Re: [Linaro-acpi] [PATCH V8 7/9] acpi: Add generic MCFG table handling

On Mon, May 30, 2016 at 05:14:20PM +0200, Tomasz Nowicki wrote:

In order to handle PCI config space regions properly in ACPI, new MCFG interface is defined which does sanity checks on MCFG table and keeps its root pointer. The user is able to lookup MCFG regions based on host bridge root structure and domain:bus_start:bus_end touple. Use pci_mmcfg_late_init old prototype to avoid another function name.

Signed-off-by: Tomasz Nowicki tn@semihalf.com Signed-off-by: Jayachandran C jchandra@broadcom.com

---

drivers/acpi/Kconfig | 3 ++ drivers/acpi/Makefile | 1 + drivers/acpi/pci_mcfg.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pci-acpi.h | 2 ++ include/linux/pci.h | 2 +- 5 files changed, 101 insertions(+), 1 deletion(-) create mode 100644 drivers/acpi/pci_mcfg.c

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig index b7e2e77..f98c328 100644 --- a/drivers/acpi/Kconfig +++ b/drivers/acpi/Kconfig @@ -217,6 +217,9 @@ config ACPI_PROCESSOR_IDLE bool select CPU_IDLE +config ACPI_MCFG

• bool

config ACPI_CPPC_LIB bool depends on ACPI_PROCESSOR diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile index 251ce85..632e81f 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_MCFG) += pci_mcfg.o acpi-y += acpi_lpss.o acpi_apd.o acpi-y += acpi_platform.o acpi-y += acpi_pnp.o diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c new file mode 100644 index 0000000..1847f74 --- /dev/null +++ b/drivers/acpi/pci_mcfg.c @@ -0,0 +1,94 @@ +/*

• • Copyright (C) 2016 Broadcom
• • Author: Jayachandran C jchandra@broadcom.com
• • Copyright (C) 2016 Semihalf
• • Author: Tomasz Nowicki tn@semihalf.com
• • 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.
• */

+#define pr_fmt(fmt) "ACPI: " fmt

+#include <linux/kernel.h> +#include <linux/pci.h> +#include <linux/pci-acpi.h>

+/* Root pointer to the mapped MCFG table */ +static struct acpi_table_mcfg *mcfg_table; +static int mcfg_entries;

+int pci_mcfg_lookup(struct acpi_pci_root *root)

I think this would be better if we passed in the domain and a pointer to the bus range resource and returned the ECAM base address. I don't think we need to be connected to struct acpi_pci_root.

+{

• struct acpi_mcfg_allocation *mptr, *entry = NULL;
• struct resource *bus_res = &root->secondary;
• int i;
• if (mcfg_table) {

• mptr = (struct acpi_mcfg_allocation *) &mcfg_table[1];
  

• for (i = 0; i < mcfg_entries && !entry; i++, mptr++)
  

• 	if (mptr->pci_segment == root->segment &&
  

• 	    mptr->start_bus_number == bus_res->start)
  

• 		entry = mptr;
  

• }
• /* not found, use _CBA if available, else error */
• if (!entry) {

• if (root->mcfg_addr)
  

• 	return root->mcfg_addr;
  

• pr_err("%04x:%pR MCFG lookup failed\n", root->segment, bus_res);
  

• return -ENOENT;
  

• } else if (root->mcfg_addr && entry->address != root->mcfg_addr) {

• pr_warn("%04x:%pR CBA %pa != MCFG %lx, using CBA\n",
  

• 	root->segment, bus_res, &root->mcfg_addr,
  

• 	(unsigned long)entry->address);
  

• return 0;
  

• }

I keep looking at this code, trying to find where we "use _CBA", but I can't find it. Oh, I see, acpi_pci_root_add() calls acpi_pci_root_get_mcfg_addr() (which evaluates _CBA), and sets root->mcfg_addr to the result.

"root->mcfg_addr" is sort of an unfortunate name because "MCFG" is the ACPI table name, we've used "ECAM" for the memory-mapped config space, and this address can come from either the MCFG table or the _CBA method.

In the case where we have both _CBA and an MCFG entry, I think we should prefer _CBA, and I'm not sure it's even worth warning about it. So I think you could simplify this function if you made pci_acpi_setup_ecam_mapping() look like this:

... pci_acpi_setup_ecam_mapping(...) { ... if (!root->mcfg_addr) root->mcfg_addr = pci_mcfg_lookup(root);

if (!root->mcfg_addr) { dev_err(..., "no ECAM region found\n"); return -EINVAL; }

• /* found matching entry, bus range check */
• if (entry->end_bus_number != bus_res->end) {

• resource_size_t bus_end = min_t(resource_size_t,
  

• 			entry->end_bus_number, bus_res->end);
  

• pr_warn("%04x:%pR bus end mismatch, using %02lx\n",
  

• 	root->segment, bus_res, (unsigned long)bus_end);
  

• bus_res->end = bus_end;
  

• }
• if (!root->mcfg_addr)

• root->mcfg_addr = entry->address;
  

Please move the assignment to the caller (I think Lorenzo pointed this out already).

• return 0;

+}

+static __init int pci_mcfg_parse(struct acpi_table_header *header) +{

• if (header->length < sizeof(struct acpi_table_mcfg))

• return -EINVAL;
  

• mcfg_entries = (header->length - sizeof(struct acpi_table_mcfg)) /

• 			sizeof(struct acpi_mcfg_allocation);
  

• if (mcfg_entries == 0) {

• pr_err("MCFG has no entries\n");
  

Include an address here? I'm not really sure either of the messages here is necessary. Users (callers of pci_mcfg_lookup()) will notice if we can't find any ECAM space and will probably complain there, where the message can include more information, e.g., the affected device.

• return -EINVAL;
  

• }
• mcfg_table = (struct acpi_table_mcfg *)header;
• pr_info("MCFG table detected, %d entries\n", mcfg_entries);
• return 0;

+}

+/* Interface called by ACPI - parse and save MCFG table */

I think we save a *pointer* to the MCFG table, not the table itself.

And acpi_table_parse() calls early_acpi_os_unmap_memory() immediately after it calls pci_mcfg_parse(), so I'm doubtful that the pointer remains valid.

+void __init pci_mmcfg_late_init(void) +{

• int err = acpi_table_parse(ACPI_SIG_MCFG, pci_mcfg_parse);
• if (err)

• pr_err("Failed to parse MCFG (%d)\n", err);
  

+} diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h index 89ab057..e0e6dfc 100644 --- a/include/linux/pci-acpi.h +++ b/include/linux/pci-acpi.h @@ -24,6 +24,8 @@ static inline acpi_status pci_acpi_remove_pm_notifier(struct acpi_device *dev) } extern phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle); +extern int pci_mcfg_lookup(struct acpi_pci_root *root);

static inline acpi_handle acpi_find_root_bridge_handle(struct pci_dev *pdev) { struct pci_bus *pbus = pdev->bus; diff --git a/include/linux/pci.h b/include/linux/pci.h index bba4053..9661c85 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1724,7 +1724,7 @@ void pcibios_free_irq(struct pci_dev *dev); extern struct dev_pm_ops pcibios_pm_ops; #endif -#ifdef CONFIG_PCI_MMCONFIG +#if defined(CONFIG_PCI_MMCONFIG) || defined(CONFIG_ACPI_MCFG) void __init pci_mmcfg_early_init(void); void __init pci_mmcfg_late_init(void);

#else

1.9.1