linux-kernel - Re: [PATCH v1] Input: elants_i2c: Add Elan touchscreen support

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Message-ID: <20141120175158.GB14798@dtor-glaptop>
Date:	Thu, 20 Nov 2014 09:51:58 -0800
From:	'Dmitry Torokhov' <dmitry.torokhov@...il.com>
To:	ELAN 劉嘉駿 <scott.liu@....com.tw>
Cc:	'Oliver Neukum' <oneukum@...e.de>, linux-kernel@...r.kernel.org,
	linux-input@...r.kernel.org,
	'Vincent Wang' <vincent.wang@....com.tw>,
	'Jeff Chuang' <jeff.chuang@....com.tw>,
	'Benson Leung' <bleung@...omium.org>,
	'Benjamin Tissoires' <benjamin.tissoires@...il.com>,
	'Henrik Rydberg' <rydberg@...omail.se>,
	'David Herrmann' <dh.herrmann@...il.com>
Subject: Re: [PATCH v1] Input: elants_i2c: Add Elan touchscreen support

On Thu, Nov 20, 2014 at 08:25:15PM +0800, ELAN 劉嘉駿 wrote:
> 
> Hi Oliver:
> 
> -----Original Message-----
> From: Oliver Neukum [mailto:oneukum@...e.de] 
> Sent: Thursday, November 20, 2014 6:32 PM
> To: Dmitry Torokhov
> Cc: scott; linux-kernel@...r.kernel.org; linux-input@...r.kernel.org; Vincent Wang; Jeff Chuang; Benson Leung; Benjamin Tissoires; Henrik Rydberg; David Herrmann
> Subject: Re: [PATCH v1] Input: elants_i2c: Add Elan touchscreen support
> 
> 
> 
> > +static int elants_i2c_sw_reset(struct i2c_client *client) {
> > +       const u8 soft_rst_cmd[] = { 0x77, 0x77, 0x77, 0x77 };
> > +       int error;
> > +
> > +       error = elants_i2c_send(client, soft_rst_cmd,
> > +                               sizeof(soft_rst_cmd));
> > +       if (error) {
> > +               dev_err(&client->dev, "software reset failed: %d\n",
> > error);
> > +               return error;
> > +       }
> > +
> > +       /*
> > +        * We should wait at least 10 msec (but no more than 40)
> > before
> > +        * sending fastboot or IAP command to the device.
> > +        */
> > +       msleep(30);
> 
> If timing is critical in both ways, you should take our guarantee if sufficient sleep. I suggest you sleep 11msecs.
> 
> Sorry, this is our firmware tricky but it should be sleep longer than 30ms. Actually 70ms.
> (Dmitry, I need to modify this delay time to 70ms. Sorry for the changed over and over again; 
> 	because we consider big sensor solution which need to use more ICs and need more longer delay)
> 

Wait, before you said that upper bound is critical, otherwise the device will
ignore the next command and will not enter IAP mode. So what will happen if we
increase the wait to 70 msecs and use the driver with smaller sensors?

Thanks.

-- 
Dmitry
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