Re: [PATCH] input: egalax_ts: optmize driver for more fluency touch feelling

Hi Dimitry,

2011/12/12 Dmitry Torokhov [off-list ref]

Hi Zhang,

On Wed, Dec 07, 2011 at 05:10:02PM +0800, Zhang Jiejing wrote:

quoted

egalax_ts use threaded_irq to report touch event, it will wake up the
irq thread and stop the thread irq after process one touch event, so
even user touch the screen very fast, the fastest event report speed
is depends on the scheduler, so the event reported is a uniform speed.

I am not sure what you mean by "the event reported is a uniform speed"
but since I2C operations generally sleep you are at the mercy of
scheduler anyways. But since IRQ thread is a real-time one it should get
scheduled immediately.

I'm using 2.6.38 kernel and Android 4.0 and with a Freescale ARM
A9(1.0GHz) Soc doing this test, but in my test, if I sweep on the
touch screen with very fast speed, my UI can't move as fast as my
finger,
I first suspect our GPU not powerful to drive UI, but after test with
USB mouse doing same sweep operation, the UI was moving quite fast.

So I made this change, after made this change, I can't feed any lay
between finger and the UI animation.
I think the threaded_irq not quite real time.

I checked kernel/irq/handle.c file,
I found in handle_IRQ_event() functin, it will use
wake_up_processs(action->thread);  and the thread was created by
kthread_create() in __setup_irq() function.

I think in this implementation, it will be not so realtime, it depends
on schedule time.

quoted

This patch will let thread irq check the gpio's status, if the gpio
is down, means still have more events, it will not exit the irq handler
and continue process another new event, it can improve user experience.

Does it really or it is your opinion that it would?

As I mentioned in above, I got this result with a real machine and
environment  test.

Also, your change means that the driver can not be stopped/unloaded as
long as user had finger on the touchpad. This would need to be corrected
(but first you need to prove that the change is actually needed).

I need test in the driver unload case and suspend case.

Thanks for you advance.

BR,
Jiejing

Thanks.

--
Dmitry
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