Re: [PATCH V10 1/8] ACPI: I/O Remapping Table (IORT) initial support

[Dennis Chen <dennis.chen@arm.com>]

Hi Tomasz,

On Tue, Sep 06, 2016 at 11:08:51AM +0200, Tomasz Nowicki wrote:
[...]
> +static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
> +		       u32 *rid_out)
> +{
> +	/* Single mapping does not care for input id */
> +	if (map->flags & ACPI_IORT_ID_SINGLE_MAPPING) {
> +		if (type == ACPI_IORT_NODE_NAMED_COMPONENT ||
> +		    type == ACPI_IORT_NODE_PCI_ROOT_COMPLEX) {
> +			*rid_out = map->output_base;
> +			return 0;
> +		}
> +
> +		pr_warn(FW_BUG "[map %p] SINGLE MAPPING flag not allowed for node type %d, skipping ID map\n",
> +			map, type);
> +		return -ENXIO;
> +	}
> +
> +	if (rid_in < map->input_base ||
> +	    (rid_in >= map->input_base + map->id_count))
> +		return -ENXIO;
> +
> +	*rid_out = map->output_base + (rid_in - map->input_base);
> +	return 0;
> +}
> +
> +static struct acpi_iort_node *iort_node_map_rid(struct acpi_iort_node *node,
> +						u32 rid_in, u32 *rid_out,
> +						u8 type)
> +{
> +	u32 rid = rid_in;
> +
> +	/* Parse the ID mapping tree to find specified node type */
> +	while (node) {
> +		struct acpi_iort_id_mapping *map;
> +		int i;
> +
> +		if (node->type == type) {
> +			if (rid_out)
> +				*rid_out = rid;
> +			return node;
> +		}
> +
> +		if (!node->mapping_offset || !node->mapping_count)
> +			goto fail_map;
If node->mapping_count is zero, then node->mapping_offset must be zero. A firmware bug
otherwise?
> +
> +		map = ACPI_ADD_PTR(struct acpi_iort_id_mapping, node,
> +				   node->mapping_offset);
> +
> +		/* Firmware bug! */
> +		if (!map->output_reference) {
> +			pr_err(FW_BUG "[node %p type %d] ID map has NULL parent reference\n",
> +			       node, node->type);
> +			goto fail_map;
> +		}
> +
> +		/* Do the RID translation */
> +		for (i = 0; i < node->mapping_count; i++, map++) {
> +			if (!iort_id_map(map, node->type, rid, &rid))
> +				break;
> +		}
>
Just curious about if there is kind of possibility that we can get some reduplicated DeviceIDs
with a deliberate ID mapping design in FW for the SMMU/RC node. For instance, for a system with 2
PCIe RCs both behind an individual SMMU device, how to make sure the StreamID mapped is unique 
across the entire system, the same for DeviceID mapped. 
Anyway, this is my personal confusion, maybe it's not a problem at all for current design ;-)

Thanks,
Dennis
> +
> +		if (i == node->mapping_count)
> +			goto fail_map;
> +
> +		node = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
> +				    map->output_reference);
> +	}
> +
> +fail_map:
> +	/* Map input RID to output RID unchanged on mapping failure*/
> +	if (rid_out)
> +		*rid_out = rid_in;
> +
> +	return NULL;
> +}
> +
> +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);
> +}
> +
> +void __init acpi_iort_init(void)
> +{
> +	acpi_status status;
> +
> +	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);
> +	}
> +}
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index 85b7d07..e56e643 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -36,6 +36,7 @@
>  #ifdef CONFIG_X86
>  #include <asm/mpspec.h>
>  #endif
> +#include <linux/acpi_iort.h>
>  #include <linux/pci.h>
>  #include <acpi/apei.h>
>  #include <linux/dmi.h>
> @@ -1186,6 +1187,7 @@ static int __init acpi_init(void)
>  	}
>  
>  	pci_mmcfg_late_init();
> +	acpi_iort_init();
>  	acpi_scan_init();
>  	acpi_ec_init();
>  	acpi_debugfs_init();
> diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> new file mode 100644
> index 0000000..fcacaf7
> --- /dev/null
> +++ b/include/linux/acpi_iort.h
> @@ -0,0 +1,30 @@
> +/*
> + * 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 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.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
> + * Place - Suite 330, Boston, MA 02111-1307 USA.
> + */
> +
> +#ifndef __ACPI_IORT_H__
> +#define __ACPI_IORT_H__
> +
> +#include <linux/acpi.h>
> +
> +#ifdef CONFIG_ACPI_IORT
> +void acpi_iort_init(void);
> +#else
> +static inline void acpi_iort_init(void) { }
> +#endif
> +
> +#endif /* __ACPI_IORT_H__ */
> -- 
> 1.9.1
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>