| Message ID | 20211108005216.480525-1-marex@denx.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 8639e042ad6aca7fc2a5b2fe8652396e2f522627 |
| Headers | show |
| Series | Input: ili210x - Improve polled sample spacing | expand |
Hi Marek, On Mon, Nov 08, 2021 at 01:52:16AM +0100, Marek Vasut wrote: > Currently the ili210x driver implements a threaded interrupt handler which > starts upon edge on the interrupt line, and then polls the touch controller > for samples. Every time a sample is obtained from the controller, the thread > function checks whether further polling is required, and if so, waits fixed > amount of time before polling for next sample. > > The delay between consecutive samples can thus vary greatly, because the > I2C transfer required to retrieve the sample from the controller takes > different amount of time on different platforms. Furthermore, different > models of the touch controllers supported by this driver require different > delays during retrieval of samples too. > > Instead of waiting fixed amount of time before polling for next sample, > determine how much time passed since the beginning of sampling cycle and > then wait only the remaining amount of time within the sampling cycle. > This makes the driver deliver samples with equal spacing between them. > > Signed-off-by: Marek Vasut <marex@denx.de> > Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> > Cc: Joe Hung <joe_hung@ilitek.com> > Cc: Luca Hsu <luca_hsu@ilitek.com> > --- > drivers/input/touchscreen/ili210x.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/input/touchscreen/ili210x.c b/drivers/input/touchscreen/ili210x.c > index a3b71a9511eb3..b2d9fe1e1c707 100644 > --- a/drivers/input/touchscreen/ili210x.c > +++ b/drivers/input/touchscreen/ili210x.c > @@ -328,10 +328,13 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) > const struct ili2xxx_chip *chip = priv->chip; > u8 touchdata[ILI210X_DATA_SIZE] = { 0 }; > bool keep_polling; > + ktime_t time_next; > + s64 time_delta; > bool touch; > int error; > > do { > + time_next = ktime_add_ms(ktime_get(), ILI2XXX_POLL_PERIOD); > error = chip->get_touch_data(client, touchdata); > if (error) { > dev_err(&client->dev, > @@ -341,8 +344,11 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) > > touch = ili210x_report_events(priv, touchdata); > keep_polling = chip->continue_polling(touchdata, touch); > - if (keep_polling) > - msleep(ILI2XXX_POLL_PERIOD); > + if (keep_polling) { > + time_delta = ktime_us_delta(time_next, ktime_get()); Do we really need to use exact time, or ktime_get_coarse() is good enough, as it is cheaper? > + if (time_delta > 0) > + usleep_range(time_delta, time_delta + 1000); > + } > } while (!priv->stop && keep_polling); > > return IRQ_HANDLED; > -- > 2.33.0 > Thanks.
On 11/8/21 4:37 AM, Dmitry Torokhov wrote: > Hi Marek, Hi, [...] >> diff --git a/drivers/input/touchscreen/ili210x.c b/drivers/input/touchscreen/ili210x.c >> index a3b71a9511eb3..b2d9fe1e1c707 100644 >> --- a/drivers/input/touchscreen/ili210x.c >> +++ b/drivers/input/touchscreen/ili210x.c >> @@ -328,10 +328,13 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) >> const struct ili2xxx_chip *chip = priv->chip; >> u8 touchdata[ILI210X_DATA_SIZE] = { 0 }; >> bool keep_polling; >> + ktime_t time_next; >> + s64 time_delta; >> bool touch; >> int error; >> >> do { >> + time_next = ktime_add_ms(ktime_get(), ILI2XXX_POLL_PERIOD); >> error = chip->get_touch_data(client, touchdata); >> if (error) { >> dev_err(&client->dev, >> @@ -341,8 +344,11 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) >> >> touch = ili210x_report_events(priv, touchdata); >> keep_polling = chip->continue_polling(touchdata, touch); >> - if (keep_polling) >> - msleep(ILI2XXX_POLL_PERIOD); >> + if (keep_polling) { >> + time_delta = ktime_us_delta(time_next, ktime_get()); > > Do we really need to use exact time, or ktime_get_coarse() is good > enough, as it is cheaper? ktime_get_coarse() introduces multi-millisecond jitter into the samples if you have low HZ setting, which isn't really nice. That's also why I use ktime and not jiffies here, jiffies has the same problem.
