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RE: [PATCH] ACPICA: Export mutex functions

From "Moore, Robert" <robert.moore@intel.com>
Newsgroups linux.kernel
Subject RE: [PATCH] ACPICA: Export mutex functions
Date 2017-04-17 19:20 +0200
Message-ID <txitH-3pf-5@gated-at.bofh.it> (permalink)
References <tvsdQ-64C-27@gated-at.bofh.it> <tvsxb-6br-3@gated-at.bofh.it> <tvxZT-1zC-7@gated-at.bofh.it> <txbix-7rC-1@gated-at.bofh.it> <txheh-2tc-9@gated-at.bofh.it>
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There is a model for the drivers to directly acquire an AML mutex object. That is why the acquire/release public interfaces were added to ACPICA.

I forget all of the details, but the model was developed with MS and others during the ACPI 6.0 timeframe.


> -----Original Message-----
> From: Guenter Roeck [mailto:linux@roeck-us.net]
> Sent: Monday, April 17, 2017 8:57 AM
> To: Zheng, Lv
> Cc: Moore, Robert; Wysocki, Rafael J; Len Brown; linux-
> acpi@vger.kernel.org; devel@acpica.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] ACPICA: Export mutex functions
> 
> Hi,
> 
> On Mon, Apr 17, 2017 at 09:39:35AM +0000, Zheng, Lv wrote:
> > Hi,
> >
> > > From: Guenter Roeck [mailto:linux@roeck-us.net]
> > > Subject: Re: [PATCH] ACPICA: Export mutex functions
> > >
> > > On Wed, Apr 12, 2017 at 03:29:55PM +0000, Moore, Robert wrote:
> > > > The ACPICA mutex functions are based on the host OS functions, so
> they don't really buy you anything.
> > > You should just use the native Linux functions.
> > > >
> > >
> > > You mean they don't really acquire the requested ACPI mutex, and the
> > > underlying DSDT which declares and uses the mutex just ignores if
> > > the mutex was acquired by acpi_acquire_mutex() ?
> > >
> > > To clarify: You are saying that code such as
> > >
> > > 	acpi_status status;
> > >
> > > 	status = acpi_acquire_mutex(NULL, "\\_SB.PCI0.SBRG.SIO1.MUT0",
> 0x10);
> > > 	if (ACPI_FAILURE(status)) {
> > > 		pr_err("Failed to acquire ACPI mutex\n");
> > > 		return -EBUSY;
> > > 	}
> >
> > Why do you need to access \_SB.PCI0.SBRG.SIO1.MUT0?
> > OSPM should only invoke entry methods predefined by ACPI spec or
> whatever specs.
> > There shouldn't be any needs that a driver acquires an arbitrary AML
> mutex.
> > You do not seem to have justified the usage model, IMO.
> >
> 
> I am sorry, I have no idea how to do that. I can see that the resource in
> question (IO address 0x2e/0x2f) is accessed from the DSDT, that the
> resource is mutex protected, and that accesses to the same IO address from
> the Linux kernel are unreliable unless I acquire the mutex in question. At
> the same time, I can see that request_muxed_region() succeeds, so
> presumably ACPI does not reserve the region for its exclusive use.
> 
> It may well be that the "official" response to this problem is "you must
> not instantiate a watchdog, environmental monitor, or gpio driver (or
> anything else provided by the Super-IO chip that requires access to those
> ports) on this platform in Linux". Is that what you are suggesting ?
> 
> Thanks,
> Guenter

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Thread

[PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-12 17:20 +0200
  RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-12 17:40 +0200
    Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-12 23:30 +0200
      RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-13 00:00 +0200
        Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-13 03:00 +0200
        Re: [PATCH] ACPICA: Export mutex functions "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-04-15 00:40 +0200
          RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-15 01:40 +0200
      RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-17 11:40 +0200
        RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-17 11:50 +0200
          Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-17 16:10 +0200
            RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 01:40 +0200
        Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-17 18:00 +0200
          RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-17 19:20 +0200
            RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-17 21:30 +0200
              Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-17 21:50 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-17 22:50 +0200
                Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-17 23:10 +0200
                Re: [PATCH] ACPICA: Export mutex functions "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-17 23:30 +0200
                Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-18 00:40 +0200
                Re: [PATCH] ACPICA: Export mutex functions "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-18 01:00 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 02:00 +0200
                Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-18 06:40 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 09:10 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 09:20 +0200
                Re: [PATCH] ACPICA: Export mutex functions Guenter Roeck <linux@roeck-us.net> - 2017-04-18 16:00 +0200
                Re: [PATCH] ACPICA: Export mutex functions "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-04-18 16:30 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-18 18:10 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-19 03:30 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-19 03:40 +0200
                RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 02:00 +0200
              RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 01:50 +0200
            RE: [PATCH] ACPICA: Export mutex functions "Moore, Robert" <robert.moore@intel.com> - 2017-04-17 21:40 +0200
          RE: [PATCH] ACPICA: Export mutex functions "Zheng, Lv" <lv.zheng@intel.com> - 2017-04-18 01:40 +0200

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