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

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Message-ID: <20180823233424.GE53155@dtor-ws>
Date:   Thu, 23 Aug 2018 16:34:24 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Derek Basehore <dbasehore@...omium.org>,
        Johnny Chuang <johnny.chuang@....com.tw>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        joe@...ches.com, andi@...zian.org, gregkh@...uxfoundation.org,
        James Chen <james.chen@....com.tw>,
        KT Liao <kt.liao@....com.tw>
Subject: Re: [PATCH] Input: elants_i2c - Fix sw reset delays

For real now...

On Thu, Aug 23, 2018 at 04:32:11PM -0700, Dmitry Torokhov wrote:
> 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

-- 
Dmitry