linux-kernel - Re: [PATCH v7 03/48] Input: atmel_mxt_ts - only read messages in mxt_acquire

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Message-ID: <e586b057-1ec1-896e-374e-dba743709806@mentor.com>
Date:   Wed, 18 Mar 2020 22:02:36 +0900
From:   "Wang, Jiada" <jiada_wang@...tor.com>
To:     Dmitry Osipenko <digetx@...il.com>, <jikos@...nel.org>,
        <benjamin.tissoires@...hat.com>, <rydberg@...math.org>,
        <dmitry.torokhov@...il.com>, <nick@...anahar.org>,
        <bsz@...ihalf.com>
CC:     <linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <erosca@...adit-jv.com>, <Andrew_Gabbasov@...tor.com>
Subject: Re: [PATCH v7 03/48] Input: atmel_mxt_ts - only read messages in
 mxt_acquire_irq() when necessary

Hello Dmitry

On 2020/03/18 7:44, Dmitry Osipenko wrote:
> 12.02.2020 11:41, Jiada Wang пишет:
>> 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.
> 
> ...
>> +static int mxt_check_retrigen(struct mxt_data *data)
>> +{
>> +	struct i2c_client *client = data->client;
>> +	int error;
>> +	int val;
>> +
>> +	data->use_retrigen_workaround = false;
>> +
>> +	if (irq_get_trigger_type(data->irq) & IRQF_TRIGGER_LOW)
>> +		return 0;
>> +
>> +	if (data->T18_address) {
>> +		error = __mxt_read_reg(client,
>> +				       data->T18_address + MXT_COMMS_CTRL,
>> +				       1, &val);
>> +		if (error)
>> +			return error;
>> +
>> +		if (val & MXT_COMMS_RETRIGEN)
>> +			return 0;
>> +	}
>> +
>> +	dev_warn(&client->dev, "Enabling RETRIGEN workaround\n");
>> +	data->use_retrigen_workaround = true;
>> +	return 0;
>> +}
> 
> Hello Jiada,
> 
> I'm seeing "Enabling RETRIGEN workaround" message with the following
> device-tree entry:
> 
> touchscreen@4c {
> 	compatible = "atmel,maxtouch";
> 	reg = <0x4c>;
> 
> 	interrupt-parent = <&gpio>;
> 	interrupts = <TEGRA_GPIO(V, 6) IRQ_TYPE_LEVEL_LOW>;
> 
> 	reset-gpios = <&gpio TEGRA_GPIO(Q, 7) GPIO_ACTIVE_HIGH>;
> };
> 
> This happens because data->irq is NULL. Please fix it, thanks in advance.
Thanks for reporting this issue,
I will fix this issue in v8 patch-set

Thanks,
Jiada
>