pinctrl: mcp23s08: fix race condition in irq handler

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Checking value of MCP_INTF in mcp23s08_irq suggests that the handler may be
called even when there is no interrupt pending.

But the actual interrupt could happened between reading MCP_INTF and MCP_GPIO.
In this situation we got nothing from MCP_INTF, but the event gets acknowledged
on the expander by reading MCP_GPIO. This leads to losing events.

Fix the problem by not reading any register until we see something in MCP_INTF.

The error was reproduced and fix tested on MCP23017.

Signed-off-by: Radim Pavlik <radim.pavlik@tbs-biometrics.com>
Link: https://lore.kernel.org/r/AM7PR06MB6769E1183F68DEBB252F665ABA3E9@AM7PR06MB6769.eurprd06.prod.outlook.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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Radim Pavlik 2021-06-01 10:48:18 +00:00 • committed by Linus Walleij

parent 50bdc4d441

commit 897120d41e

1 changed files with 5 additions and 5 deletions

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drivers/pinctrl/pinctrl-mcp23s08.c

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