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

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Message-ID: <20180823233028.GC53155@dtor-ws>
Date:   Thu, 23 Aug 2018 16:30:28 -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

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