linux-kernel - Re: [RFC PATCH 04/14] ACPI: Add ACPI 5.0 Time and Alarm Device driver

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Date:	Wed, 08 Jan 2014 22:59:02 +0800
From:	joeyli <jlee@...e.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <matthew.garrett@...ula.com>, Elliott@...com,
	samer.el-haj-mahmoud@...com, Oliver Neukum <oneukum@...e.de>,
	werner@...e.com, trenn@...e.de, JBeulich@...e.com,
	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	x86@...nel.org,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	linux-acpi@...r.kernel.org
Subject: Re: [RFC PATCH 04/14] ACPI: Add ACPI 5.0 Time and Alarm Device
 driver

於 二，2014-01-07 於 08:35 -0800，H. Peter Anvin 提到：
> On 01/07/2014 02:40 AM, joeyli wrote:
> > 
> > Due to accessing CMOS through ASL need enable SMM support in OVMF,
> 
> Why?  The CMOS is its own ASL address space, and you need that anyway to
> be able to access the RTC proper.  If you don't want to use it because
> you don't want to export any indication of a legacy RTC you should be
> able to just do I/O port references directly in your ASL.
> 
> 	-hpa
> 
> 

ACPICA denied AML access RTC ports.

I tried to access 0x70, 0x71 ports in ASL on a real machine, ACPICA
denied AML access to those ports. I got the following dmesg:

hwvalid-0188 hw_validate_io_request: Denied AML access to port
0x0000000000000071/1


The code in acpica denied it:

linux/drivers/acpi/acpica/hwvalid.c

 * This provides ACPICA with the desired port protections and
 * Microsoft compatibility.
 *
 * Description of port entries:
[...]
 *  RTC:   Real-time clock
 *  CMOS:  Extended CMOS
[...]
 */
static const struct acpi_port_info acpi_protected_ports[] = {
[...]
        {"RTC", 0x0070, 0x0071, ACPI_OSI_WIN_XP},
        {"CMOS", 0x0074, 0x0076, ACPI_OSI_WIN_XP},


Document of Windows XP:
http://www.freelists.org/post/windows_errors/what-error-messages-really-mean-WinXP-IO-Ports-Blocked-from-Bios-AML-on-Windows-XP


If just for ACPI TAD testing, we can remove the port protection check of
RTC ports in hwvalid.c. I have read 0x70/0x71 port success after removed
the checking in acpica/hwvalid.c.

I will try to write RTC port in AML after remove acpica check, maybe
have other unpredictable situation.


Thanks a lot!
Joey Lee

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