Re: [PATCH V6 09/13] pci, acpi: Support for ACPI based generic PCI host controller

Tomasz Nowicki
2016-05-02T11:03:57Z

On 04/28/2016 11:48 PM, Bjorn Helgaas wrote:
> Hey, I really kind of like this. I think this might work out well.
>
> On Fri, Apr 15, 2016 at 07:06:44PM +0200, Tomasz Nowicki wrote:
>> This patch is going to implement generic PCI host controller for
>> ACPI world, similar to what pci-host-generic.c driver does for DT world.
>>
>> All such drivers, which we have seen so far, were implemented within
>> arch/ directory since they had some arch assumptions (x86 and ia64).
>> However, they all are doing similar thing, so it makes sense to find
>> some common code and abstract it into the generic driver.
>>
>> In order to handle PCI config space regions properly, we define new
>> MCFG interface which parses MCFG table and keep its entries
>> in a list. New pci_mcfg_init call is defined so that we do not depend
>> on PCI_MMCONFIG. Regions are not mapped until host bridge ask for it.
>>
>> The implementation of pci_acpi_scan_root() looks up the saved MCFG entries
>> and sets up a new mapping. Generic PCI functions are used for
>> accessing config space. Driver selects PCI_GENERIC_ECAM and uses functions
>> from drivers/pci/ecam.h to create and access ECAM mappings.
>>
>> As mentioned in Kconfig help section, ACPI_PCI_HOST_GENERIC choice
>> should be made on a per-architecture basis.
>>
>> This patch is heavily based on the updated version from Jayachandran C:
>> https://lkml.org/lkml/2016/4/11/908
>> git: https://github.com/jchandra-brcm/linux/ (arm64-acpi-pci-v3)
>>
>> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
>> Signed-off-by: Jayachandran C <jchandra@broadcom.com>
>> ---
>> drivers/acpi/Kconfig | 8 ++
>> drivers/acpi/Makefile | 1 +
>> drivers/acpi/bus.c | 1 +
>> drivers/acpi/pci_gen_host.c | 231 ++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/pci.h | 6 ++
>> 5 files changed, 247 insertions(+)
>> create mode 100644 drivers/acpi/pci_gen_host.c
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index 183ffa3..70272c5 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -346,6 +346,14 @@ config ACPI_PCI_SLOT
>> i.e., segment/bus/device/function tuples, with physical slots in
>> the system. If you are unsure, say N.
>>
>> +config ACPI_PCI_HOST_GENERIC
>> + bool
>> + select PCI_GENERIC_ECAM
>> + help
>> + Select this config option from the architecture Kconfig,
>> + if it is preferred to enable ACPI PCI host controller driver which
>> + has no arch-specific assumptions.
>> +
>> config X86_PM_TIMER
>> bool "Power Management Timer Support" if EXPERT
>> depends on X86
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index 81e5cbc..b12fa64 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -40,6 +40,7 @@ acpi-$(CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC) += processor_pdc.o
>> acpi-y += ec.o
>> acpi-$(CONFIG_ACPI_DOCK) += dock.o
>> acpi-y += pci_root.o pci_link.o pci_irq.o
>> +obj-$(CONFIG_ACPI_PCI_HOST_GENERIC) += pci_gen_host.o
> Maybe "pci_root_generic.c" so it shows up next to and is obviously
> related to pci_root.c?

Yes, this is good idea.

