linux-kernel - Re: [PATCH v2 2/2] Input: ads7846: convert to one message

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Date:   Wed, 20 Jan 2021 08:40:32 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Mark Brown <broonie@...nel.org>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-spi@...r.kernel.org, David Jander <david@...tonic.nl>
Subject: Re: [PATCH v2 2/2] Input: ads7846: convert to one message


Hi Dmitry,

On Tue, Nov 17, 2020 at 04:31:38PM -0800, Dmitry Torokhov wrote:
> On Tue, Nov 10, 2020 at 09:50:41AM +0100, Oleksij Rempel wrote:
> > Convert multiple full duplex transfers in to a single transfer to reduce
> > CPU load.
> > 
> > Current driver version support following filtering modes:
> > - ads7846_no_filter() - not filtered
> > - ads7846_debounce_filter() - driver specific debounce filter
> > - pdata->filter - platform specific debounce filter (do any platform
> > 	provides such filter?)
> > 
> > Without filter this HW is not really usable, since the physic of
> > resistive touchscreen can provide some bounce effects. With driver internal
> > filter, we have constant amount of retries + debounce retries if some anomaly
> > was detected.
> > 
> > High amount of tiny SPI transfers is the primer reason of high CPU load
> > and interrupt frequency.
> > 
> > This patch create one SPI transfer with all fields and not optional retires. If
> > bounce anomaly was detected, we will make more transfer if needed.
> > 
> > Without this patch, we will get about 10% CPU load on iMX6S on pen-down event.
> > For example by holding stylus on the screen.
> > 
> > With this patch, depending in the amount of retries, the CPU load will
> > be 1% with "ti,debounce-rep = <3>".
> > 
> > One buffer transfer allows us to use PIO FIFO or DMA engine, depending
> > on the platform.
> > 
> > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> 
> Applied, thank you.

I can't find this patch in your git repository. Should I rebase it
against latest git and resend it?

Regards,
Oleksij
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