Date:	Wed, 15 Jun 2016 15:29:26 +0200
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	marc.zyngier@....com, tglx@...utronix.de, jason@...edaemon.net,
	rjw@...ysocki.net, bhelgaas@...gle.com,
	robert.richter@...iumnetworks.com, shijie.huang@....com,
	Suravee.Suthikulpanit@....com, hanjun.guo@...aro.org,
	al.stone@...aro.org, mw@...ihalf.com, graeme.gregory@...aro.org,
	Catalin.Marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, ddaney.cavm@...il.com,
	okaya@...eaurora.org, andrea.gallo@...aro.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH V6 1/7] ACPI: I/O Remapping Table (IORT) initial support

On 15.06.2016 13:04, Lorenzo Pieralisi wrote:
> On Mon, Jun 13, 2016 at 04:41:07PM +0200, Tomasz Nowicki wrote:
>> IORT shows representation of IO topology for ARM based systems.
>> It describes how various components are connected together on
>> parent-child basis e.g. PCI RC -> SMMU -> ITS. Also see IORT spec.
>>
>> Initial support allows to:
>> - register ITS MSI chip along with ITS translation ID and domain token
>> - deregister ITS MSI chip based on ITS translation ID
>> - find registered domain token based on ITS translation ID
>> - map MSI RID for a device
>> - find domain token for a device
>>
>> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
>> ---
>>   drivers/acpi/Kconfig  |   3 +
>>   drivers/acpi/Makefile |   1 +
>>   drivers/acpi/iort.c   | 386 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/iort.h  |  38 +++++
>>   4 files changed, 428 insertions(+)
>>   create mode 100644 drivers/acpi/iort.c
>>   create mode 100644 include/linux/iort.h
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index f98c328..111dd50 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -57,6 +57,9 @@ config ACPI_SYSTEM_POWER_STATES_SUPPORT
>>   config ACPI_CCA_REQUIRED
>>   	bool
>>
>> +config IORT_TABLE
>> +	bool
>> +
>>   config ACPI_DEBUGGER
>>   	bool "AML debugger interface"
>>   	select ACPI_DEBUG
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index 632e81f..0390f27 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -83,6 +83,7 @@ obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
>>   obj-$(CONFIG_ACPI_BGRT)		+= bgrt.o
>>   obj-$(CONFIG_ACPI_CPPC_LIB)	+= cppc_acpi.o
>>   obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o
>> +obj-$(CONFIG_IORT_TABLE) 	+= iort.o
>>
>>   # processor has its own "processor." module_param namespace
>>   processor-y			:= processor_driver.o
>> diff --git a/drivers/acpi/iort.c b/drivers/acpi/iort.c
>> new file mode 100644
>> index 0000000..5bccbc8
>> --- /dev/null
>> +++ b/drivers/acpi/iort.c
>> @@ -0,0 +1,386 @@
>> +/*
>> + * Copyright (C) 2016, Semihalf
>> + *	Author: Tomasz Nowicki <tn@...ihalf.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope 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 for
>> + * more details.
>> + *
>> + * This file implements early detection/parsing of I/O mapping
>> + * reported to OS through firmware via I/O Remapping Table (IORT)
>> + * IORT document number: ARM DEN 0049A
>> + */
>> +
>> +#define pr_fmt(fmt)	"ACPI: IORT: " fmt
>> +
>> +#include <linux/export.h>
>> +#include <linux/iort.h>
>> +#include <linux/irqdomain.h>
>> +#include <linux/kernel.h>
>> +#include <linux/pci.h>
>> +
>> +struct iort_its_msi_chip {
>> +	struct list_head	list;
>> +	struct fwnode_handle	*fw_node;
>> +	u32			translation_id;
>> +};
>> +
>> +typedef acpi_status (*iort_find_node_callback)
>> +	(struct acpi_iort_node *node, void *context);
>> +
>> +/* Root pointer to the mapped IORT table */
>> +static struct acpi_table_header *iort_table;
>
> A question to be sorted out:
>
> We assume we can rely on the iort_table pointer, obtained through
> acpi_get_table(), since we assume acpi_glb_permanent_mmap is set (?),
> correct ?
>
> x86 DMAR code seems to rely on that (without even checking
> acpi_gbl_permanent_mmap) and this has consequences on when
> we can really start parsing IORT entries through this patch
> (because if acpi_gbl_permanent_mmap is not set while using
> IORT nodes we would dereference unmapped pointers).
>
> @Rafael: can you confirm that's the right approach ?
>
>> +static LIST_HEAD(iort_msi_chip_list);
>> +static DEFINE_SPINLOCK(iort_msi_chip_lock);
>> +
>> +/**
>> + * iort_register_domain_token() - register domain token and related ITS ID
>> + * to the list from where we can get it back later on.
>> + * @translation_id: ITS ID.
>> + * @token: Domain token.
>> + *
>> + * Returns: 0 on success, -ENOMEM if no memory when allocating list element
>> + */
>> +int iort_register_domain_token(int trans_id, struct fwnode_handle *fw_node)
>> +{
>> +	struct iort_its_msi_chip *its_msi_chip;
>> +
>> +	its_msi_chip = kzalloc(sizeof(*its_msi_chip), GFP_KERNEL);
>> +	if (!its_msi_chip)
>> +		return -ENOMEM;
>> +
>> +	its_msi_chip->fw_node = fw_node;
>> +	its_msi_chip->translation_id = trans_id;
>> +
>> +	spin_lock(&iort_msi_chip_lock);
>> +	list_add(&its_msi_chip->list, &iort_msi_chip_list);
>> +	spin_unlock(&iort_msi_chip_lock);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * iort_deregister_domain_token() - Deregister domain token based on ITS ID
>> + * @translation_id: ITS ID.
>> + *
>> + * Returns: none.
>> + */
>> +void iort_deregister_domain_token(int trans_id)
>> +{
>> +	struct iort_its_msi_chip *its_msi_chip, *t;
>> +
>> +	spin_lock(&iort_msi_chip_lock);
>> +	list_for_each_entry_safe(its_msi_chip, t, &iort_msi_chip_list, list) {
>> +		if (its_msi_chip->translation_id == trans_id) {
>> +			list_del(&its_msi_chip->list);
>> +			kfree(its_msi_chip);
>> +			break;
>> +		}
>> +	}
>> +	spin_unlock(&iort_msi_chip_lock);
>> +}
>> +
>> +/**
>> + * iort_find_domain_token() - Find domain token based on given ITS ID
>> + * @translation_id: ITS ID.
>> + *
>> + * Returns: domain token when find on the list, NULL otherwise
>> + */
>> +struct fwnode_handle *iort_find_domain_token(int trans_id)
>> +{
>> +	struct fwnode_handle *fw_node = NULL;
>> +	struct iort_its_msi_chip *its_msi_chip;
>> +
>> +	spin_lock(&iort_msi_chip_lock);
>> +	list_for_each_entry(its_msi_chip, &iort_msi_chip_list, list) {
>> +		if (its_msi_chip->translation_id == trans_id) {
>> +			fw_node = its_msi_chip->fw_node;
>> +			break;
>> +		}
>> +	}
>> +	spin_unlock(&iort_msi_chip_lock);
>> +
>> +	return fw_node;
>> +}
>
> You are lumping irq_domain/MSI/ITS code and basic IORT (core) support
> in one patch, I would split them in two.

