linux-kernel - Re: [PATCH v1 03/63] Input: atmel_mxt_ts - only read messages in mxt_acquire

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Message-ID: <cab8d0cd-21ec-3844-5e4f-eb5b582aa432@mentor.com>
Date:   Thu, 22 Aug 2019 12:37:12 +0900
From:   Jiada Wang <jiada_wang@...tor.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:     <nick@...anahar.org>, <linux-input@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <george_davis@...tor.com>
Subject: Re: [PATCH v1 03/63] Input: atmel_mxt_ts - only read messages in
 mxt_acquire_irq() when necessary

Hi

On 2019/08/22 2:54, Dmitry Torokhov wrote:
> On Wed, Aug 21, 2019 at 10:26:31PM +0900, Jiada Wang wrote:
>> Hi Dmitry
>>
>> On 2019/08/17 2:16, Dmitry Torokhov wrote:
>>> On Fri, Aug 16, 2019 at 05:28:52PM +0900, Jiada Wang wrote:
>>>> From: Nick Dyer <nick.dyer@...ev.co.uk>
>>>>
>>>> The workaround of reading all messages until an invalid is received is a
>>>> way of forcing the CHG line high, which means that when using
>>>> edge-triggered interrupts the interrupt can be acquired.
>>>>
>>>> With level-triggered interrupts the workaround is unnecessary.
>>>>
>>>> Also, most recent maXTouch chips have a feature called RETRIGEN which, when
>>>> enabled, reasserts the interrupt line every cycle if there are messages
>>>> waiting. This also makes the workaround unnecessary.
>>>>
>>>> Note: the RETRIGEN feature is only in some firmware versions/chips, it's
>>>> not valid simply to enable the bit.
>>>
>>> Instead of trying to work around of misconfiguration for IRQ/firmware,
>>> can we simply error out of probe if we see a level interrupt with
>>> !RETRIGEN firmware?
>>>
>> I think for old firmwares, which doesn't support RETRIGEN feature, this
>> workaround is needed, otherwise we will break all old firmwares, which
>> configured with edge-triggered IRQ
> 
> Do you know if there are any? I know Chrome OS firmware have RETRIGEN
> activated and they are pretty old (original Pixel is from 2013). But if
> we indeed have devices with edge interrupt and old not firmware that
> does not retrigger, I guess we'll have to keep it...
> 

Honestly I don't know firmwares/chips which don't support RETRIGEN feature.

BUT Dyer originally authored this patch in 2012, I assume here "old" 
firmware/chips means, those before 2012.


Thanks,
Jiada

> Thanks.
>