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Message-ID: <c41e011b-16de-d49f-21d4-0abd81841324@kernel.org>
Date:   Wed, 13 Apr 2022 13:38:48 +0300
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Subject: Re: [PATCH RFC] usb: typec: tipd: Add support for polling interrupts
 status when interrupt line is not connected
Content-Language: en-US
To:     Aswath Govindraju <a-govindraju@ti.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc:     Vignesh Raghavendra <vigneshr@ti.com>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sven Peter <sven@svenpeter.dev>,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>,
        Hector Martin <marcan@marcan.st>,
        Saranya Gopal <saranya.gopal@intel.com>,
        Jens Axboe <axboe@kernel.dk>, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220412145059.4717-1-a-govindraju@ti.com>
 <YlaZIual4Fa/a81I@kuha.fi.intel.com>
 <5672af5d-d4a9-08ab-0594-7da57cd0972b@ti.com>
From:   Roger Quadros <rogerq@kernel.org>
In-Reply-To: <5672af5d-d4a9-08ab-0594-7da57cd0972b@ti.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi Aswath,

On 13/04/2022 13:02, Aswath Govindraju wrote:
> Hi Heikki,
> 
> On 13/04/22 15:04, Heikki Krogerus wrote:
>> Hi Aswath,
>>
>> On Tue, Apr 12, 2022 at 08:20:58PM +0530, Aswath Govindraju wrote:
>>> In some cases the interrupt line from the pd controller may not be
>>> connected. In these cases, poll the status of various events.
>>
>> Well, if the alert/interrupt line is not connected anywhere, then
>> polling is the only way to go. I'm fine with that, but the driver
>> really should be told that there is no interrupt. Using polling
>> whenever request_threaded_irq() returns -EINVAL is wrong. We really
>> should not even attempt to request the interrupt if there is no
>> interrupt for the device.
>>
>> Isn't there any way you can get that information from DT? Or how is
>> the device enumerated in your case?
>>
> 
> Would checking if (client->irq) field is populated, to decide between
> polling and interrupts be a good approach?

'interrupt' and 'interrupt-names' are required properties in DT binding doc
Documentation/devicetree/bindings/usb/ti,tps6598x.yaml

You will need to add a new property to indicate that polling mode must be used
and then interrupt properties become optional.

> 
> I am sorry but I did not understand what you meant by device getting
> enumerated. The device is on an I2C bus and gets enumerated based on the
> I2C address provided. The device does not have I2C_IRQ line connected,
> in my case.

I think he meant whether you are using device tree or something else.