OK

>
>> +static struct acpi_iort_node *
>> +iort_scan_node(enum acpi_iort_node_type type,
>> +	       iort_find_node_callback callback, void *context)
>> +{
>> +	struct acpi_iort_node *iort_node, *iort_end;
>> +	struct acpi_table_iort *iort;
>> +	int i;
>> +
>> +	/* Get the first IORT node */
>> +	iort = (struct acpi_table_iort *)iort_table;
>> +	iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort,
>> +				 iort->node_offset);
>> +	iort_end = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
>> +				iort_table->length);
>> +
>> +	for (i = 0; i < iort->node_count; i++) {
>> +		if (WARN_TAINT(iort_node >= iort_end, TAINT_FIRMWARE_WORKAROUND,
>> +			       "IORT node pointer overflows, bad table!\n"))
>> +			return NULL;
>> +
>> +		if (iort_node->type == type) {
>> +			if (ACPI_SUCCESS(callback(iort_node, context)))
>> +				return iort_node;
>> +		}
>> +
>> +		iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
>> +					 iort_node->length);
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +static acpi_status
>> +iort_match_node_callback(struct acpi_iort_node *node, void *context)
>> +{
>> +	struct device *dev = context;
>> +
>> +	switch (node->type) {
>> +	case ACPI_IORT_NODE_NAMED_COMPONENT: {
>> +		struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
>> +		struct acpi_device *adev = to_acpi_device_node(dev->fwnode);
>> +		struct acpi_iort_named_component *ncomp;
>> +
>> +		if (!adev)
>> +			break;
>> +
>> +		ncomp = (struct acpi_iort_named_component *)node->node_data;
>> +
>> +		if (ACPI_FAILURE(acpi_get_name(adev->handle,
>> +					       ACPI_FULL_PATHNAME, &buffer))) {
>> +			dev_warn(dev, "Can't get device full path name\n");
>> +			break;
>> +		}
>> +
>> +		if (!strcmp(ncomp->device_name, (char *)buffer.pointer))
>> +			return AE_OK;
>> +
>> +		break;
>> +	}
>> +	case ACPI_IORT_NODE_PCI_ROOT_COMPLEX: {
>> +		struct acpi_iort_root_complex *pci_rc;
>> +		struct pci_bus *bus;
>> +
>> +		bus = to_pci_bus(dev);
>> +		pci_rc = (struct acpi_iort_root_complex *)node->node_data;
>> +
>> +		/*
>> +		 * It is assumed that PCI segment numbers maps one-to-one
>> +		 * with root complexes. Each segment number can represent only
>> +		 * one root complex.
>> +		 */
>> +		if (pci_rc->pci_segment_number == pci_domain_nr(bus))
>> +			return AE_OK;
>> +
>> +		break;
>> +	}
>> +	}
>> +
>> +	return AE_NOT_FOUND;
>> +}
>> +
>> +static struct acpi_iort_node *
>> +iort_node_map_rid(struct acpi_iort_node *node, u32 rid_in,
>> +		  u32 *rid_out, u8 type)
>> +{
>> +
>> +	if (!node)
>> +		goto out;
>
> Mmmm..can you explain to me what's the logic here ?

