Hi Felipe,
Initially you made the change (66b9298878742f08cb6e79b7c7d5632d782fd1e1):
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/i2c/busses/i2c-omap.c?id=66b9298878742f08cb6e79b7c7d5632d782fd1e1
dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);
if (count++ == 100) {
dev_warn(dev->dev, "Too much work in one IRQ\n");
- break;
+ omap_i2c_complete_cmd(dev, err);
+ return IRQ_HANDLED;
}
Than that change transformed into (4a7ec4eda58269a507501f240955d99312fdfd5f):
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/i2c/busses/i2c-omap.c?id=4a7ec4eda58269a507501f240955d99312fdfd5f
@@ -853,24 +853,21 @@ omap_i2c_isr(int this_irq, void *dev_id)
dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);
if (count++ == 100) {
dev_warn(dev->dev, "Too much work in one IRQ\n");
- omap_i2c_complete_cmd(dev, err);
- return IRQ_HANDLED;
+ goto out;
}
+out:
+ omap_i2c_complete_cmd(dev, err);
return IRQ_HANDLED;
}
As a result we have in master:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/i2c/busses/i2c-omap.c
do {
bits = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
stat = omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG);
stat &= bits;
...
dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);
if (count++ == 100) {
dev_warn(dev->dev, "Too much work in one IRQ\n");
break;
}
...
} while (stat);
omap_i2c_complete_cmd(dev, err);
out:
spin_unlock_irqrestore(&dev->lock, flags);
While original code was:
{
bits = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
while ((stat = (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG))) & bits) {
dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);
if (count++ == 100) {
dev_warn(dev->dev, "Too much work in one IRQ\n");
break;
}
err = 0;
complete:
...
if (stat & (OMAP_I2C_STAT_ARDY | OMAP_I2C_STAT_NACK |
OMAP_I2C_STAT_AL)) {
...
omap_i2c_complete_cmd(dev, err);
return IRQ_HANDLED;
}
...
}
return count ? IRQ_HANDLED : IRQ_NONE;
}
> how ? This is an interesting bug which deserves further explanation.
Look at the loops above, and at the omap_i2c_complete_cmd:
static inline void
omap_i2c_complete_cmd(struct omap_i2c_dev *dev, u16 err)
{
dev->cmd_err |= err;
complete(&dev->cmd_complete);
}
You can see, loop will be aborted if counter reached 100. Final state of
transfer depends on
values stored in the 'err' and 'dev->cmd_err'. If 'err' and 'dev->cmd_err' are
zero, than transfer
would be aborted with status 0.
> quite frankly, this looks *very* wrong. It creates the possibility for
> us never completing a command which would cause several timeouts.
Pre 66b9298878742f08cb6e79b7c7d5632d782fd1e1 omap-i2c.c version didn't cause
deadlocks.
>
> How have you tested this and how have you figured this was the actual
> bug ? Based on commit log not matching the patch body (which 'original
> logic' are you talking about ?), I have to NAK this patch.
Well, I tried to debug I2C ISR hang issue (thats another question I want to
discuss later)
using output to console. I places few dev_warn (not dev_dbg) messages into ISR
(like got NACK, got ARDY and so on) and got "Too much work in one IRQ" with
incorrect booting.
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