Pieralisi <lorenzo.pieralisi@xxxxxxx> Bcc: Subject: Re: [PATCH v5] PCI: use IDA to manage domain number if not getting it from DT Reply-To: In-Reply-To: <1498523473-157373-1-git-send-email-shawn.lin@xxxxxxxxxxxxxx> [+cc Lorenzo] On Tue, Jun 27, 2017 at 08:31:13AM +0800, Shawn Lin wrote: > If not getting domain number from DT, the domain number will > keep increasing once doing unbind/bind RC drivers. This could > introduce pointless tree view of lspci as shows below: > > -+-[0001:00]---00.0-[01]----00.0 > \-[0000:00]- > > The more test we do, the lengthier it would be. The more serious > issue is that if attaching two hierarchies for two different domains > belonging to two root bridges, so when doing unbind/bind test for one > of them and keep the other, then the domain number would finally > overflow and make the two hierarchies of devices share the some domain > number but actually they shouldn't. So it looks like we need to invent > a new indexing ID mechanism to manage domain number. This patch > introduces idr to achieve our purpose. > > Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> The "use_dt_domains" logic in of_pci_bus_find_domain_nr() is fairly obtuse. I *think*, now that we have pci_scan_root_bus_bridge() due to Lorenzo's excellent work, the time is ripe for moving the domain number from arch-specific places into struct pci_host_bridge. I suspect that will end up simplifying the CONFIG_PCI_DOMAINS vs CONFIG_PCI_DOMAINS_GENERIC situation, and I wonder whether it might enable some simplification of of_pci_bus_find_domain_nr() as well, which in turn, might make *this* patch simpler. This isn't that big a patch to begin with, so I could apply it as-is and we could do more domain cleanup later. It's just that it's intertwined with the PCI_DOMAINS #ifdefs and maybe there's an opportunity to make this story more readable if those are out of the way. Any thoughts? One trivial nit below, which I've already fixed up on my local branch. > --- > > Changes in v5: > - fix Bjorn's comments for v3 as actually I didn't address his comments > for v3 when posted my v4. > v3: https://patchwork.kernel.org/patch/9742003/ > For ACPI case, we never use DT or IDA to get domain numbers and > acpi_pci_bus_find_domain_nr would return the proper value we need > whether _SEG exist or not. For DT or IDA, we hope bridges use one of > them consistently, and this is actually what the pre-existing code > did. So I remove ida_domain now since it complicated the logic of the > code and we could just make use_dt_domains global instead to slightly > achieve our purpose. > > Changes in v4: > - make domain_nr depends on CONFIG_PCI_DOMAINS instead of > CONFIG_PCI_DOMAINS_GENERIC. > > Changes in v3: > - make ida_domain a system-wide property and check it in the code to > combine with use_dt_domains. Also update the comment there. > > Changes in v2: > - add a remove wrapper > - rename use_dt_domains to ida_domain and set this bit > in pci_get_new_domain_nr and test it in the remove wrapper. > > drivers/pci/pci.c | 13 ++++++++++--- > drivers/pci/remove.c | 2 ++ > include/linux/pci.h | 7 +++++-- > 3 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index b58a6b3..9953eaf 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -11,6 +11,7 @@ > #include <linux/kernel.h> > #include <linux/delay.h> > #include <linux/dmi.h> > +#include <linux/idr.h> > #include <linux/init.h> > #include <linux/of.h> > #include <linux/of_pci.h> > @@ -5305,17 +5306,23 @@ static void pci_no_domains(void) > } > > #ifdef CONFIG_PCI_DOMAINS > -static atomic_t __domain_nr = ATOMIC_INIT(-1); > +static DEFINE_IDA(__domain_nr); > > int pci_get_new_domain_nr(void) > { > - return atomic_inc_return(&__domain_nr); > + return ida_simple_get(&__domain_nr, 0, sizeof(u64), GFP_KERNEL); > +} > + > +static int use_dt_domains = -1; > +void pci_put_domain_nr(struct pci_bus *bus) > +{ > + if (acpi_disabled && use_dt_domains != 1) > + ida_simple_remove(&__domain_nr, bus->domain_nr); > } > > #ifdef CONFIG_PCI_DOMAINS_GENERIC > static int of_pci_bus_find_domain_nr(struct device *parent) > { > - static int use_dt_domains = -1; > int domain = -1; > > if (parent) > diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c > index 73a03d3..01dd1b4 100644 > --- a/drivers/pci/remove.c > +++ b/drivers/pci/remove.c > @@ -157,6 +157,8 @@ void pci_remove_root_bus(struct pci_bus *bus) > list_for_each_entry_safe(child, tmp, > &bus->devices, bus_list) > pci_remove_bus_device(child); > + > + pci_put_domain_nr(bus); > pci_remove_bus(bus); > host_bridge->bus = NULL; > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 18cc70a..d6be9596 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -523,7 +523,7 @@ struct pci_bus { > unsigned char primary; /* number of primary bridge */ > unsigned char max_bus_speed; /* enum pci_bus_speed */ > unsigned char cur_bus_speed; /* enum pci_bus_speed */ > -#ifdef CONFIG_PCI_DOMAINS_GENERIC > +#ifdef CONFIG_PCI_DOMAINS > int domain_nr; > #endif > > @@ -1466,11 +1466,14 @@ static inline int pci_enable_ptm(struct pci_dev *dev, u8 *granularity) > #ifdef CONFIG_PCI_DOMAINS > extern int pci_domains_supported; > int pci_get_new_domain_nr(void); > +void pci_put_domain_nr(struct pci_bus *bus); > #else > enum { pci_domains_supported = 0 }; > static inline int pci_domain_nr(struct pci_bus *bus) { return 0; } > static inline int pci_proc_domain(struct pci_bus *bus) { return 0; } > -static inline int pci_get_new_domain_nr(void) { return -ENOSYS; } > +static inline int pci_get_new_domain_nr(void) > +{ return -ENOSYS; } This looks liks a spurious change. > +static inline void pci_put_domain_nr(struct pci_bus *bus) { } > #endif /* CONFIG_PCI_DOMAINS */ > > /* > -- > 1.9.1 > >
