charger: tps65090: Allow charger module to be used when no irq

On the ARM Chromebook tps65090 has two masters: the AP (the main
processor running linux) and the EC (the embedded controller). The AP
is allowed to mess with FETs but the EC is in charge of charge control.

The tps65090 interupt line is routed to both the AP and the EC, which
can cause quite a headache. Having two people adjusting masks and
acking interrupts is a recipe for disaster.

In the shipping kernel we had a hack to have the AP pay attention to
the IRQ but not to ack it. It also wasn't supposed to configure the
IRQ in any way. That hack allowed us to detect when the device was
charging without messing with the EC's state.

The current tps65090 infrastructure makes the above difficult, and it
was a bit of a hack to begin with. Rather than uglify the driver to
support it, just extend the driver's existing notion of "no irq" to
the charger. This makes the charger code poll every 2 seconds for AC
detect, which is sufficient.

For proper functioning, requires (mfd: tps65090: Don't tell child
devices we have an IRQ if we don't). If we don't have that patch
we'll simply fail to probe on devices without an interrupt (just like
we did before this patch).

Signed-off-by: Doug Anderson <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Tested-by: Javier Martinez Canillas <[e-mail]>
[[e-mail]: Use -ENXIO instead of NO_IRQ for missing interrupt,
since NO_IRQ is not available on all architectures.]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/tps65090-charger.c

···
  */
 #include <linux/delay.h>
 #include <linux/err.h>
+#include <linux/freezer.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
+#include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
···
 #define TPS65090_VACG		BIT(1)
 #define TPS65090_NOITERM	BIT(5)
 
+#define POLL_INTERVAL		(HZ * 2)	/* Used when no irq */
+
 struct tps65090_charger {
 	struct	device	*dev;
 	int	ac_online;
 	int	prev_ac_online;
 	int	irq;
+	struct task_struct	*poll_task;
+	bool			passive_mode;
 	struct power_supply	ac;
 	struct tps65090_platform_data *pdata;
 };
···
 static int tps65090_low_chrg_current(struct tps65090_charger *charger)
 {
 	int ret;
+
+	if (charger->passive_mode)
+		return 0;
 
 	ret = tps65090_write(charger->dev->parent, TPS65090_REG_CG_CTRL5,
 			TPS65090_NOITERM);
···
 {
 	int ret;
 	uint8_t ctrl0 = 0;
+
+	if (charger->passive_mode)
+		return 0;
 
 	ret = tps65090_read(charger->dev->parent, TPS65090_REG_CG_CTRL0,
 			    &ctrl0);
···
 {
 	uint8_t intrmask = 0;
 	int ret;
+
+	if (charger->passive_mode)
+		return 0;
 
 	if (charger->pdata->enable_low_current_chrg) {
 		ret = tps65090_low_chrg_current(charger);
···
 	}
 
 	/* Clear interrupts. */
-	ret = tps65090_write(charger->dev->parent, TPS65090_REG_INTR_STS, 0x00);
-	if (ret < 0) {
-		dev_err(charger->dev, "%s(): Error in writing reg 0x%x\n",
+	if (!charger->passive_mode) {
+		ret = tps65090_write(charger->dev->parent,
+				     TPS65090_REG_INTR_STS, 0x00);
+		if (ret < 0) {
+			dev_err(charger->dev,
+				"%s(): Error in writing reg 0x%x\n",
 				__func__, TPS65090_REG_INTR_STS);
+		}
 	}
 
 	if (charger->prev_ac_online != charger->ac_online)
···
 
 	return pdata;
 
+}
+
+static int tps65090_charger_poll_task(void *data)
+{
+	set_freezable();
+
+	while (!kthread_should_stop()) {
+		schedule_timeout_interruptible(POLL_INTERVAL);
+		try_to_freeze();
+		tps65090_charger_isr(-1, data);
+	}
+	return 0;
 }
 
 static int tps65090_charger_probe(struct platform_device *pdev)
···
 	}
 
 	irq = platform_get_irq(pdev, 0);
-	if (irq <= 0) {
-		dev_warn(&pdev->dev, "Unable to get charger irq = %d\n", irq);
-		ret = irq;
-		goto fail_unregister_supply;
-	}
-
+	if (irq < 0)
+		irq = -ENXIO;
 	cdata->irq = irq;
-
-	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
-		tps65090_charger_isr, 0, "tps65090-charger", cdata);
-	if (ret) {
-		dev_err(cdata->dev, "Unable to register irq %d err %d\n", irq,
-			ret);
-		goto fail_unregister_supply;
-	}
 
 	ret = tps65090_config_charger(cdata);
 	if (ret < 0) {
···
 		power_supply_changed(&cdata->ac);
 	}
 
+	if (irq != -ENXIO) {
+		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+			tps65090_charger_isr, 0, "tps65090-charger", cdata);
+		if (ret) {
+			dev_err(cdata->dev,
+				"Unable to register irq %d err %d\n", irq,
+				ret);
+			goto fail_unregister_supply;
+		}
+	} else {
+		cdata->poll_task = kthread_run(tps65090_charger_poll_task,
+					      cdata, "ktps65090charger");
+		cdata->passive_mode = true;
+		if (IS_ERR(cdata->poll_task)) {
+			ret = PTR_ERR(cdata->poll_task);
+			dev_err(cdata->dev,
+				"Unable to run kthread err %d\n", ret);
+			goto fail_unregister_supply;
+		}
+	}
+
 	return 0;
 
 fail_unregister_supply:
···
 {
 	struct tps65090_charger *cdata = platform_get_drvdata(pdev);
 
+	if (cdata->irq == -ENXIO)
+		kthread_stop(cdata->poll_task);
 	power_supply_unregister(&cdata->ac);
 
 	return 0;