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Date:   Fri, 21 Jul 2023 16:53:48 -0700
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Jeffery Miller <jefferymiller@google.com>
Cc:     Jonathan Denose <jdenose@chromium.org>, jdenose@google.com,
        Lyude Paul <lyude@redhat.com>, benjamin.tissoires@redhat.com,
        Andrew Duggan <andrew@duggan.us>, loic.poulain@linaro.org,
        Andrew Duggan <aduggan@synaptics.com>,
        Javier Martinez Canillas <javierm@redhat.com>,
        Jeremy Kerr <jk@codeconstruct.com.au>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
        <u.kleine-koenig@pengutronix.de>, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] Input: synaptics-rmi4 - retry reading SMBus version
 on resume
Message-ID: <ZLsajIm2qTcLE+O7@google.com>
References: <20230608210404.722123-1-jefferymiller@google.com>
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In-Reply-To: <20230608210404.722123-1-jefferymiller@google.com>
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Hi Jeffery,

On Thu, Jun 08, 2023 at 09:04:00PM +0000, Jeffery Miller wrote:
> On resume there can be a period of time after the
> preceding serio_resume -> psmouse_deactivate call
> where calls to rmi_smb_get_version fail with
> -ENXIO.
> 
> The call path in rmi_smb_resume is rmi_smb_resume -> rmi_smb_reset ->
> rmi_smb_enable_smbus_mode -> rmi_smb_get_version where
> this failure would occur.
> 
> Add a 30ms delay and retry in the ENXIO case to ensure the following
> rmi_driver_resume calls in rmi_smbus_resume can succeed.
> 
> This behavior was seen on a Lenovo T440p machine that required
> a delay of approximately 7-12ms.
> 
> The 30ms delay was chosen based on the linux-input message:
> Link: https://lore.kernel.org/all/BYAPR03MB47572F2C65E52ED673238D41B2439@BYAPR03MB4757.namprd03.prod.outlook.com/

I do not quite like putting these retries in RMI code. I wonder if we
should not move the delay into psmouse_smbus_reconnect():

	if (smbdev->need_deactivate) {
		psmouse_deactivate(psmouse);
		/* Give the device time to switch to SMBus mode */
		msleep(30);
	}

or even factor it out into psmouse_activate_smbus_mode() and call it
from psmouse_smbus_reconnect() as well as psmouse_smbus_init().

Thanks.

or even factor it out into psmouse_activate_smbus_mode() and call it
from psmouse_smbus_reconnect() as well as psmouse_smbus_init().

Thanks.

-- 
Dmitry