As Marc pointed out, the logic is not consistent now.

iort_node_map_rid IMO should map rid and return parent node which 
provide final translation e.g. IORT or SMMU node. In case of any error 
it should return NULL and provide 1:1 RID mapping (rid_out = rid_in).

>
>> +	/* Go upstream */
>> +	while (node->type != type) {
>> +		struct acpi_iort_id_mapping *id;
>> +		int i, found = 0;
>> +
>> +		/* Exit when no mapping array */
>> +		if (!node->mapping_offset || !node->mapping_count)
>> +			return NULL;
>> +
>> +		id = ACPI_ADD_PTR(struct acpi_iort_id_mapping, node,
>> +				  node->mapping_offset);
>> +
>> +		for (i = 0, found = 0; i < node->mapping_count; i++, id++) {
>> +			/*
>> +			 * Single mapping is not translation rule,
>> +			 * lets move on for this case
>> +			 */
>> +			if (id->flags & ACPI_IORT_ID_SINGLE_MAPPING) {
>> +				if (node->type != ACPI_IORT_NODE_SMMU) {
>
> This is wrong (ie node can be an SMMU v3 and an ITS group).

Right, ITS will never get to this point but SMMU v3 can. I will invert 
condition to:
	if (node->type == ACPI_IORT_NODE_NAMED_COMPONENT ||
	    node->type == ACPI_IORT_NODE_PCI_ROOT_COMPLEX) {
	[...]
	}

>
>> +					rid_in = id->output_base;
>> +					found = 1;
>> +					break;
>> +				}
>> +
>> +				pr_warn(FW_BUG "[node %p type %d] SINGLE MAPPING flag not allowed for SMMU node, skipping ID map\n",
>> +					node, node->type);
>> +				continue;
>> +			}
>> +
>> +			if (rid_in < id->input_base ||
>> +			    (rid_in > id->input_base + id->id_count))
>> +				continue;
>> +
>> +			rid_in = id->output_base + (rid_in - id->input_base);
>> +			found = 1;
>> +			break;
>> +		}
>> +
>
> This inner loop is getting too complicated (and this function with
> it) to my taste. Is it reasonable to factor it out in a separate
> function ?

I will try to put it to another fundtion.

