Am 21.02.2017 um 16:07 schrieb Michael Zoran:
On Mon, 2017-02-20 at 22:22 +0100, Noralf Trønnes wrote:
Den 20.02.2017 20.40, skrev Stefan Wahren:
Hi,
Noralf Trønnes <noralf@xxxxxxxxxxx> hat am 18. Februar 2017 um
19:34 geschrieben:
Den 16.02.2017 22.20, skrev Stefan Wahren:
Since commit e2474541032d ("bcm2835: Fix hang for writing
messages
larger than 16 bytes") the interrupt handler is prone to a
possible
NULL pointer dereference. This could happen if an interrupt
fires
before curr_msg is set by bcm2835_i2c_xfer_msg() and randomly
occurs
on the RPi 3. Even this is an unexpected behavior the driver
must
handle that with an error instead of a crash.
CC: Noralf Trønnes <noralf@xxxxxxxxxxx>
CC: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
Reported-by: Peter Robinson <pbrobinson@xxxxxxxxx>
Fixes: e2474541032d ("bcm2835: Fix hang for writing messages
larger than 16 bytes")
Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
---
drivers/i2c/busses/i2c-bcm2835.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/busses/i2c-bcm2835.c
b/drivers/i2c/busses/i2c-bcm2835.c
index c3436f6..10e39c8 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -195,7 +195,9 @@ static irqreturn_t bcm2835_i2c_isr(int
this_irq, void *data)
}
if (val & BCM2835_I2C_S_DONE) {
- if (i2c_dev->curr_msg->flags & I2C_M_RD) {
+ if (!i2c_dev->curr_msg) {
+ dev_err(i2c_dev->dev, "Got unexpected
interrupt (from firmware?)\n");
+ } else if (i2c_dev->curr_msg->flags &
I2C_M_RD) {
bcm2835_drain_rxfifo(i2c_dev);
val = bcm2835_i2c_readl(i2c_dev,
BCM2835_I2C_S);
}
Thanks,
Acked-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
thanks, but i would be more happier to receive feedback for patches
2 and 3.
I have only worked on dts files downstream and never done any arm64
stuff, so I'm not up to speed on this.
Noralf.
Just a note, the original downstream driver returns IRQ_NONE in this
case. Does that make any difference?
Yes, i decided to handle the IRQ in order to avoid a possible interrupt
storm. Please look at the github discussion [1] for more details.
Also, the the original driver has the check at the start of the IRQ and
it doesn't log an error message.
I'm wondering if logging at err level is the best since it might make
people think a serious error has happened.
It is a serious error and should be fixed by patch 2, 3 and a possible
patch 4 later to disable i2c0.
But before i disable i2c0 we need the test results of patch 2 and 3. The
reason why i don't disable i2c at first is that Gerd [2] reported that
disabling the PWM fixed the i2c timeout issue, which doesn't fit to
Martins theory.
[1] - https://github.com/anholt/linux/issues/89
[2] -
http://lists.infradead.org/pipermail/linux-rpi-kernel/2016-June/003969.html
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