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SubjectRe: [PATCH 1/4] mfd: twl6030-irq: migrate to IRQ threaded handler
On Tue, 23 Jul 2013, Grygorii Strashko wrote:

> From: Naga Venkata Srikanth V <vnv.srikanth@samsung.com>
>
> 1) Removed request_irq() and replaced it with request_threaded_irq().
>
> 2) Removed generic_handle_irq() and replaced it with
> handle_nested_irq().
> Handling of these interrupts is nested, as we are handling an
> interrupt (for e.g rtc, mmc1) when we are still servicing TWL irq.
>
> 3) Removed I2C read-retry logic for the case when twl_i2c_read() is
> failed inside IRQ handler - there is no sense to do that, so just report
> an error and return.
>
> Signed-off-by: Naga Venkata Srikanth V <vnv.srikanth@samsung.com>
> Signed-off-by: Oleg_Kosheliev <oleg.kosheliev@ti.com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
> ---
> drivers/mfd/twl6030-irq.c | 146 +++++++++++++++------------------------------
> 1 file changed, 49 insertions(+), 97 deletions(-)

Besides the points I mention below I like the way this patch is
going.

> diff --git a/drivers/mfd/twl6030-irq.c b/drivers/mfd/twl6030-irq.c
> index 277a8db..b6030d9 100644
> --- a/drivers/mfd/twl6030-irq.c
> +++ b/drivers/mfd/twl6030-irq.c
> @@ -90,7 +90,6 @@ static unsigned twl6030_irq_base;
> static int twl_irq;
> static bool twl_irq_wake_enabled;
>
> -static struct completion irq_event;
> static atomic_t twl6030_wakeirqs = ATOMIC_INIT(0);
>
> static int twl6030_irq_pm_notifier(struct notifier_block *notifier,
> @@ -131,95 +130,57 @@ static struct notifier_block twl6030_irq_pm_notifier_block = {
> };
>
> /*
> - * This thread processes interrupts reported by the Primary Interrupt Handler.
> - */
> -static int twl6030_irq_thread(void *data)
> +* Threaded irq handler for the twl6030 interrupt.
> +* We query the interrupt controller in the twl6030 to determine
> +* which module is generating the interrupt request and call
> +* handle_nested_irq for that module.
> +*/
> +static irqreturn_t twl6030_irq_thread(int irq, void *data)
> {
> - long irq = (long)data;
> - static unsigned i2c_errors;
> - static const unsigned max_i2c_errors = 100;
> - int ret;
> -
> - while (!kthread_should_stop()) {
> - int i;
> - union {
> + int i, ret;
> + union {
> u8 bytes[4];
> u32 int_sts;
> - } sts;
> -
> - /* Wait for IRQ, then read PIH irq status (also blocking) */
> - wait_for_completion_interruptible(&irq_event);
> -
> - /* read INT_STS_A, B and C in one shot using a burst read */
> - ret = twl_i2c_read(TWL_MODULE_PIH, sts.bytes,
> - REG_INT_STS_A, 3);
> - if (ret) {
> - pr_warning("twl6030: I2C error %d reading PIH ISR\n",
> - ret);
> - if (++i2c_errors >= max_i2c_errors) {
> - printk(KERN_ERR "Maximum I2C error count"
> - " exceeded. Terminating %s.\n",
> - __func__);
> - break;
> - }
> - complete(&irq_event);
> - continue;
> - }
> -
> + } sts;
>
> + /* read INT_STS_A, B and C in one shot using a burst read */
> + ret = twl_i2c_read(TWL_MODULE_PIH, sts.bytes, REG_INT_STS_A, 3);
> + if (ret) {
> + pr_warn("%s: I2C error %d reading PIH ISR\n", __func__, ret);

Does the user really care which function we're returning from.

Would it be better if you replace '__func__' with the device name?

> + return IRQ_HANDLED;
> + }
>
> - sts.bytes[3] = 0; /* Only 24 bits are valid*/
> + sts.bytes[3] = 0; /* Only 24 bits are valid*/
>
> - /*
> - * Since VBUS status bit is not reliable for VBUS disconnect
> - * use CHARGER VBUS detection status bit instead.
> - */
> - if (sts.bytes[2] & 0x10)
> - sts.bytes[2] |= 0x08;
> + /*
> + * Since VBUS status bit is not reliable for VBUS disconnect
> + * use CHARGER VBUS detection status bit instead.
> + */
> + if (sts.bytes[2] & 0x10)
> + sts.bytes[2] |= 0x08;
>
> - for (i = 0; sts.int_sts; sts.int_sts >>= 1, i++) {
> - local_irq_disable();
> - if (sts.int_sts & 0x1) {
> - int module_irq = twl6030_irq_base +
> + for (i = 0; sts.int_sts; sts.int_sts >>= 1, i++)
> + if (sts.int_sts & 0x1) {

I'm a little confused by this. Where does sts.int_sts come from?