>
>> acpi-y += acpi_lpss.o acpi_apd.o
>> acpi-y += acpi_platform.o
>> acpi-y += acpi_pnp.o
>> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
>> index c068c82..803a1d7 100644
>> --- a/drivers/acpi/bus.c
>> +++ b/drivers/acpi/bus.c
>> @@ -1107,6 +1107,7 @@ static int __init acpi_init(void)
>> }
>>
>> pci_mmcfg_late_init();
>> + pci_mcfg_init();
>> acpi_scan_init();
>> acpi_ec_init();
>> acpi_debugfs_init();
>> diff --git a/drivers/acpi/pci_gen_host.c b/drivers/acpi/pci_gen_host.c
>> new file mode 100644
>> index 0000000..fd360b5
>> --- /dev/null
>> +++ b/drivers/acpi/pci_gen_host.c
>> @@ -0,0 +1,231 @@
>> +/*
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License, version 2, as
>> + * published by the Free Software Foundation (the "GPL").
>> + *
>> + * This program is distributed in the hope that it will be useful, but
>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>> + * General Public License version 2 (GPLv2) for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * version 2 (GPLv2) along with this source code.
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/pci.h>
>> +#include <linux/pci-acpi.h>
>> +#include <linux/sfi_acpi.h>
>> +#include <linux/slab.h>
>> +
>> +#include "../pci/ecam.h"
>> +
>> +#define PREFIX "ACPI: "
>> +
>> +/* Structure to hold entries from the MCFG table */
>> +struct mcfg_entry {
>> + struct list_head list;
>> + phys_addr_t addr;
>> + u16 segment;
>> + u8 bus_start;
>> + u8 bus_end;
>> +};
>> +
>> +/* List to save mcfg entries */
>> +static LIST_HEAD(pci_mcfg_list);
>> +static DEFINE_MUTEX(pci_mcfg_lock);
>> +
>> +/* ACPI info for generic ACPI PCI controller */
>> +struct acpi_pci_generic_root_info {
>> + struct acpi_pci_root_info common;
>> + struct pci_config_window *cfg; /* config space mapping */
>> +};
>> +
>> +/* Find the entry in mcfg list which contains range bus_start */
>> +static struct mcfg_entry *pci_mcfg_lookup(u16 seg, u8 bus_start)
>> +{
>> + struct mcfg_entry *e;
>> +
>> + list_for_each_entry(e, &pci_mcfg_list, list) {
>> + if (e->segment == seg &&
>> + e->bus_start <= bus_start && bus_start <= e->bus_end)
>> + return e;
>> + }
>> +
>> + return NULL;
>> +}
> Can you put the MCFG parsing, caching, and searching in a different
> file, e.g., drivers/acpi/pci_mcfg.c?
I will.
>
>> +/*
>> + * Lookup the bus range for the domain in MCFG, and set up config space
>> + * mapping.
>> + */
>> +static int pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root,
>> + struct acpi_pci_generic_root_info *ri)
>> +{
>> + u16 seg = root->segment;
>> + u8 bus_start = root->secondary.start;
>> + u8 bus_end = root->secondary.end;
>> + struct pci_config_window *cfg;
>> + struct mcfg_entry *e;
>> + phys_addr_t addr;
>> + int err = 0;
>> +
>> + mutex_lock(&pci_mcfg_lock);
> What does this lock protect? The pci_mcfg_list should already be
> initialized by the time we get there, and it should be immutable for
> the life of the system.
Right, lock is useless.
> In fact, I would prefer if we could just
> search the static table itself whenever we need it rather than caching
> it in our own list. But I don't think we can easily do that because
> acpi_table_parse() is __init.

It is doable. We can implement our MCFG __init parsing handle to do
necessary sanity checks and then store MCFG table root pointer in
pci_mcfg.c. Then lookup call would use that pointer to traverse
available entries on demand.

