linux-kernel - Re: [PATCH v3 10/12] HID: ft260: wake up device from power saving mode

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Date:   Mon, 31 Oct 2022 18:12:51 +0100
From:   Enrik Berkhan <Enrik.Berkhan@...a.de>
To:     Michael Zaidman <michael.zaidman@...il.com>, jikos@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org, germain.hebert@...abb.com
Subject: Re: [PATCH v3 10/12] HID: ft260: wake up device from power saving
 mode

Hi Michael,

On Sun, 2022-10-30 at 22:34 +0200, Michael Zaidman wrote:
> The FT260 can enter a power saving mode after being idle for longer than
> 5 seconds.
> 
> When being woken up from power saving mode by an I2C write request, it
> looks like a possible NACK will not be correctly reported back. As a
> workaround, the driver will request an I2C status report before starting
> the next I2C transfer if the FT260 has been idle for longer than 4800ms.

Unfortunately, I have found issues with this patch as it is. When I
tested from an installation running in KVM, I saw missed NACKs again.

A possible fix seems to be to send the extra status request after the
output report triggering the write. See
https://github.com/MichaelZaidman/hid-ft260/pull/7.

Cheers,
Enrik