linux-kernel - Re: [PATCH] Input: elants_i2c

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Date:   Thu, 23 Aug 2018 16:32:11 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Derek Basehore <dbasehore@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        joe@...ches.com, andi@...zian.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH] Input: elants_i2c - Fix sw reset delays

Let's add Elan folks to the discussion.

On Thu, Aug 23, 2018 at 04:30:28PM -0700, Dmitry Torokhov wrote:
> Hi Derek,
> 
> On Thu, Aug 23, 2018 at 04:10:13PM -0700, Derek Basehore wrote:
> > We only need to wait 10ms instead of 30ms before starting fastboot or
> > sending IAP on the touchscreen. Also, instead of delaying everytime
> > sw_reset is called, this delays 10ms in the function that starts
> > fastboot. There's also an explicit 20ms delay before sending IAP when
> > updating the firmware, so no additional delay is needed there. This
> > change also has the benefit of not delaying when wakeup is enabled
> > during suspend. This is because sw_reset is called, yet fastboot
> > isn't.
> > 
> > Change-Id: I9e3019720186ba0023891fafeb4fe3d2510e454b
> 
> This is not needed ;)
> 
> > Signed-off-by: Derek Basehore <dbasehore@...omium.org>
> > ---
> >  drivers/input/touchscreen/elants_i2c.c | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/input/touchscreen/elants_i2c.c b/drivers/input/touchscreen/elants_i2c.c
> > index d21ca39b0fdb..18ce04ba0173 100644
> > --- a/drivers/input/touchscreen/elants_i2c.c
> > +++ b/drivers/input/touchscreen/elants_i2c.c
> > @@ -284,12 +284,6 @@ static int elants_i2c_sw_reset(struct i2c_client *client)
> >  		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);
> > -
> >  	return 0;
> >  }
> >  
> > @@ -500,6 +494,12 @@ static int elants_i2c_fastboot(struct i2c_client *client)
> >  	const u8 boot_cmd[] = { 0x4D, 0x61, 0x69, 0x6E };
> >  	int error;
> >  
> > +	/*
> > +	 * We should wait at least 10 msec (but no more than 40) before sending
> > +	 * fastboot command to the device.
> > +	 */
> > +	usleep_range(10 * 1000, 11 * 1000);
> > +
> >  	error = elants_i2c_send(client, boot_cmd, sizeof(boot_cmd));
> >  	if (error) {
> >  		dev_err(&client->dev, "boot failed: %d\n", error);
> > @@ -643,6 +643,10 @@ static int elants_i2c_do_update_firmware(struct i2c_client *client,
> >  			dev_err(&client->dev, "Failed close idle: %d\n", error);
> >  		msleep(60);
> >  		elants_i2c_sw_reset(client);
> > +		/*
> > +		 * We should wait at least 10 msec (but no more than 40) before
> > +		 * sending IAP command to the device.
> > +		 */
> >  		msleep(20);
> 
> So the original comment was talking about timing on fastboot or IAP
> command, but the original code had 50 msec wait here (30 from
> elants_i2c_sw_reset plus the 20), thus already violating 40 msec rule
> for IAP. Unless Elan folks can confirm it is OK to reduce the wait here
> I'd prefer we kept it at 50. Firmware update is does not happen that
> often anyway.
> 
> Thanks.
> 
> -- 
> Dmitry

-- 
Dmitry