linux-kernel - Re: [PATCH V8 1/8] ACPI: I/O Remapping Table (IORT) initial support

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Date:	Thu, 18 Aug 2016 08:25:20 +0200
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>, rafael@...nel.org
Cc:	marc.zyngier@....com, tglx@...utronix.de, jason@...edaemon.net,
	rjw@...ysocki.net, helgaas@...nel.org, will.deacon@....com,
	catalin.marinas@....com, hanjun.guo@...aro.org,
	shijie.huang@....com, robert.richter@...iumnetworks.com,
	mw@...ihalf.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org,
	andrea.gallo@...aro.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, al.stone@...aro.org,
	graeme.gregory@...aro.org, ddaney.cavm@...il.com,
	okaya@...eaurora.org
Subject: Re: [PATCH V8 1/8] ACPI: I/O Remapping Table (IORT) initial support

On 12.08.2016 18:33, Lorenzo Pieralisi wrote:
> Hi Tomasz,
>
> On Thu, Aug 11, 2016 at 12:06:31PM +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.
>> http://infocenter.arm.com/help/topic/com.arm.doc.den0049b/DEN0049B_IO_Remapping_Table.pdf
>>
>> Initial support allows to detect IORT table presence and save its
>> root pointer obtained through acpi_get_table(). The pointer validity
>> depends on acpi_gbl_permanent_mmap because if acpi_gbl_permanent_mmap
>> is not set while using IORT nodes we would dereference unmapped pointers.
>>
>> For the aforementioned reason call iort_table_detect() from acpi_init()
>> which guarantees acpi_gbl_permanent_mmap to be set at that point.
>
> We still need to get Rafael ACK on this, keeping in mind that the
> eg code parsing DMAR table relies on the same assumption.

Exactly.

Rafael, can you please have a look ?

>
> [...]
>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index 445ce28..6cef2d1 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -521,4 +521,9 @@ config ACPI_CONFIGFS
>>  	  userspace. The configurable ACPI groups will be visible under
>>  	  /config/acpi, assuming configfs is mounted under /config.
>>
>> +if ARM64
>> +source "drivers/acpi/arm64/Kconfig"
>> +
>
> Just curious: Why do you need a space ?

No good reason, it will disappear for next version.

>
>> +endif
>> +
>>  endif	# ACPI
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index 5ae9d85..e5ada78 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -105,3 +105,5 @@ obj-$(CONFIG_ACPI_CONFIGFS)	+= acpi_configfs.o
>>
>>  video-objs			+= acpi_video.o video_detect.o
>>  obj-y				+= dptf/
>> +
>> +obj-$(CONFIG_ARM64)		+= arm64/
>> diff --git a/drivers/acpi/arm64/Kconfig b/drivers/acpi/arm64/Kconfig
>> new file mode 100644
>> index 0000000..fc818dc
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/Kconfig
>> @@ -0,0 +1,6 @@
>> +#
>> +# ACPI Configuration for ARM64
>> +#
>> +
>> +config IORT_TABLE
>> +	bool
>> diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
>> new file mode 100644
>> index 0000000..d01be6f
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/Makefile
>> @@ -0,0 +1 @@
>> +obj-$(CONFIG_IORT_TABLE) 	+= iort.o
>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>> new file mode 100644
>> index 0000000..f89056e
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/iort.c
>> @@ -0,0 +1,218 @@
>> +/*
>> + * 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/iort.h>
>> +#include <linux/kernel.h>
>> +#include <linux/pci.h>
>> +
>> +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;
>
> See above.
>
> [...]
>
>> +void __init iort_table_detect(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..55a84da 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/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();
>> +	iort_table_detect();
>
> That's another bit we have to make sure Rafael is ok with, given
> that IORT is ARM64 specific (but we stub it out if it is not
> configured).
>
> Having said that:
>
> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

Thanks for your time.

Tomasz