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

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Date:   Wed, 18 Mar 2020 01:44:12 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Jiada Wang <jiada_wang@...tor.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

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.