From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: "Li, Aubrey" <aubrey.li@linux.intel.com>
Cc: Lan Tianyu <tianyu.lan@intel.com>, lenb@kernel.org, wsa@the-dreams.de,
        robert.moore@intel.com, lv.zheng@intel.com, shigorin@gmail.com,
        adamw@happyassassin.net, jan.brummer@tabos.org,
        mika.westerberg@linux.intel.com, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
        devel@acpica.org
Subject: Re: [PATCH V3] ACPI: Add _DEP(Operation Region Dependencies) support to fix battery issue on the Asus T100TA
Date: Tue, 25 Nov 2014 02:16:32 +0100
Message-ID: <2504006.9dfaR2IgVp@vostro.rjw.lan>
User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; )
In-Reply-To: <5473CADA.6040307@linux.intel.com>
References: <1416748974-24124-1-git-send-email-tianyu.lan@intel.com> <1720074.U59stZW2tQ@vostro.rjw.lan> <5473CADA.6040307@linux.intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="utf-8"
Sender: linux-kernel-owner@vger.kernel.org

On Tuesday, November 25, 2014 08:18:34 AM Li, Aubrey wrote:
> On 2014/11/24 23:27, Rafael J. Wysocki wrote:
> > On Monday, November 24, 2014 10:39:55 AM Li, Aubrey wrote:
> >> On 2014/11/23 21:22, Lan Tianyu wrote:
> >>> ACPI 5.0 introduces _DEP to designate device objects that OSPM should
> >>> assign a higher priority in start ordering due to future operation region
> >>> accesses.
> >>>
> >>> On Asus T100TA, ACPI battery info are read from a I2C slave device via
> >>> I2C operation region. Before I2C operation region handler is installed,
> >>> battery _STA always returns 0. There is a _DEP method of designating
> >>> start order under battery device node.
> >>>
> >>> This patch is to implement _DEP feature to fix battery issue on the Asus T100TA.
> >>> Introducing acpi_dep_list and adding dep_unmet count in the struct
> >>> acpi_device. During ACPI namespace scan, create struct acpi_dep_data for a
> >>> valid pair of master (device pointed to by _DEP)/slave(device with _DEP), record
> >>> master's and slave's ACPI handle in it and put it into acpi_dep_list. The dep_unmet
> >>> count will increase by one if there is a device under its _DEP. Driver's probe() should
> >>> return EPROBE_DEFER when find dep_unmet is larger than 0. When I2C operation
> >>> region handler is installed, remove all struct acpi_dep_data on the acpi_dep_list
> >>> whose master is pointed to I2C host controller and decrease slave's dep_unmet.
> >>> When dep_unmet decreases to 0, all _DEP conditions are met and then do acpi_bus_attach()
> >>> for the device in order to resolve battery _STA issue on the Asus T100TA.
> >>
> >> Well, Can we explicitly tied this up with ASUS T100TA in the code?
> >> If I understand correctly, the assumption in the patch is that the
> >> battery device only depends on I2C device, which is true on ASUS T100TA,
> >> but may not on the other platforms.
> >>
> >> This patch does not work on a box I have, on it _DEP contains I2C and GPIO.
> > 
> > Does the patch break anything for you?
> 
> Not I'm aware so far.

OK

It is not a complete solution, but it is an improvement.  It evidently helps
people.

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/