Re: [REGRESSION] hwmon: (applesmc) avoid overlong udelay()

Guenter Roeck
2020-09-30T16:44:52Z

On Wed, Sep 30, 2020 at 10:54:42AM +0200, Andreas Kemnade wrote:
> Hi,
>
> after the $subject patch I get lots of errors like this:

For reference, this refers to commit fff2d0f701e6 ("hwmon: (applesmc)
avoid overlong udelay()").

> [ 120.378614] applesmc: send_byte(0x00, 0x0300) fail: 0x40
> [ 120.378621] applesmc: LKSB: write data fail
> [ 120.512782] applesmc: send_byte(0x00, 0x0300) fail: 0x40
> [ 120.512787] applesmc: LKSB: write data fail
>
> CPU sticks at low speed and no fan is turning on.
> Reverting this patch on top of 5.9-rc6 solves this problem.
>
> Some information from dmidecode:
>
> Base Board Information
> Manufacturer: Apple Inc.
> Product Name: Mac-7DF21CB3ED6977E5
> Version: MacBookAir6,2
>
> Handle 0x0020, DMI type 11, 5 bytes OEM Strings String 1: Apple ROM Version. Model: …,
> Handle 0x0020, DMI type 11, 5 bytes
> OEM Strings
> String 1: Apple ROM Version. Model: MBA61. EFI Version: 122.0.0
> String 2: .0.0. Built by: root@saumon. Date: Wed Jun 10 18:
> String 3: 10:36 PDT 2020. Revision: 122 (B&I). ROM Version: F000_B
> String 4: 00. Build Type: Official Build, Release. Compiler: Appl
> String 5: e clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM
> String 6: 3.0svn).
>
> Writing to things in /sys/devices/platform/applesmc.768 gives also the
> said errors.
> But writing 1 to fan1_maunal and 5000 to fan1_output turns the fan on
> despite error messages.
>
Not really sure what to do here. I could revert the patch, but then we'd gain
clang compile failures. Arnd, any idea ?

Guenter