On Mon, Nov 08, 2021 at 12:04:30PM +0100, Marek Vasut wrote: > On 11/8/21 4:37 AM, Dmitry Torokhov wrote: > > Hi Marek, > > Hi, > > [...] > > > > diff --git a/drivers/input/touchscreen/ili210x.c b/drivers/input/touchscreen/ili210x.c > > > index a3b71a9511eb3..b2d9fe1e1c707 100644 > > > --- a/drivers/input/touchscreen/ili210x.c > > > +++ b/drivers/input/touchscreen/ili210x.c > > > @@ -328,10 +328,13 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) > > > const struct ili2xxx_chip *chip = priv->chip; > > > u8 touchdata[ILI210X_DATA_SIZE] = { 0 }; > > > bool keep_polling; > > > + ktime_t time_next; > > > + s64 time_delta; > > > bool touch; > > > int error; > > > do { > > > + time_next = ktime_add_ms(ktime_get(), ILI2XXX_POLL_PERIOD); > > > error = chip->get_touch_data(client, touchdata); > > > if (error) { > > > dev_err(&client->dev, > > > @@ -341,8 +344,11 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) > > > touch = ili210x_report_events(priv, touchdata); > > > keep_polling = chip->continue_polling(touchdata, touch); > > > - if (keep_polling) > > > - msleep(ILI2XXX_POLL_PERIOD); > > > + if (keep_polling) { > > > + time_delta = ktime_us_delta(time_next, ktime_get()); > > > > Do we really need to use exact time, or ktime_get_coarse() is good > > enough, as it is cheaper? > > ktime_get_coarse() introduces multi-millisecond jitter into the samples if > you have low HZ setting, which isn't really nice. That's also why I use > ktime and not jiffies here, jiffies has the same problem. Applied, thank you.
diff --git a/drivers/input/touchscreen/ili210x.c b/drivers/input/touchscreen/ili210x.c index a3b71a9511eb3..b2d9fe1e1c707 100644 --- a/drivers/input/touchscreen/ili210x.c +++ b/drivers/input/touchscreen/ili210x.c @@ -328,10 +328,13 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) const struct ili2xxx_chip *chip = priv->chip; u8 touchdata[ILI210X_DATA_SIZE] = { 0 }; bool keep_polling; + ktime_t time_next; + s64 time_delta; bool touch; int error; do { + time_next = ktime_add_ms(ktime_get(), ILI2XXX_POLL_PERIOD); error = chip->get_touch_data(client, touchdata); if (error) { dev_err(&client->dev, @@ -341,8 +344,11 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data) touch = ili210x_report_events(priv, touchdata); keep_polling = chip->continue_polling(touchdata, touch); - if (keep_polling) - msleep(ILI2XXX_POLL_PERIOD); + if (keep_polling) { + time_delta = ktime_us_delta(time_next, ktime_get()); + if (time_delta > 0) + usleep_range(time_delta, time_delta + 1000); + } } while (!priv->stop && keep_polling); return IRQ_HANDLED;
Currently the ili210x driver implements a threaded interrupt handler which starts upon edge on the interrupt line, and then polls the touch controller for samples. Every time a sample is obtained from the controller, the thread function checks whether further polling is required, and if so, waits fixed amount of time before polling for next sample. The delay between consecutive samples can thus vary greatly, because the I2C transfer required to retrieve the sample from the controller takes different amount of time on different platforms. Furthermore, different models of the touch controllers supported by this driver require different delays during retrieval of samples too. Instead of waiting fixed amount of time before polling for next sample, determine how much time passed since the beginning of sampling cycle and then wait only the remaining amount of time within the sampling cycle. This makes the driver deliver samples with equal spacing between them. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Cc: Joe Hung <joe_hung@ilitek.com> Cc: Luca Hsu <luca_hsu@ilitek.com> --- drivers/input/touchscreen/ili210x.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)