nr(parent) :
> acpi_pci_bus_find_domain_nr(bus);
> }
> +
> +void pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent)
> +{
> + if (!acpi_disabled)
> + return;
> + of_pci_bus_release_domain_nr(bus, parent);
> +}
> #endif
>
> /**
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 17a969942d37..12092d238403 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -906,6 +906,8 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> else
> bus->domain_nr = bridge->domain_nr;
> + if (bus->domain_nr < 0)
> + goto free;
> #endif
>
> b = pci_find_bus(pci_domain_nr(bus), bridge->busnr);
> @@ -1030,6 +1032,9 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> device_del(&bridge->dev);
>
> free:
> +#ifdef CONFIG_PCI_DOMAINS_GENERIC
> + pci_bus_release_domain_nr(bus, parent);
> +#endif
> kfree(bus);
> return err;
> }
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 4c54c75050dc..0145aef1b930 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -160,6 +160,12 @@ void pci_remove_root_bus(struct pci_bus *bus)
> pci_remove_bus(bus);
> host_bridge->bus = NULL;
>
> +#ifdef CONFIG_PCI_DOMAINS_GENERIC
> + /* Release domain_nr if it was dynamically allocated */
> + if (host_bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
> + pci_bus_release_domain_nr(bus, host_bridge->dev.parent);
> +#endif
> +
> /* remove the host bridge */
> device_del(&host_bridge->dev);
> }
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 81a57b498f22..6c7f27e62bcc 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1723,6 +1723,7 @@ static inline int acpi_pci_bus_find_domain_nr(struct pci_bus *bus)
> { return 0; }
> #endif
> int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent);
> +void pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent);
> #endif
>
> /* Some architectures require additional setup to direct VGA traffic */
> --
> 2.20.1
>
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