Re: [PATCH 1/3 v2] Input: atmel_mxt_ts - Make wait-after-reset period compatible with all chips

[Iiro Valkonen <iiro.valkonen@atmel.com>]

Hello,

On 07/05/2011 04:07 AM, Joonyoung Shim wrote:
> Hi,
> 
> On 2011-07-04 오후 9:57, Iiro Valkonen wrote:
>> The delay before the chip can be accessed after reset varies between different
>> chips in maXTouch family. Waiting for 200ms and then monitoring the CHG (chip
>> is ready when the line is low) is guaranteed to work with all chips.
> 
> I wonder 200ms waiting needs indeed, it is very long time.
> If monitoring the CHG line can detect the completion of reset,
> 200ms waiting can be removed?
> 

Yes, 200ms is a bit longish. But it is what we need to guarantee correct
functionality with all chips in all situations. I would prefer to see that
in the mainline version. Anyone worried about the delay could maybe adjust
the value to suit his/her needs, for example with mXT224 you could get away with
using just 65ms, like in the original version. Another option would be to
check the family ID in the driver, and wait just long enough. Drawback with
that is that the driver (possibly) needs updating with every new chip. I'd
like to keep this simple & robust, wait 200ms which works for every current
(and most likely with every upcoming) chip, and take the small delay penalty.

>> @@ -828,6 +829,12 @@ static int mxt_initialize(struct mxt_data *data)
>>       mxt_write_object(data, MXT_GEN_COMMAND,
>>               MXT_COMMAND_RESET, 1);
>>       msleep(MXT_RESET_TIME);
>> +    while ((reset_timeout++<= 100)&&  data->pdata->read_chg())
> 
> If pdata->read_chg is NULL?
> 

Hopefully it'll never be, but I'll add a check.

Thank you for the comments.

-- 
Iiro
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html