From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" 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> 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-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <5473CADA.6040307-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Li, Aubrey" Cc: Lan Tianyu , lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org, robert.moore-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, lv.zheng-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, shigorin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, adamw-cfjF3rc+CpsYNetmKr+vY16hYfS7NtTn@public.gmane.org, jan.brummer-sgYkR6nYkOfYtjvyW6yDsg@public.gmane.org, mika.westerberg-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-E0kO6a4B6psdnm+yROfE0A@public.gmane.org List-Id: linux-i2c@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.