On Dec 18 2015 or thereabouts, Mika Westerberg wrote:
> On Fri, Dec 18, 2015 at 04:42:09PM +0200, Mika Westerberg wrote:
> > On another occasion the faulty input report was received immediatelly
> > after we call i2c_hid_set_power().
> >
> > With below hack patch suspend/resume works fine but it is far from being
> > suitable for merging. Still, it would be nice if you could try it out
> > and see if it helps in your case.
>
> Actually it looks like we can handle this by just ignoring input reports
> while we are resetting the device. Following seems to work as well.
Yes, I like this one better. I think, it is still prone to races, but
it's a much better option.
After turning this around, I think I finally got what was going on (and
yes, it's basically a race that should have been caught long ago):
- during resume, the i2c-hid driver calls reset, which is a long (few
ms) operation.
- hid-multitouch is also called during resume, and right after i2c-hid
- hid-multiotuch immediately emits for touchpads a set input mode (this
was unseen with touchscreens because they do not have to be switched
into a proper mode)
- there is a race between hid-multitouch accessing the features while
the device is still resetting. And our reset interrupt never gets to
us because there was an other operation in progress to request/set
reports
So the actual fix would be to make hid-multitouch wait until we reset
i2c-hid.
This should be done by either a mutex or a spinlock in
i2c_hid_output_raw_report() and i2c_hid_resume() that would protect a
flag set during suspend and cleared after resume.
(not sure if this is clear :-P )
Cheers,
Benjamin
>
> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> index 10bd8e6..eeaf33a 100644
> --- a/drivers/hid/i2c-hid/i2c-hid.c
> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> @@ -352,13 +352,24 @@ static int i2c_hid_set_power(struct i2c_client *client,
> int power_state)
> static int i2c_hid_hwreset(struct i2c_client *client)
> {
> struct i2c_hid *ihid = i2c_get_clientdata(client);
> + bool started;
> int ret;
>
> i2c_hid_dbg(ihid, "%s\n", __func__);
>
> + /*
> + * Some touchpads seem to send input reports once their power is
> + * turned back on after resume. This confuses our reset logic
> + * below.
> + *
> + * Prevent handling any input reports while we are resetting the
> + * device.
> + */
> + started = test_and_clear_bit(I2C_HID_STARTED, &ihid->flags);
> +
> ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
> if (ret)
> - return ret;
> + goto out;
>
> i2c_hid_dbg(ihid, "resetting...\n");
>
> @@ -366,10 +377,14 @@ static int i2c_hid_hwreset(struct i2c_client *client)
> if (ret) {
> dev_err(&client->dev, "failed to reset device.\n");
> i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
> - return ret;
> + goto out;
> }
>
> - return 0;
> +out:
> + if (started)
> + set_bit(I2C_HID_STARTED, &ihid->flags);
> +
> + return ret;
> }
>
> static void i2c_hid_get_input(struct i2c_hid *ihid)
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