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Date:   Tue, 25 Jul 2023 22:13:15 -0700
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Jeffery Miller <jefferymiller@google.com>
Cc:     Lyude Paul <lyude@redhat.com>,
        Jonathan Denose <jdenose@chromium.org>, jdenose@google.com,
        Andrew Duggan <aduggan@synaptics.com>,
        Andrew Duggan <andrew@duggan.us>, loic.poulain@linaro.org,
        benjamin.tissoires@redhat.com, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] Input: psmouse - add delay when deactivating for
 SMBus mode
Message-ID: <ZMCra8UjEhJsEc9S@google.com>
References: <20230726025256.81174-1-jefferymiller@google.com>
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On Wed, Jul 26, 2023 at 02:52:48AM +0000, Jeffery Miller wrote:
> There is a period of time between the psmouse deactivate and the
> ability to communicate with the SMBus companion. Insert a
> sleep after the deactivate to account for the delay and ensure
> the SMBus companion is responsive.
> 
> Attempting to read from the SMBus companion too quickly was causing
> the touchpad on machines with an i801_smbus companion to stop working
> after a sleep/resume cycle.
> 
> On resume the rmi4_smbus would fail with errors reading the SMBus version
> number:
> ```
> [5454] i2c_i801:i801_check_post:414: i801_smbus 0000:00:1f.3: No response
> smbus_result: i2c-0 a=02c f=0000 c=fd BYTE_DATA rd res=-6
> rmi4_smbus 0-002c: failed to get SMBus version number!
> ...
> rmi4_f01 rmi4-00.fn01: Failed to restore normal operation: -6.
> rmi4_f01 rmi4-00.fn01: Resume failed with code -6.
> rmi4_physical rmi4-00: Failed to suspend functions: -6
> rmi4_smbus 0-002c: Failed to resume device: -6
> ```
> In this case the rmi_smb_get_version fails with -ENXIO if it happens too
> soon after the preceding serio_resume -> psmouse_deactivate call.
> 
> On boot this issue could cause the touchpad to stay in the limited PS/2
> mode. This only reproduced in 1 in 10 boots on the Lenovo T440p.
> Failures in the log on boot would show up as:
> ```
> psmouse serio1: synaptics: Trying to set up SMBus access
> [122] i2c_i801:i801_check_post:437: i801_smbus 0000:00:1f.3: No response
> psmouse serio1: synaptics: SMbus companion is not ready yet
> ```
> 
> Experimentation on the Lenovo T440p showed that a delay of 7-12ms on
> resume allowed the companion to respond.
> 
> The 30ms delay in this patch was chosen based on the linux-input message:
> Link: https://lore.kernel.org/all/BYAPR03MB47572F2C65E52ED673238D41B2439@BYAPR03MB4757.namprd03.prod.outlook.com/
> 
> Signed-off-by: Jeffery Miller <jefferymiller@google.com>

Applied, thank you.

-- 
Dmitry