| Message ID | 20171013111907.6913-2-hdegoede@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, 2017-10-13 at 13:19 +0200, Hans de Goede wrote: > From: Paul Cercueil <paul@crapouillou.net> > > The Goodix panel triggers an interrupt on touch events. However, its > registers will contain the valid values a short time after the > interrupt, and not when it's raised. At that moment, the 'buffer > status' > bit is set. > > Previously, if the 'buffer status' bit was not set when the registers > were read, the data was discarded and no input event was emitted, > causing "finger down" or "finger up" events to be missed sometimes. > > This went unnoticed until v4.9, as the DesignWare I2C driver commonly > used with this driver had enough latency for that bug to never > trigger. Link to the bug fix? > Now, in the IRQ handler we will poll (with a timeout) the 'buffer > status' > bit and process the data of the panel as soon as this bit gets set. > > Note that the Goodix panel will send a few spurious interrupts after > the > 'finger up' event, in which the 'buffer status' bit will never be > set. > > Cc: Bastien Nocera <hadess@hadess.net> > Cc: russianneuromancer@ya.ru > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > [hdegoede@redhat.com: Change poll loop to use jiffies, > add comment about typical poll time] > Signed-off-by: Hans de Goede <hdegoede@redhat.com> > --- > drivers/input/touchscreen/goodix.c | 36 > ++++++++++++++++++++++++++++-------- > 1 file changed, 28 insertions(+), 8 deletions(-) > > diff --git a/drivers/input/touchscreen/goodix.c > b/drivers/input/touchscreen/goodix.c > index 32d2762448aa..a2071c132a2b 100644 > --- a/drivers/input/touchscreen/goodix.c > +++ b/drivers/input/touchscreen/goodix.c > @@ -195,18 +195,38 @@ static int goodix_get_cfg_len(u16 id) > > static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 > *data) > { > + unsigned long timeout; > int touch_num; > int error; > > - error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, > data, > - GOODIX_CONTACT_SIZE + 1); > - if (error) { > - dev_err(&ts->client->dev, "I2C transfer error: > %d\n", error); > - return error; > - } > + /* > + * The 'buffer status' bit, which indicates that the data is > valid, is > + * not set as soon as the interrupt is raised, but slightly > after. > + * This takes around 10 ms to happen, so we poll for 20 ms. > + */ > + timeout = jiffies + msecs_to_jiffies(20); around 16msec is the time between 2 frames on a 60Hz display. Is 20msec what we want? Does this looping block below any other parts of the kernel, or does it run in its own thread? > + do { > + error = goodix_i2c_read(ts->client, > GOODIX_READ_COOR_ADDR, > + data, GOODIX_CONTACT_SIZE + > 1); > + if (error) { > + dev_err(&ts->client->dev, "I2C transfer > error: %d\n", > + error); > + return error; > + } > > - if (!(data[0] & 0x80)) > - return -EAGAIN; > + if (data[0] & 0x80) > + break; > + > + usleep_range(1000, 2000); /* Poll every 1 - 2 ms */ > + } while (time_before(jiffies, timeout)); > + > + if (!(data[0] & 0x80)) { > + /* > + * The Goodix panel will send spurious interrupts > after a > + * 'finger up' event, which will always cause a > timeout. > + */ > + return 0; > + } > > touch_num = data[0] & 0x0f; > if (touch_num > ts->max_touch_num) -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, On 13-10-17 14:57, Bastien Nocera wrote: > On Fri, 2017-10-13 at 13:19 +0200, Hans de Goede wrote: >> From: Paul Cercueil <paul@crapouillou.net> >> >> The Goodix panel triggers an interrupt on touch events. However, its >> registers will contain the valid values a short time after the >> interrupt, and not when it's raised. At that moment, the 'buffer >> status' >> bit is set. >> >> Previously, if the 'buffer status' bit was not set when the registers >> were read, the data was discarded and no input event was emitted, >> causing "finger down" or "finger up" events to be missed sometimes. >> >> This went unnoticed until v4.9, as the DesignWare I2C driver commonly >> used with this driver had enough latency for that bug to never >> trigger. > > Link to the bug fix? There is this commit seems somewhat related: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/i2c/busses/i2c-designware-core.c?id=2702ea7dbec55db62fa3016c7275fea7b508033f But I think overall it might be best to just remove this paragraph from the commit msg. The problem probably