linux-kernel - [REGRESSION] hwmon: (applesmc) avoid overlong udelay()

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Date:   Wed, 30 Sep 2020 10:54:42 +0200
From:   Andreas Kemnade <andreas@...nade.info>
To:     rydberg@...math.org, jdelvare@...e.com, linux@...ck-us.net,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [REGRESSION] hwmon: (applesmc) avoid overlong udelay()

Hi,

after the $subject patch I get lots of errors like this:
[  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@...mon.  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.

Config used is: https://misc.andi.de1.cc/mac-config.gz

Regards,
Andreas