linux-kernel - Re: [PATCH] Input: synaptics-rmi4 - Do not set reduced reporting mode thresholds are not set by the driver

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Date:   Thu, 12 Mar 2020 11:11:36 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Peter Hutterer <peter.hutterer@...-t.net>,
        Andrew Duggan <aduggan@...aptics.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Paul Hollinsky <phollinsky@...technik.com>,
        Christopher Heiny <Cheiny@...aptics.com>,
        kernel@...gutronix.de, patchwork-lst@...gutronix.de
Subject: Re: [PATCH] Input: synaptics-rmi4 - Do not set reduced reporting
 mode thresholds are not set by the driver

Hi Peter,

On Do, 2020-03-12 at 13:14 +1000, Peter Hutterer wrote:
> Hi Andrew,
> 
> On Wed, Mar 11, 2020 at 05:55:49PM -0700, Andrew Duggan wrote:
> > The previous patch "c5ccf2ad3d33 (Input: synaptics-rmi4 - switch to
> > reduced reporting mode)" enabled reduced reporting mode
> > unintentionally
> > on some devices, if the firmware was configured with default Delta
> > X/Y
> > threshold values. The result unintentionally degrade the
> > performance of
> > some touchpads.
> 
> could this be the cause of a stuttering cursor on a P50 as well?
> A recording in the issue below shows the cursor moving by ~25 units per
> event, regardless of the time between those events.
> https://gitlab.freedesktop.org/libinput/libinput/issues/448

Yes, that's very much possible, as reduced reporting mode is about only
reporting events once they cross a predefined movement threshold.

Regards,
Lucas

> thanks!
> 
> Cheers,
>    Peter
> 
> > This patch checks to see that the driver is modifying the delta X/Y
> > thresholds before modifying the reporting mode.
> > 
> > Signed-off-by: Andrew Duggan <aduggan@...aptics.com>
> > ---
> >  drivers/input/rmi4/rmi_f11.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/input/rmi4/rmi_f11.c
> > b/drivers/input/rmi4/rmi_f11.c
> > index 6adea8a3e8fb..ffa39ab153f2 100644
> > --- a/drivers/input/rmi4/rmi_f11.c
> > +++ b/drivers/input/rmi4/rmi_f11.c
> > @@ -1203,8 +1203,8 @@ static int rmi_f11_initialize(struct
> > rmi_function *fn)
> >  	 * If distance threshold values are set, switch to reduced
> > reporting
> >  	 * mode so they actually get used by the controller.
> >  	 */
> > -	if (ctrl->ctrl0_11[RMI_F11_DELTA_X_THRESHOLD] ||
> > -	    ctrl->ctrl0_11[RMI_F11_DELTA_Y_THRESHOLD]) {
> > +	if (sensor->axis_align.delta_x_threshold ||
> > +	    sensor->axis_align.delta_y_threshold) {
> >  		ctrl->ctrl0_11[0] &= ~RMI_F11_REPORT_MODE_MASK;
> >  		ctrl->ctrl0_11[0] |= RMI_F11_REPORT_MODE_REDUCED;
> >  	}
> > -- 
> > 2.20.1
> >