>
>> +		if (!found)
>> +			return NULL;
>> +
>> +		/* Firmware bug! */
>> +		if (!id->output_reference) {
>> +			pr_err(FW_BUG "[node %p type %d] ID map has NULL parent reference\n",
>> +			       node, node->type);
>> +			return NULL;
>> +		}
>> +
>> +		node = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
>> +				    id->output_reference);
>> +	}
>> +
>> +out:
>> +	if (rid_out)
>> +		*rid_out = rid_in;
>> +	return node;
>> +}
>> +
>> +static struct acpi_iort_node *
>> +iort_find_dev_node(struct device *dev)
>> +{
>> +	struct pci_bus *pbus;
>> +
>> +	if (!dev_is_pci(dev))
>> +		return iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
>> +				      iort_match_node_callback, dev);
>> +
>> +	/* Find a PCI root bus */
>> +	pbus = to_pci_dev(dev)->bus;
>> +	while (!pci_is_root_bus(pbus))
>> +		pbus = pbus->parent;
>> +
>> +	return iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
>> +			      iort_match_node_callback, &pbus->dev);
>> +}
>> +
>> +/**
>> + * iort_msi_map_rid() - Map a MSI requester ID for a device
>> + * @dev: The device for which the mapping is to be done.
>> + * @req_id: The device requester ID.
>> + *
>> + * Returns: mapped MSI RID on success, input requester ID otherwise
>> + */
>> +u32 iort_msi_map_rid(struct device *dev, u32 req_id)
>> +{
>> +	struct acpi_iort_node *node;
>> +	u32 dev_id;
>> +
>> +	if (!iort_table)
>> +		return req_id;
>> +
>> +	node = iort_find_dev_node(dev);
>> +	if (!node) {
>> +		dev_err(dev, "can't find related IORT node\n");
>> +		return req_id;
>> +	}
>> +
>> +	if (!iort_node_map_rid(node, req_id, &dev_id,
>> +			       ACPI_IORT_NODE_ITS_GROUP))
>> +		return req_id;
>> +
>> +	return dev_id;
>> +}
>> +
>> +/**
>> + * iort_dev_find_its_id() - Find the ITS identifier for a device
>> + * @dev: The device.
>> + * @idx: Index of the ITS identifier list.
>> + * @its_id: ITS identifier.
>> + *
>> + * Returns: 0 on success, appropriate error value otherwise
>> + */
>> +static int
>> +iort_dev_find_its_id(struct device *dev, u32 req_id, unsigned int idx,
>> +		     int *its_id)
>> +{
>> +	struct acpi_iort_its_group *its;
>> +	struct acpi_iort_node *node;
>> +
>> +	node = iort_find_dev_node(dev);
>> +	if (!node) {
>> +		dev_err(dev, "can't find related IORT node\n");
>> +		return -ENXIO;
>> +	}
>> +
>> +	node = iort_node_map_rid(node, req_id, NULL, ACPI_IORT_NODE_ITS_GROUP);
>> +	if (!node) {
>> +		dev_err(dev, "can't find related ITS node\n");
>> +		return -ENXIO;
>> +	}
>> +
>> +	/* Move to ITS specific data */
>> +	its = (struct acpi_iort_its_group *)node->node_data;
>> +	if (idx > its->its_count) {
>> +		dev_err(dev, "requested ITS ID index [%d] is greater than available [%d]\n",
>> +			idx, its->its_count);
>> +		return -ENXIO;
>> +	}
>> +
>> +	*its_id = its->identifiers[idx];
>> +	return 0;
>> +}
>> +
>> +/**
>> + * iort_get_device_domain() - Find MSI domain related to a device
>> + * @dev: The device.
>> + * @req_id: Requester ID for the device.
>> + *
>> + * Returns: the MSI domain for this device, NULL otherwise
>> + */
>> +struct irq_domain *
>> +iort_get_device_domain(struct device *dev, u32 req_id)
>> +{
>> +	static struct fwnode_handle *handle;
>> +	int its_id;
>> +
>> +	if (!iort_table)
>> +		return NULL;
>> +
>> +	if (iort_dev_find_its_id(dev, req_id, 0, &its_id))
>                                                ^
> This is supposed to be an index in the ITS identifiers list and it is
> always 0 (I *guess* that's because _any_ identifier in that group
> would do but I want to undestand why), please explain :)

Well, we do not have infrastructure to decide which index would be 
better and since any index is fine from the iort_get_device_domain() 
perspecitive, I just used 0 here.

>
> One reason more why I think you should split this patch in two
> so that it becomes easier for Marc to review the ITS specific
> bits:
>
> - IORT core
> - ITS/MSI IORT handling
>
>> +		return NULL;
>> +
>> +	handle = iort_find_domain_token(its_id);
>> +	if (!handle)
>> +		return NULL;
>> +
>> +	return irq_find_matching_fwnode(handle, DOMAIN_BUS_PCI_MSI);
>> +}
>> +
>> +static int __init iort_table_detect(void)
>> +{
>> +	acpi_status status;
>> +
>> +	if (acpi_disabled)
>> +		return -ENODEV;
>> +
>> +	status = acpi_get_table(ACPI_SIG_IORT, 0, &iort_table);
>> +	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
>> +		const char *msg = acpi_format_exception(status);
>> +		pr_err("Failed to get table, %s\n", msg);
>> +		return -EINVAL;
>> +	}
>> +
>> +	return 0;
>> +}
>> +arch_initcall(iort_table_detect);
>
> To prevent calling it from an initcall we can call it from arch
> code (but careful about the iort_table pointer validity, see above).
>
> We should settle the iort_table pointer validity first, everything
> else depends on it.

Yes.

Thanks,
Tomasz

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