was there all along it just was not noticed until around 4.9. >> Now, in the IRQ handler we will poll (with a timeout) the 'buffer >> status' >> bit and process the data of the panel as soon as this bit gets set. >> >> Note that the Goodix panel will send a few spurious interrupts after >> the >> 'finger up' event, in which the 'buffer status' bit will never be >> set. >> >> Cc: Bastien Nocera <hadess@hadess.net> >> Cc: russianneuromancer@ya.ru >> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> [hdegoede@redhat.com: Change poll loop to use jiffies, >> add comment about typical poll time] >> Signed-off-by: Hans de Goede <hdegoede@redhat.com> >> --- >> drivers/input/touchscreen/goodix.c | 36 >> ++++++++++++++++++++++++++++-------- >> 1 file changed, 28 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/input/touchscreen/goodix.c >> b/drivers/input/touchscreen/goodix.c >> index 32d2762448aa..a2071c132a2b 100644 >> --- a/drivers/input/touchscreen/goodix.c >> +++ b/drivers/input/touchscreen/goodix.c >> @@ -195,18 +195,38 @@ static int goodix_get_cfg_len(u16 id) >> >> static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 >> *data) >> { >> + unsigned long timeout; >> int touch_num; >> int error; >> >> - error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, >> data, >> - GOODIX_CONTACT_SIZE + 1); >> - if (error) { >> - dev_err(&ts->client->dev, "I2C transfer error: >> %d\n", error); >> - return error; >> - } >> + /* >> + * The 'buffer status' bit, which indicates that the data is >> valid, is >> + * not set as soon as the interrupt is raised, but slightly >> after. >> + * This takes around 10 ms to happen, so we poll for 20 ms. >> + */ >> + timeout = jiffies + msecs_to_jiffies(20); > > around 16msec is the time between 2 frames on a 60Hz display. Is 20msec > what we want? It is twice the time which people have observed on touchscreens which need the poll, the idea is that since the normal time is 10ms, we wait somewhat more because of possible jitter in that 10 ms time observed. > Does this looping block below any other parts of the > kernel, or does it run in its own thread? It is only called from goodix_ts_irq_handler which is installed as a threaded interrupt handler, so it runs from its own thread. Other wise we would be unable to do i2c transfers since those can sleep too waiting for the i2c controller to complete the transfer. Regards, Hans > >> + do { >> + error = goodix_i2c_read(ts->client, >> GOODIX_READ_COOR_ADDR, >> + data, GOODIX_CONTACT_SIZE + >> 1); >> + if (error) { >> + dev_err(&ts->client->dev, "I2C transfer >> error: %d\n", >> + error); >> + return error; >> + } >> >> - if (!(data[0] & 0x80)) >> - return -EAGAIN; >> + if (data[0] & 0x80) >> + break; >> + >> + usleep_range(1000, 2000); /* Poll every 1 - 2 ms */ >> + } while (time_before(jiffies, timeout)); >> + >> + if (!(data[0] & 0x80)) { >> + /* >> + * The Goodix panel will send spurious interrupts >> after a >> + * 'finger up' event, which will always cause a >> timeout. >> + */ >> + return 0; >> + } >> >> touch_num = data[0] & 0x0f; >> if (touch_num > ts->max_touch_num) -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2017-10-13 at 15:49 +0200, Hans de Goede wrote: > Hi, > > On 13-10-17 14:57, Bastien Nocera wrote: > > On Fri, 2017-10-13 at 13:19 +0200, Hans de Goede wrote: > > > From: Paul Cercueil <paul@crapouillou.net> > > > > > > The Goodix panel triggers an interrupt on touch events. However, > > > its > > > registers will contain the valid values a short time after the > > > interrupt, and not when it's raised. At that moment, the 'buffer > > > status' > > > bit is set. > > > > > > Previously, if the 'buffer status' bit was not set when the > > > registers > > > were read, the data was discarded and no input event was emitted, > > > causing "finger down" or "finger up" events to be missed > > > sometimes. > > > > > > This went unnoticed until v4.9, as the DesignWare I2C driver > > > commonly > > > used with this driver had enough latency for that bug to never > > > trigger. > > > > Link to the bug fix? > > There is this commit seems somewhat related: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/co > mmit/drivers/i2c/busses/i2c-designware- > core.c?id=2702ea7dbec55db62fa3016c7275fea7b508033f > > But I think overall it might be best to just remove this paragraph > from the commit msg. The problem probably was