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gpio: do not double-check direction on sleeping chips
When locking a GPIO line as IRQ, we go to lengths to double-check that the line is really set as input before marking it as used for IRQ. This is not good on GPIO chips that can sleep, because this function is called in IRQ-safe context. Just skip this if it can't be checked quickly. Currently this happens on sleeping expanders such as STMPE or TC3589x: BUG: scheduling while atomic: swapper/1/0x00000002 Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 4.9.0-rc1+ #38 Hardware name: Nomadik STn8815 [<c000f2e0>] (unwind_backtrace) from [<c000d244>] (show_stack+0x10/0x14) [<c000d244>] (show_stack) from [<c0037b78>] (__schedule_bug+0x54/0x80) [<c0037b78>] (__schedule_bug) from [<c042df14>] (__schedule+0x3a0/0x460) [<c042df14>] (__schedule) from [<c042e028>] (schedule+0x54/0xb8) (...) This patch fixes that problem and relies on the direction read from the chip when it was added. Cc: [email protected] Fixes: 9c10280 ("gpio: flush direction status in gpiochip_lock_as_irq()") Cc: Patrice Chotard <[email protected]> Signed-off-by: Linus Walleij <[email protected]>
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drivers/gpio/gpiolib.c

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2737,8 +2737,11 @@ int gpiochip_lock_as_irq(struct gpio_chip *chip, unsigned int offset)
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if (IS_ERR(desc))
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return PTR_ERR(desc);
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2740-
/* Flush direction if something changed behind our back */
2741-
if (chip->get_direction) {
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/*
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* If it's fast: flush the direction setting if something changed
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* behind our back
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*/
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if (!chip->can_sleep && chip->get_direction) {
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int dir = chip->get_direction(chip, offset);
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if (dir)

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