> 
> Thanks,
> Aswath
> 
>>> Suggested-by: Roger Quadros <rogerq@kernel.org>
>>> Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
>>> ---
>>>  drivers/usb/typec/tipd/core.c | 90 ++++++++++++++++++++++++++++++++---
>>>  1 file changed, 83 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/usb/typec/tipd/core.c b/drivers/usb/typec/tipd/core.c
>>> index 16b4560216ba..fa52d2067d6d 100644
>>> --- a/drivers/usb/typec/tipd/core.c
>>> +++ b/drivers/usb/typec/tipd/core.c
>>> @@ -15,6 +15,8 @@
>>>  #include <linux/interrupt.h>
>>>  #include <linux/usb/typec.h>
>>>  #include <linux/usb/role.h>
>>> +#include <linux/workqueue.h>
>>> +#include <linux/devm-helpers.h>
>>>  
>>>  #include "tps6598x.h"
>>>  #include "trace.h"
>>> @@ -93,6 +95,8 @@ struct tps6598x {
>>>  	struct power_supply *psy;
>>>  	struct power_supply_desc psy_desc;
>>>  	enum power_supply_usb_type usb_type;
>>> +
>>> +	struct delayed_work wq_poll;
>>>  };
>>>  
>>>  static enum power_supply_property tps6598x_psy_props[] = {
>>> @@ -473,9 +477,8 @@ static void tps6598x_handle_plug_event(struct tps6598x *tps, u32 status)
>>>  	}
>>>  }
>>>  
>>> -static irqreturn_t cd321x_interrupt(int irq, void *data)
>>> +static int cd321x_handle_interrupt_status(struct tps6598x *tps)
>>>  {
>>> -	struct tps6598x *tps = data;
>>>  	u64 event;
>>>  	u32 status;
>>>  	int ret;
>>> @@ -513,14 +516,45 @@ static irqreturn_t cd321x_interrupt(int irq, void *data)
>>>  err_unlock:
>>>  	mutex_unlock(&tps->lock);
>>>  
>>> +	if (ret)
>>> +		return ret;
>>> +
>>>  	if (event)
>>> -		return IRQ_HANDLED;
>>> -	return IRQ_NONE;
>>> +		return 0;
>>> +	return 1;
>>>  }
>>>  
>>> -static irqreturn_t tps6598x_interrupt(int irq, void *data)
>>> +static irqreturn_t cd321x_interrupt(int irq, void *data)
>>>  {
>>>  	struct tps6598x *tps = data;
>>> +	int ret;
>>> +
>>> +	ret = cd321x_handle_interrupt_status(tps);
>>> +	if (ret)
>>> +		return IRQ_NONE;
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>> +/* Time interval for Polling */
>>> +#define POLL_INTERVAL   500 /* msecs */
>>> +static void cd321x_poll_work(struct work_struct *work)
>>> +{
>>> +	struct tps6598x *tps = container_of(to_delayed_work(work),
>>> +					    struct tps6598x, wq_poll);
>>> +	int ret;
>>> +
>>> +	ret = cd321x_handle_interrupt_status(tps);
>>> +	/*
>>> +	 * If there is an error while reading the interrupt registers
>>> +	 * then stop polling else, schedule another poll work item
>>> +	 */
>>> +	if (!(ret < 0))
>>> +		queue_delayed_work(system_power_efficient_wq,
>>> +				   &tps->wq_poll, msecs_to_jiffies(POLL_INTERVAL));
>>> +}
>>> +
>>> +static int tps6598x_handle_interrupt_status(struct tps6598x *tps)
>>> +{
>>>  	u64 event1;
>>>  	u64 event2;
>>>  	u32 status;
>>> @@ -561,9 +595,39 @@ static irqreturn_t tps6598x_interrupt(int irq, void *data)
>>>  err_unlock:
>>>  	mutex_unlock(&tps->lock);
>>>  
>>> +	if (ret)
>>> +		return ret;
>>> +
>>>  	if (event1 | event2)
>>> -		return IRQ_HANDLED;
>>> -	return IRQ_NONE;
>>> +		return 0;
>>> +	return 1;
>>> +}
>>> +
>>> +static irqreturn_t tps6598x_interrupt(int irq, void *data)
>>> +{
>>> +	struct tps6598x *tps = data;
>>> +	int ret;
>>> +
>>> +	ret = tps6598x_handle_interrupt_status(tps);
>>> +	if (ret)
>>> +		return IRQ_NONE;
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>> +static void tps6598x_poll_work(struct work_struct *work)
>>> +{
>>> +	struct tps6598x *tps = container_of(to_delayed_work(work),
>>> +					    struct tps6598x, wq_poll);
>>> +	int ret;
>>> +
>>> +	ret = tps6598x_handle_interrupt_status(tps);
>>> +	/*
>>> +	 * If there is an error while reading the interrupt registers
>>> +	 * then stop polling else, schedule another poll work item
>>> +	 */
>>> +	if (!(ret < 0))
>>> +		queue_delayed_work(system_power_efficient_wq,
>>> +				   &tps->wq_poll, msecs_to_jiffies(POLL_INTERVAL));
>>>  }
>>>  
>>>  static int tps6598x_check_mode(struct tps6598x *tps)
>>> @@ -704,6 +768,7 @@ static int devm_tps6598_psy_register(struct tps6598x *tps)
>>>  static int tps6598x_probe(struct i2c_client *client)
>>>  {
>>>  	irq_handler_t irq_handler = tps6598x_interrupt;
>>> +	work_func_t work_poll_handler = tps6598x_poll_work;
>>>  	struct device_node *np = client->dev.of_node;
>>>  	struct typec_capability typec_cap = { };
>>>  	struct tps6598x *tps;
>>> @@ -748,6 +813,7 @@ static int tps6598x_probe(struct i2c_client *client)
>>>  			APPLE_CD_REG_INT_PLUG_EVENT;
>>>  
>>>  		irq_handler = cd321x_interrupt;
>>> +		work_poll_handler = cd321x_poll_work;
>>>  	} else {
>>>  		/* Enable power status, data status and plug event interrupts */
>>>  		mask1 = TPS_REG_INT_POWER_STATUS_UPDATE |
>>> @@ -846,6 +912,16 @@ static int tps6598x_probe(struct i2c_client *client)
>>>  					irq_handler,
>>>  					IRQF_SHARED | IRQF_ONESHOT,
>>>  					dev_name(&client->dev), tps);
>>> +	if (ret == -EINVAL) {
>>> +		dev_warn(&client->dev, "Unable to find the interrupt, switching to polling\n");
>>> +		ret = devm_delayed_work_autocancel(tps->dev, &tps->wq_poll, work_poll_handler);
>>> +		if (ret)
>>> +			dev_err(&client->dev, "error while initializing workqueue\n");
>>> +		else
>>> +			queue_delayed_work(system_power_efficient_wq, &tps->wq_poll,
>>> +					   msecs_to_jiffies(POLL_INTERVAL));
>>> +	}
>>> +
>>>  	if (ret) {
>>>  		tps6598x_disconnect(tps, 0);
>>>  		typec_unregister_port(tps->port);
>>
>> thanks,
>>
> 
> 

--
cheers,
-roger