there all along it > just was not noticed until around 4.9. I'm fine with keeping it along with a reference to the commit. Otherwise it makes it look like the driver was committed broken ;) > > > Now, in the IRQ handler we will poll (with a timeout) the 'buffer > > > status' > > > bit and process the data of the panel as soon as this bit gets > > > set. > > > > > > Note that the Goodix panel will send a few spurious interrupts > > > after > > > the > > > 'finger up' event, in which the 'buffer status' bit will never be > > > set. > > > > > > Cc: Bastien Nocera <hadess@hadess.net> > > > Cc: russianneuromancer@ya.ru > > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > > > [hdegoede@redhat.com: Change poll loop to use jiffies, > > > add comment about typical poll time] > > > Signed-off-by: Hans de Goede <hdegoede@redhat.com> > > > --- > > > drivers/input/touchscreen/goodix.c | 36 > > > ++++++++++++++++++++++++++++-------- > > > 1 file changed, 28 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/input/touchscreen/goodix.c > > > b/drivers/input/touchscreen/goodix.c > > > index 32d2762448aa..a2071c132a2b 100644 > > > --- a/drivers/input/touchscreen/goodix.c > > > +++ b/drivers/input/touchscreen/goodix.c > > > @@ -195,18 +195,38 @@ static int goodix_get_cfg_len(u16 id) > > > > > > static int goodix_ts_read_input_report(struct goodix_ts_data > > > *ts, u8 > > > *data) > > > { > > > + unsigned long timeout; > > > int touch_num; > > > int error; > > > > > > - error = goodix_i2c_read(ts->client, > > > GOODIX_READ_COOR_ADDR, > > > data, > > > - GOODIX_CONTACT_SIZE + 1); > > > - if (error) { > > > - dev_err(&ts->client->dev, "I2C transfer error: > > > %d\n", error); > > > - return error; > > > - } > > > + /* > > > + * The 'buffer status' bit, which indicates that the > > > data is > > > valid, is > > > + * not set as soon as the interrupt is raised, but > > > slightly > > > after. > > > + * This takes around 10 ms to happen, so we poll for 20 > > > ms. > > > + */ > > > + timeout = jiffies + msecs_to_jiffies(20); > > > > around 16msec is the time between 2 frames on a 60Hz display. Is > > 20msec > > what we want? > > It is twice the time which people have observed on touchscreens > which need the poll, the idea is that since the normal time is > 10ms, we wait somewhat more because of possible jitter in that > 10 ms time observed. Ha, so 20msec in 1-2msec increments sounds fine. Could you rename that to "max_timeout", and make "20" a constant? > > Does this looping block below any other parts of the > > kernel, or does it run in its own thread? > > It is only called from goodix_ts_irq_handler which is > installed as a threaded interrupt handler, so it runs > from its own thread. Other wise we would be unable to do > i2c transfers since those can sleep too waiting for the > i2c controller to complete the transfer. Looks good otherwise. Thanks for looking into this! -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/input/touchscreen/goodix.c b/drivers/input/touchscreen/goodix.c index 32d2762448aa..a2071c132a2b 100644 --- a/drivers/input/touchscreen/goodix.c +++ b/drivers/input/touchscreen/goodix.c @@ -195,18 +195,38 @@ static int goodix_get_cfg_len(u16 id) static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 *data) { + unsigned long timeout; int touch_num; int error; - error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, data, - GOODIX_CONTACT_SIZE + 1); - if (error) { - dev_err(&ts->client->dev, "I2C transfer error: %d\n", error); - return error; - } + /* + * The 'buffer status' bit, which indicates that the data is valid, is + * not set as soon as the interrupt is raised, but slightly after. + * This takes around 10 ms to happen, so we poll for 20 ms. + */ + timeout = jiffies + msecs_to_jiffies(20); + do { + error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, + data, GOODIX_CONTACT_SIZE + 1); + if (error) { + dev_err(&ts->client->dev, "I2C transfer error: %d\n", + error); + return error; + } - if (!(data[0] & 0x80)) - return -EAGAIN; + if (data[0] & 0x80) + break; + + usleep_range(1000, 2000); /* Poll every 1 - 2 ms */ + } while (time_before(jiffies, timeout)); + + if (!(data[0] & 0x80)) { + /* + * The Goodix panel will send spurious interrupts after a + * 'finger up' event, which will always cause a timeout. + */ + return 0; + } touch_num = data[0] & 0x0f; if (touch_num > ts->max_touch_num)