linux-kernel - Re: [PATCH] applesmc: Re-work SMC comms v2

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Message-ID: <20201105091228.128624ba@aktux>
Date:   Thu, 5 Nov 2020 09:12:28 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Brad Campbell <brad@...rfbargle.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Arnd Bergmann <arnd@...db.de>, rydberg@...math.org,
        linux-hwmon@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        hns@...delico.com
Subject: Re: [PATCH] applesmc: Re-work SMC comms v2

On Thu, 5 Nov 2020 18:26:24 +1100
Brad Campbell <brad@...rfbargle.com> wrote:

> Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") introduced
> an issue whereby communication with the SMC became unreliable with write
> errors like :
> 
> [  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
> 
> The original code appeared to be timing sensitive and was not reliable with
> the timing changes in the aforementioned commit.
> 
> This patch re-factors the SMC communication to remove the timing 
> dependencies and restore function with the changes previously committed.
> 
> v2 : Address logic and coding style
> 
> Reported-by: Andreas Kemnade <andreas@...nade.info>
> Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()")
> Signed-off-by: Brad Campbell <brad@...rfbargle.com>
> 
Still works here:
Tested-by: Andreas Kemnade <andreas@...nade.info> # MacBookAir6,2