lkml.org 
[lkml]   [2021]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH AUTOSEL 5.4 28/74] pinctrl: mcp23s08: fix race condition in irq handler
Date
From: Radim Pavlik <radim.pavlik@tbs-biometrics.com>

[ Upstream commit 897120d41e7afd9da435cb00041a142aeeb53c07 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pinctrl/pinctrl-mcp23s08.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index d8bcbefcba89..9d5e2d9b6b93 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -459,6 +459,11 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
if (mcp_read(mcp, MCP_INTF, &intf))
goto unlock;

+ if (intf == 0) {
+ /* There is no interrupt pending */
+ return IRQ_HANDLED;
+ }
+
if (mcp_read(mcp, MCP_INTCAP, &intcap))
goto unlock;

@@ -476,11 +481,6 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
mcp->cached_gpio = gpio;
mutex_unlock(&mcp->lock);

- if (intf == 0) {
- /* There is no interrupt pending */
- return IRQ_HANDLED;
- }
-
dev_dbg(mcp->chip.parent,
"intcap 0x%04X intf 0x%04X gpio_orig 0x%04X gpio 0x%04X\n",
intcap, intf, gpio_orig, gpio);
--
2.30.2
\
 
 \ /
  Last update: 2021-07-06 14:10    [W:0.194 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site