linux-kernel - Re: Help configuring kernel for Baytrail system

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Message-ID: <CAHp75Vcxp=JHUccy4sU3mYxGS5HK-YkY9=_Vaez+s2hfWXwRow@mail.gmail.com>
Date:	Thu, 25 Jun 2015 20:30:46 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Nicolas George <george@...p.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Box <david.e.box@...ux.intel.com>
Subject: Re: Help configuring kernel for Baytrail system

On Mon, Jun 15, 2015 at 3:41 PM, Nicolas George <george@...p.org> wrote:
> Hi.
>
> I am trying to configure a kernel for a Baytrail SoC-based hybrid laptop (a
> Lenovo Miix 3-1030). Amongst other things, the battery gauge is not
> detected. I suspect it may be related to the following commit:
>
> # commit 894acb2f823b13afacfe40b02efbd9146af58586
> # Author: David Box <david.e.box@...ux.intel.com>
> # Date:   Thu Jan 15 01:12:17 2015 -0800
> #
> #     i2c: designware: Add Intel Baytrail PMIC I2C bus support

Why not to ask David (Cc'ed) directly?


>
> It is very likely that I am missing a simple compile-time or run-time
> option, and in that case, on top of getting the configuration right, I have
> a second question: how could I find the solution by myself?
>
> Here is the problem data:
>
> - The battery gauge works with the kernel from the Ubuntu 15.4 live image.
>   Quite a few other things fail to work with that kernel, so using it is not
>   a solution, but it is proof that it can work.
>
> - I have tried with 3.16 from Debian, 4.0.1 and 4.1-rc* with custom
>   configuration, and the battery is completely invisible. Nothing in dmesg.
>
> - The sysfs entry for the battery is this:
>   /sys/devices/LNXSYSTM:00/LNXSYBUS:00/80860F41:00/PNP0C0A:00
>   It should contain a driver link to bus/acpi/drivers/battery, but it does
>   not.
>
> - Adding custom debug messages, I was able to find that
>   acpi_bus_get_status_handle() evaluates the _STA attribute of the BATC
>   device to 0, meaning the device is not present.
>
> - The corresponding code in the ACPI tables is this:
>
>         Device (BATC)
>         {
>             [...]
>             Method (_STA, 0, NotSerialized)  // _STA: Status
>             {
>                 If ((AVBL == One))
>                 {
>                     BUF7 = CMD7 /* \_SB_.I2C1.CMD7 */
>                     If ((STAT != Zero))
>                     {
>                         Return (Zero)
>                     }
>
>                     Return (0x1F)
>                 }
>
>                 Return (Zero)
>             }
>
>   but I do not know how to debug further. Enabling full ACPI debug messages
>   gives so much output that it is unusable.
>
> - I also suspect that the issue comes from the "dev->pm_runtime_disabled"
>   flag on the corresponding I2C bus entry: it is enabled by
>   i2c_dw_eval_lock_support() with a message "I2C bus managed by PUNIT", and
>   inhibits probing the device. I did not manage to find how to re-enable it.
>
>
> Please let me know if you have any advice on this issue in particular or any
> more general documentation on how to investigate I2C and PLATFORM/ACPI-based
> systems.
>
> In the meantime, I have summarized what I was able to get working on this
> laptop on the following webpage:
> http://nsup.org/~george/comp/linux_lenovo_miix3/
>
> Regards,
>
> --
>   Nicolas George



-- 
With Best Regards,
Andy Shevchenko
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