[PATCH] ab8500_fg.c: only request threaded IRQs when necessary

From: Valentin Rothberg
Date: Mon Feb 16 2015 - 11:36:30 EST


All 5 IRQ handlers of the driver are requested as threaded interrupt
handlers. However, only 1 handler can block. The remaining 4 handlers
defer the actual handling to a workqueue. Hence, 4 of 5 IRQ handlers
have a considerable overhead, since they are executed in a kernel thread
to schedule another kernel thread (workqueue).

This change splits up the 5 interrupt handlers into top halves (_th) and
bottom halves (_bh) and resolves the aforementioned overhead by only
requesting threaded interrupts (i.e., bottom halves) when necessary.

Signed-off-by: Valentin Rothberg <Valentin.Rothberg@xxxxxxx>
---
Due to the lack of hardware I cannot test this change.

I discovered this issue with scripts/coccinelle/misc/irqf_oneshot.cocci since
the threaded interrupts were not requested with IRQF_ONESHOT. By looking closer
I saw the issue of this change.
---
drivers/power/ab8500_fg.c | 46 +++++++++++++++++++++++++++++++++-------------
1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/drivers/power/ab8500_fg.c b/drivers/power/ab8500_fg.c
index c908658..dcd0901 100644
--- a/drivers/power/ab8500_fg.c
+++ b/drivers/power/ab8500_fg.c
@@ -3062,11 +3062,14 @@ static int ab8500_fg_remove(struct platform_device *pdev)
}

/* ab8500 fg driver interrupts and their respective isr */
-static struct ab8500_fg_interrupts ab8500_fg_irq[] = {
+static struct ab8500_fg_interrupts ab8500_fg_irq_th[] = {
{"NCONV_ACCU", ab8500_fg_cc_convend_handler},
{"BATT_OVV", ab8500_fg_batt_ovv_handler},
{"LOW_BAT_F", ab8500_fg_lowbatf_handler},
{"CC_INT_CALIB", ab8500_fg_cc_int_calib_handler},
+};
+
+static struct ab8500_fg_interrupts ab8500_fg_irq_bh[] = {
{"CCEOC", ab8500_fg_cc_data_end_handler},
};

@@ -3194,21 +3197,36 @@ static int ab8500_fg_probe(struct platform_device *pdev)
init_completion(&di->ab8500_fg_started);
init_completion(&di->ab8500_fg_complete);

- /* Register interrupts */
- for (i = 0; i < ARRAY_SIZE(ab8500_fg_irq); i++) {
- irq = platform_get_irq_byname(pdev, ab8500_fg_irq[i].name);
- ret = request_threaded_irq(irq, NULL, ab8500_fg_irq[i].isr,
- IRQF_SHARED | IRQF_NO_SUSPEND,
- ab8500_fg_irq[i].name, di);
+ /* Register primary interrupt handlers */
+ for (i = 0; i < ARRAY_SIZE(ab8500_fg_irq_th); i++) {
+ irq = platform_get_irq_byname(pdev, ab8500_fg_irq_th[i].name);
+ ret = request_irq(irq, ab8500_fg_irq_th[i].isr,
+ IRQF_SHARED | IRQF_NO_SUSPEND,
+ ab8500_fg_irq_th[i].name, di);

if (ret != 0) {
- dev_err(di->dev, "failed to request %s IRQ %d: %d\n"
- , ab8500_fg_irq[i].name, irq, ret);
+ dev_err(di->dev, "failed to request %s IRQ %d: %d\n",
+ ab8500_fg_irq_th[i].name, irq, ret);
goto free_irq;
}
dev_dbg(di->dev, "Requested %s IRQ %d: %d\n",
- ab8500_fg_irq[i].name, irq, ret);
+ ab8500_fg_irq_th[i].name, irq, ret);
}
+
+ /* Register threaded interrupt handler */
+ irq = platform_get_irq_byname(pdev, ab8500_fg_irq_bh[0].name);
+ ret = request_threaded_irq(irq, NULL, ab8500_fg_irq_bh[0].isr,
+ IRQF_SHARED | IRQF_NO_SUSPEND | IRQF_ONESHOT,
+ ab8500_fg_irq_bh[0].name, di);
+
+ if (ret != 0) {
+ dev_err(di->dev, "failed to request %s IRQ %d: %d\n",
+ ab8500_fg_irq_bh[0].name, irq, ret);
+ goto free_irq;
+ }
+ dev_dbg(di->dev, "Requested %s IRQ %d: %d\n",
+ ab8500_fg_irq_bh[0].name, irq, ret);
+
di->irq = platform_get_irq_byname(pdev, "CCEOC");
disable_irq(di->irq);
di->nbr_cceoc_irq_cnt = 0;
@@ -3245,11 +3263,13 @@ static int ab8500_fg_probe(struct platform_device *pdev)
free_irq:
power_supply_unregister(&di->fg_psy);

- /* We also have to free all successfully registered irqs */
- for (i = i - 1; i >= 0; i--) {
- irq = platform_get_irq_byname(pdev, ab8500_fg_irq[i].name);
+ /* We also have to free all registered irqs */
+ for (i = 0; i < ARRAY_SIZE(ab8500_fg_irq_th); i++) {
+ irq = platform_get_irq_byname(pdev, ab8500_fg_irq_th[i].name);
free_irq(irq, di);
}
+ irq = platform_get_irq_byname(pdev, ab8500_fg_irq_bh[0].name);
+ free_irq(irq, di);
free_inst_curr_wq:
destroy_workqueue(di->fg_wq);
return ret;
--
2.1.0

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