Re: [PATCH] Input: touchscreen: tsc2007: Reduce I2C transactions for Z2 read

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Sat, May 02, 2026 at 12:53:13PM +0200, Andreas Kemnade wrote:
> Hi,
> 
> On Sun, 19 Apr 2026 17:18:23 -0700
> Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
> 
> > Hi Yuki,
> > 
> > On Fri, Apr 10, 2026 at 04:41:00PM +0900, Yuki Horii wrote:
> > > From: Yuki Horii <yuuki198708@gmail.com>
> > > 
> > > The current implementation sends a separate power-down command
> > > after reading the Z2 value, resulting in an extra I2C
> > > transaction per measurement cycle.
> > > 
> > > The TSC2007 command byte contains a 2-bit power-down mode
> > > selection field. By selecting the power-down state in the Z2
> > > measurement command, the device powers down after the Z2 A/D
> > > conversion completes, eliminating the subsequent power-down
> > > transaction.
> > > 
> > > This reduces the number of I2C transactions by one per touch
> > > measurement cycle, decreasing I2C bus overhead and improving
> > > touch sampling performance.
> > > 
> > > Signed-off-by: Yuki Horii <yuuki198708@gmail.com>
> > > ---
> > >  drivers/input/touchscreen/tsc2007_core.c | 6 ++----
> > >  1 file changed, 2 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/input/touchscreen/tsc2007_core.c b/drivers/input/touchscreen/tsc2007_core.c
> > > index 948935de894b..ff60245baa96 100644
> > > --- a/drivers/input/touchscreen/tsc2007_core.c
> > > +++ b/drivers/input/touchscreen/tsc2007_core.c
> > > @@ -61,10 +61,8 @@ static void tsc2007_read_values(struct tsc2007 *tsc, struct ts_event *tc)
> > >  
> > >  	/* turn y+ off, x- on; we'll use formula #1 */
> > >  	tc->z1 = tsc2007_xfer(tsc, READ_Z1);
> > > -	tc->z2 = tsc2007_xfer(tsc, READ_Z2);
> > > -
> > > -	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
> > > -	tsc2007_xfer(tsc, PWRDOWN);
> > > +	/* Read Z2 and power down ADC after A/D conversion, enable PENIRQ */
> > > +	tc->z2 = tsc2007_xfer(tsc, (TSC2007_POWER_OFF_IRQ_EN | TSC2007_MEASURE_Z2));
> > >  }
> > >  
> > >  u32 tsc2007_calculate_resistance(struct tsc2007 *tsc, struct ts_event *tc)  
> > 
> > Thank you for the patch.
> > 
> > I'd like people using this part to chime in (CCed).
> > 
> This looks like that there might be some reason behind it. But I cannot find any.
> Either by reading the datasheet nor by testing.
> 
> I have checked the interrupt counter. Output seems still be same.
> Interrupts appear when finger is moving.
> 
> So 
> Tested-by: Andreas Kemnade <andreas@kemnade.info> # GTA04

Thank you for giving it a spin Andreas.

Applied, thank you Yuki.

-- 
Dmitry