> + int module_irq = twl6030_irq_base +
> twl6030_interrupt_mapping[i];
> - generic_handle_irq(module_irq);
> -
> - }
> - local_irq_enable();
> + handle_nested_irq(module_irq);
> + pr_debug("%s: PIH ISR %u, virq%u\n",
> + __func__, i, module_irq);
> }
>
> - /*
> - * NOTE:
> - * Simulation confirms that documentation is wrong w.r.t the
> - * interrupt status clear operation. A single *byte* write to
> - * any one of STS_A to STS_C register results in all three
> - * STS registers being reset. Since it does not matter which
> - * value is written, all three registers are cleared on a
> - * single byte write, so we just use 0x0 to clear.
> - */
> - ret = twl_i2c_write_u8(TWL_MODULE_PIH, 0x00, REG_INT_STS_A);
> - if (ret)
> - pr_warning("twl6030: I2C error in clearing PIH ISR\n");
> -
> - enable_irq(irq);
> - }
> -
> - return 0;
> -}
> + /*
> + * NOTE:
> + * Simulation confirms that documentation is wrong w.r.t the
> + * interrupt status clear operation. A single *byte* write to
> + * any one of STS_A to STS_C register results in all three
> + * STS registers being reset. Since it does not matter which
> + * value is written, all three registers are cleared on a
> + * single byte write, so we just use 0x0 to clear.
> + */
> + ret = twl_i2c_write_u8(TWL_MODULE_PIH, 0x00, REG_INT_STS_A);
> + if (ret)
> + pr_warn("twl6030: I2C error in clearing PIH ISR\n");
>
> -/*
> - * handle_twl6030_int() is the desc->handle method for the twl6030 interrupt.
> - * This is a chained interrupt, so there is no desc->action method for it.
> - * Now we need to query the interrupt controller in the twl6030 to determine
> - * which module is generating the interrupt request. However, we can't do i2c
> - * transactions in interrupt context, so we must defer that work to a kernel
> - * thread. All we do here is acknowledge and mask the interrupt and wakeup
> - * the kernel thread.
> - */
> -static irqreturn_t handle_twl6030_pih(int irq, void *devid)
> -{
> - disable_irq_nosync(irq);
> - complete(devid);
> return IRQ_HANDLED;
> }
>
> @@ -351,7 +312,6 @@ int twl6030_init_irq(struct device *dev, int irq_num)
> {
> struct device_node *node = dev->of_node;
> int nr_irqs, irq_base, irq_end;
> - struct task_struct *task;
> static struct irq_chip twl6030_irq_chip;
> int status = 0;
> int i;
> @@ -396,36 +356,25 @@ int twl6030_init_irq(struct device *dev, int irq_num)
> irq_set_chip_and_handler(i, &twl6030_irq_chip,
> handle_simple_irq);
> irq_set_chip_data(i, (void *)irq_num);
> + irq_set_nested_thread(i, true);
> activate_irq(i);
> }
>
> - dev_info(dev, "PIH (irq %d) chaining IRQs %d..%d\n",
> - irq_num, irq_base, irq_end);
> + dev_info(dev, "PIH (irq %d) nested IRQs %d..%d\n",
> + irq_num, irq_base, irq_end);
>
> /* install an irq handler to demultiplex the TWL6030 interrupt */
> - init_completion(&irq_event);
> -
> - status = request_irq(irq_num, handle_twl6030_pih, 0, "TWL6030-PIH",
> - &irq_event);
> + status = request_threaded_irq(irq_num, NULL, twl6030_irq_thread,
> + IRQF_ONESHOT, "TWL6030-PIH", NULL);
> if (status < 0) {
> dev_err(dev, "could not claim irq %d: %d\n", irq_num, status);
> goto fail_irq;
> }
>
> - task = kthread_run(twl6030_irq_thread, (void *)irq_num, "twl6030-irq");
> - if (IS_ERR(task)) {
> - dev_err(dev, "could not create irq %d thread!\n", irq_num);
> - status = PTR_ERR(task);
> - goto fail_kthread;
> - }
> -
> twl_irq = irq_num;
> register_pm_notifier(&twl6030_irq_pm_notifier_block);
> return irq_base;
>
> -fail_kthread:
> - free_irq(irq_num, &irq_event);
> -
> fail_irq:
> for (i = irq_base; i < irq_end; i++)
> irq_set_chip_and_handler(i, NULL, NULL);
> @@ -437,10 +386,13 @@ int twl6030_exit_irq(void)
> {
> unregister_pm_notifier(&twl6030_irq_pm_notifier_block);
>
> - if (twl6030_irq_base) {
> + if (!twl6030_irq_base) {
> pr_err("twl6030: can't yet clean up IRQs?\n");
> return -ENOSYS;
> }
> +
> + free_irq(twl_irq, NULL);
> +

If request_threaded_irq() fails, isn't there a chance that
twl6030_irq_base will be allocated, but twl_irq will still be
undefined?

> return 0;
> }
>

--
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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