>
>> + e = pci_mcfg_lookup(seg, bus_start);
> I would argue that we should check for _CBA first, and fall back to
> MCFG if _CBA doesn't exist.
Agree.
>
>> + if (!e) {
>> + addr = acpi_pci_root_get_mcfg_addr(root->device->handle);
> IMO, acpi_pci_root_get_mcfg_addr() is misnamed. It should be
> acpi_pci_config_base_addr() or similar. It definitely is not related
> to MCFG. Not your fault, obviously.
>
>> + if (addr == 0) {
>> + pr_err(PREFIX"%04x:%02x-%02x bus range error\n",
>> + seg, bus_start, bus_end);
>> + err = -ENOENT;
>> + goto err_out;
>> + }
>> + } else {
>> + if (bus_start != e->bus_start) {
>> + pr_err("%04x:%02x-%02x bus range mismatch %02x\n",
>> + seg, bus_start, bus_end, e->bus_start);
>> + err = -EINVAL;
>> + goto err_out;
>> + } else if (bus_end != e->bus_end) {
>> + pr_warn("%04x:%02x-%02x bus end mismatch %02x\n",
>> + seg, bus_start, bus_end, e->bus_end);
>> + bus_end = min(bus_end, e->bus_end);
>> + }
>> + addr = e->addr;
>> + }
> I really don't think you need a lock around this, so you can factor
> out the address lookup into something like:
>
> addr = acpi_pci_config_base_addr(...);
> if (addr)
> return addr;
>
> return acpi_pci_mcfg_lookup(seg, busn_res);
>
> You can check inside acpi_pci_mcfg_lookup() to make sure the entry you
> find covers the entire [busn_res.start-busn_res.end] range and return
> failure if it doesn't. At this point, I'm not sure it's worth it to
> truncate the host bridge bus range to match something we find in MCFG.
>
> If the MCFG entry covers *more* than the host bridge range from _CRS,
> that's fine.
Makes sense for me.

> In any case, we have to be careful with the start address,
> because the MCFG start address is always based on bus 0, but I think
> pci_generic_ecam_create() expects the start address based on the
> bus_start you pass to it.

We will have a look how to fix this.
>
>> +
>> + cfg = pci_generic_ecam_create(&root->device->dev, addr, bus_start,
>> + bus_end, &pci_generic_ecam_default_ops);
>> + if (IS_ERR(cfg)) {
>> + err = PTR_ERR(cfg);
>> + pr_err("%04x:%02x-%02x error %d mapping CAM\n", seg,
>> + bus_start, bus_end, err);
>> + goto err_out;
>> + }
>> +
>> + cfg->domain = seg;
>> + ri->cfg = cfg;
>> +err_out:
>> + mutex_unlock(&pci_mcfg_lock);
>> + return err;
>> +}
>> +
>> +/* release_info: free resrouces allocated by init_info */
>> +static void pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
>> +{
>> + struct acpi_pci_generic_root_info *ri;
>> +
>> + ri = container_of(ci, struct acpi_pci_generic_root_info, common);
>> + pci_generic_ecam_free(ri->cfg);
>> + kfree(ri);
>> +}
>> +
>> +static struct acpi_pci_root_ops acpi_pci_root_ops = {
>> + .release_info = pci_acpi_generic_release_info,
>> +};
>> +
>> +/* Interface called from ACPI code to setup PCI host controller */
>> +struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
>> +{
>> + int node = acpi_get_node(root->device->handle);
>> + struct acpi_pci_generic_root_info *ri;
>> + struct pci_bus *bus, *child;
>> + int err;
>> +
>> + ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
>> + if (!ri)
>> + return NULL;
>> +
>> + err = pci_acpi_setup_ecam_mapping(root, ri);
>> + if (err)
>> + return NULL;
>> +
>> + acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
>> + bus = acpi_pci_root_create(root, &acpi_pci_root_ops, &ri->common,
>> + ri->cfg);
>> + if (!bus)
>> + return NULL;
>> +
>> + pci_bus_size_bridges(bus);
>> + pci_bus_assign_resources(bus);
>> +
>> + list_for_each_entry(child, &bus->children, node)
>> + pcie_bus_configure_settings(child);
>> +
>> + return bus;
>> +}
>> +
>> +/* handle MCFG table entries */
>> +static __init int pci_mcfg_parse(struct acpi_table_header *header)
>> +{
>> + struct acpi_table_mcfg *mcfg;
>> + struct acpi_mcfg_allocation *mptr;
>> + struct mcfg_entry *e, *arr;
>> + int i, n;
>> +
>> + if (!header)
>> + return -EINVAL;
>> +
>> + mcfg = (struct acpi_table_mcfg *)header;
>> + mptr = (struct acpi_mcfg_allocation *) &mcfg[1];
>> + n = (header->length - sizeof(*mcfg)) / sizeof(*mptr);
>> + if (n <= 0 || n > 255) {
>> + pr_err(PREFIX " MCFG has incorrect entries (%d).\n", n);
>> + return -EINVAL;
>> + }
>> +
>> + arr = kcalloc(n, sizeof(*arr), GFP_KERNEL);
>> + if (!arr)
>> + return -ENOMEM;
>> +
>> + for (i = 0, e = arr; i < n; i++, mptr++, e++) {
>> + e->segment = mptr->pci_segment;
>> + e->addr = mptr->address;
>> + e->bus_start = mptr->start_bus_number;
>> + e->bus_end = mptr->end_bus_number;
>> + list_add(&e->list, &pci_mcfg_list);
>> + pr_info(PREFIX
>> + "MCFG entry for domain %04x [bus %02x-%02x] (base %pa)\n",
>> + e->segment, e->bus_start, e->bus_end, &e->addr);
> Ah, this is information similar to what I suggested we might print in
> pci_generic_ecam_create(). Could go either way, but personally I
> think I'd put it in pci_generic_ecam_create() instead, because then we
> only print the info we're actually using. And I think it'd be nice to
> have the actual MMIO resource ("[mem 0x...-0x...]") instead of just
> the base.

