linux-kernel - Re: [PATCH v2] extcon: usbc-tusb320: make sure the state is initialized on probe

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Message-ID: <0cfd0141-954a-d455-b3cc-5eda8c275e01@axentia.se>
Date:   Tue, 10 Jan 2023 16:01:14 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     Chanwoo Choi <cwchoi00@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Michael Auchter <michael.auchter@...com>
Subject: Re: [PATCH v2] extcon: usbc-tusb320: make sure the state is
 initialized on probe

Hi!

2023-01-10 at 15:14, Chanwoo Choi wrote:
> Hi,
> 
> On 22. 12. 13. 07:36, Peter Rosin wrote:
>> When the port is connected at boot, there is not necessarily
>> an interrupt flagged in the interrupt status register, causing
>> the IRQ handler to bail out early without reading the state when
>> it is invoked directly from probe.
>>
>> Add a flag that overrides the interrupt status register and reads
>> the state regardless during probe.
>>
>> Fixes: 06bc4ca115cd ("extcon: Add driver for TI TUSB320")
>> Signed-off-by: Peter Rosin <peda@...ntia.se>
>> ---
>>  drivers/extcon/extcon-usbc-tusb320.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> Hi!
>>
>> This is basically a resend of v1, the patch has simply been adapted
>> to fit after the driver changes for type-c support.
>>
>> Version 1 of the patch, with its brief "discussion", is here:
>> https://lore.kernel.org/lkml/ab1ad93b-4d39-8863-9704-da779fc4c426@axentia.se/
>>
>> I cannot see how the patch can possibly affect detection of connector
>> changes *after* 'priv->initialized = true', so the comment from Chanwoo
>> Choi is still a mystery to me. The patch is about what happens *before*
>> 'priv->initialized = true', i.e. when the IRQ handler is called directly
>> during probe. There is no change in behavior after the statement
>> 'priv->initialized = true', and IRQs are handled exactly as before once
>> past that point.
>>
>> Please look at this patch again.
>>
>> Cheers,
>> Peter
>>
>> diff --git a/drivers/extcon/extcon-usbc-tusb320.c b/drivers/extcon/extcon-usbc-tusb320.c
>> index 2a120d8d3c27..dc586e5e3c65 100644
>> --- a/drivers/extcon/extcon-usbc-tusb320.c
>> +++ b/drivers/extcon/extcon-usbc-tusb320.c
>> @@ -78,6 +78,7 @@ struct tusb320_priv {
>>  	struct typec_capability	cap;
>>  	enum typec_port_type port_type;
>>  	enum typec_pwr_opmode pwr_opmode;
>> +	bool initialized;
>>  };
>>  
>>  static const char * const tusb_attached_states[] = {
>> @@ -323,7 +324,7 @@ static irqreturn_t tusb320_irq_handler(int irq, void *dev_id)
>>  		return IRQ_NONE;
>>  	}
>>  
>> -	if (!(reg & TUSB320_REG9_INTERRUPT_STATUS))
>> +	if (priv->initialized && !(reg & TUSB320_REG9_INTERRUPT_STATUS))
>>  		return IRQ_NONE;
>>  
>>  	tusb320_extcon_irq_handler(priv, reg);
>> @@ -479,6 +480,8 @@ static int tusb320_probe(struct i2c_client *client,
>>  		 */
>>  		tusb320_irq_handler(client->irq, priv);
>>  
>> +	priv->initialized = true;
>> +
>>  	ret = devm_request_threaded_irq(priv->dev, client->irq, NULL,
>>  					tusb320_irq_handler,
>>  					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> 
> I think that if priv->initialized=true on probe step,
> tusb32_irq_handler return the always IRQ_NONE
> because priv->initialized is never changed to false.

The new behavior is to never return early when priv->initialized is
false. When priv->initialized is true, the old behavior is retained
through the right hand side of the && operator.

> Is it right to keep the 'priv->initialized=true' always?

Yes.

However, this patch is no longer needed. I have since noticed that
the problem was later solved by Marek Vasut with
581c848b610d ("extcon: usbc-tusb320: Update state on probe even if no IRQ pending")
which does pretty much the same thing as this patch, but with
force_update as a function argument (and inverted logic, so
"if (!forced_update && ...)" in the above if-test instead of
"if (priv->initialized && ...)".)

Cheers,
Peter