Re: [PATCH 15/19] LoongArch: Add PCI controller support

[Huacai Chen <chenhuacai@gmail.com>]

Hi, Arnd,

On Tue, Jul 6, 2021 at 6:17 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Tue, Jul 6, 2021 at 6:18 AM Huacai Chen <chenhuacai@loongson.cn> wrote:
> >
> > Loongson64 based systems are PC-like systems which use PCI/PCIe as its
> > I/O bus, This patch adds the PCI host controller support for LoongArch.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >  arch/loongarch/include/asm/pci.h  | 124 ++++++++++++++++++
> >  arch/loongarch/pci/acpi.c         | 194 ++++++++++++++++++++++++++++
> >  arch/loongarch/pci/mmconfig.c     | 105 +++++++++++++++
> >  arch/loongarch/pci/pci-loongson.c | 130 +++++++++++++++++++
> >  arch/loongarch/pci/pci.c          | 207 ++++++++++++++++++++++++++++++
>
> PCI controller support should generally live in drivers/pci/controller/ and
> get reviewed by the subsystem maintainers.
>
> > +/*
> > + * This file essentially defines the interface between board specific
> > + * PCI code and LoongArch common PCI code. Should potentially put into
> > + * include/asm/pci.h file.
> > + */
> > +
> > +#include <linux/ioport.h>
> > +#include <linux/list.h>
> > +
> > +extern const struct pci_ops *__read_mostly loongarch_pci_ops;
>
> There is already an abstraction for this in the common code, don't add another.
OK, thanks.

>
> > +/*
> > + * Each pci channel is a top-level PCI bus seem by CPU.         A machine  with
> > + * multiple PCI channels may have multiple PCI host controllers or a
> > + * single controller supporting multiple channels.
> > + */
> > +struct pci_controller {
> > +       struct list_head list;
> > +       struct pci_bus *bus;
> > +       struct device_node *of_node;
> > +
> > +       struct pci_ops *pci_ops;
> > +       struct resource *mem_resource;
> > +       unsigned long mem_offset;
> > +       struct resource *io_resource;
> > +       unsigned long io_offset;
> > +       unsigned long io_map_base;
> > +       struct resource *busn_resource;
> > +
> > +       unsigned int node;
> > +       unsigned int index;
> > +       unsigned int need_domain_info;
> > +#ifdef CONFIG_ACPI
> > +       struct acpi_device *companion;
> > +#endif
> > +       phys_addr_t mcfg_addr;
> > +};
> > +
> > +extern void pcibios_add_root_resources(struct list_head *resources);
> > +
> > +extern phys_addr_t mcfg_addr_init(int domain);
> > +
> > +#ifdef CONFIG_PCI_DOMAINS
> > +static inline void set_pci_need_domain_info(struct pci_controller *hose,
> > +                                           int need_domain_info)
> > +{
> > +       hose->need_domain_info = need_domain_info;
> > +}
> > +#endif /* CONFIG_PCI_DOMAINS */
>
> Just use PCI_DOMAINS unconditionally
OK, thanks.

>
> > +
> > +/*
> > + * Can be used to override the logic in pci_scan_bus for skipping
> > + * already-configured bus numbers - to be used for buggy BIOSes
> > + * or architectures with incomplete PCI setup by the loader
> > + */
> > +static inline unsigned int pcibios_assign_all_busses(void)
> > +{
> > +       return 1;
> > +}
>
> Since you use ACPI, the BIOS should be responsible for assigning the
> buses, otherwise the ACPI data may be mismatched with the PCI
> device locations that the kernel sees.
>
> > +#define PCIBIOS_MIN_IO         0
>
> I think this means PCI devices can reuse ports that are reserved
> for ISA devices. Since you claim to support ISA, I think this should
> be 0x1000
OK, thanks.

>
> > +
> > +int raw_pci_read(unsigned int domain, unsigned int bus, unsigned int devfn,
> > +                                               int reg, int len, u32 *val)
> > +{
> > +       struct pci_bus *bus_tmp = pci_find_bus(domain, bus);
> > +
> > +       if (bus_tmp)
> > +               return bus_tmp->ops->read(bus_tmp, devfn, reg, len, val);
> > +       return -EINVAL;
> > +}
> > +
> > +int raw_pci_write(unsigned int domain, unsigned int bus, unsigned int devfn,
> > +                                               int reg, int len, u32 val)
> > +{
> > +       struct pci_bus *bus_tmp = pci_find_bus(domain, bus);
> > +
> > +       if (bus_tmp)
> > +               return bus_tmp->ops->write(bus_tmp, devfn, reg, len, val);
> > +       return -EINVAL;
> > +}
>
> This looks like you copied from arch/arm64. I think the code really
> needs to be generalized more. Maybe move the arm64 implementation
> to drivers/acpi/ so it can be shared with loongarch?
Emmm, this seems like a future story..

Huacai
>
> > +/*
> > + * We need to avoid collisions with `mirrored' VGA ports
> > + * and other strange ISA hardware, so we always want the
> > + * addresses to be allocated in the 0x000-0x0ff region
> > + * modulo 0x400.
> > + *
> > + * Why? Because some silly external IO cards only decode
> > + * the low 10 bits of the IO address. The 0x00-0xff region
> > + * is reserved for motherboard devices that decode all 16
> > + * bits, so it's ok to allocate at, say, 0x2800-0x28ff,
> > + * but we want to try to avoid allocating at 0x2900-0x2bff
> > + * which might have be mirrored at 0x0100-0x03ff..
> > + */
> > +resource_size_t
> > +pcibios_align_resource(void *data, const struct resource *res,
> > +                      resource_size_t size, resource_size_t align)
> > +{
> > +       struct pci_dev *dev = data;
> > +       struct pci_controller *hose = dev->sysdata;
> > +       resource_size_t start = res->start;
> > +
> > +       if (res->flags & IORESOURCE_IO) {
> > +               /* Make sure we start at our min on all hoses */
> > +               if (start < PCIBIOS_MIN_IO + hose->io_resource->start)
> > +                       start = PCIBIOS_MIN_IO + hose->io_resource->start;
> > +
> > +               /*
> > +                * Put everything into 0x00-0xff region modulo 0x400
> > +                */
> > +               if (start & 0x300)
> > +                       start = (start + 0x3ff) & ~0x3ff;
> > +       } else if (res->flags & IORESOURCE_MEM) {
> > +               /* Make sure we start at our min on all hoses */
> > +               if (start < PCIBIOS_MIN_MEM)
> > +                       start = PCIBIOS_MIN_MEM;
> > +       }
> > +
> > +       return start;
> > +}
>
> Same here, please don't add another copy of this function.
>
>
>        Arnd