Giving above that I will drop MCFG entries cache, this will be printed
in pci_generic_ecam_create, as you suggested.
>
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/* Interface called by ACPI - parse and save MCFG table */
>> +void __init pci_mcfg_init(void)
>> +{
>> + int err = acpi_table_parse(ACPI_SIG_MCFG, pci_mcfg_parse);
>> + if (err)
>> + pr_err(PREFIX "Failed to parse MCFG (%d)\n", err);
>> + else if (list_empty(&pci_mcfg_list))
>> + pr_info(PREFIX "No valid entries in MCFG table.\n");
>> + else {
>> + struct mcfg_entry *e;
>> + int i = 0;
>> + list_for_each_entry(e, &pci_mcfg_list, list)
>> + i++;
>> + pr_info(PREFIX "MCFG table loaded, %d entries\n", i);
>> + }
>> +}
>> +
>> +/* Raw operations, works only for MCFG entries with an associated bus */
> Can you elaborate a little on the connection with MCFG? I don't quite
> see how they're related. Obviously the device has to be on a bus
> we've already enumerated and assigned bus->ops for, but it seems like
> we don't really know or care what bus->ops actually is. Given that
> these are in this file, acpi_pci_root_ops is the only possibility,
> since that's what we pass to acpi_pci_root_create(), but it doesn't
> seem worth mentioning specifically in a comment.

Yes, you are right. I will drop this comment.

>
>> +int raw_pci_read(unsigned int domain, unsigned int busn, unsigned int devfn,
>> + int reg, int len, u32 *val)
>> +{
>> + struct pci_bus *bus = pci_find_bus(domain, busn);
>> +
>> + if (!bus)
>> + return PCIBIOS_DEVICE_NOT_FOUND;
>> + return bus->ops->read(bus, devfn, reg, len, val);
>> +}
>> +
>> +int raw_pci_write(unsigned int domain, unsigned int busn, unsigned int devfn,
>> + int reg, int len, u32 val)
>> +{
>> + struct pci_bus *bus = pci_find_bus(domain, busn);
>> +
>> + if (!bus)
>> + return PCIBIOS_DEVICE_NOT_FOUND;
>> + return bus->ops->write(bus, devfn, reg, len, val);
>> +}
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index df1f33d..c0422ea 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -1729,6 +1729,12 @@ static inline void pci_mmcfg_early_init(void) { }
>> static inline void pci_mmcfg_late_init(void) { }
>> #endif
>>
>> +#ifdef CONFIG_ACPI_PCI_HOST_GENERIC
>> +void __init pci_mcfg_init(void);
>> +#else
>> +static inline void pci_mcfg_init(void) { return; }
>> +#endif
>> +
>> int pci_ext_cfg_avail(void);
>>
>> void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar);
>> --
>> 1.9.1
>>
>> --
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Thanks,
Tomasz