The downstream driver sets the regulator voltage to 3.1 V. Without this,
the touchscreen generates random touches even after it is no longer
being touched. It is unknown whether the same problem appears with other
chips of the IST30**C series.
Co-developed-by: Duje Mihanović <[email protected]>
Signed-off-by: Duje Mihanović <[email protected]>
Signed-off-by: Karel Balej <[email protected]>
---
.../bindings/input/touchscreen/imagis,ist30xxc.yaml | 1 +
drivers/input/touchscreen/imagis.c | 13 +++++++++++++
2 files changed, 14 insertions(+)
diff --git a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
index 09bf3a6acc5e..d6f75bbfaec3 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
+++ b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
@@ -18,6 +18,7 @@ properties:
compatible:
enum:
+ - imagis,ist3032c
- imagis,ist3038c
reg:
diff --git a/drivers/input/touchscreen/imagis.c b/drivers/input/touchscreen/imagis.c
index 4456f1b4d527..df9a8fbf2c5f 100644
--- a/drivers/input/touchscreen/imagis.c
+++ b/drivers/input/touchscreen/imagis.c
@@ -30,6 +30,7 @@
#define IST30XXC_FINGER_COUNT_SHIFT 12
#define IST30XXC_FINGER_STATUS_MASK GENMASK(9, 0)
+#define IST3032C_WHOAMI 0x32c
#define IST3038C_WHOAMI 0x38c
struct imagis_ts {
@@ -295,6 +296,16 @@ static int imagis_probe(struct i2c_client *i2c)
return -EINVAL;
}
+ if (chip_id == IST3032C_WHOAMI) {
+ /*
+ * if the regulator voltage is not set like this, the touchscreen
+ * generates random touches without user interaction
+ */
+ error = regulator_set_voltage(ts->supplies[0].consumer, 3100000, 3100000);
+ if (error)
+ dev_warn(dev, "failed to set regulator voltage\n");
+ }
+
error = devm_request_threaded_irq(dev, i2c->irq,
NULL, imagis_interrupt,
IRQF_ONESHOT | IRQF_NO_AUTOEN,
@@ -348,6 +359,7 @@ static DEFINE_SIMPLE_DEV_PM_OPS(imagis_pm_ops, imagis_suspend, imagis_resume);
#ifdef CONFIG_OF
static const struct of_device_id imagis_of_match[] = {
+ { .compatible = "imagis,ist3032c", .data = (void *)IST3032C_WHOAMI, },
{ .compatible = "imagis,ist3038c", .data = (void *)IST3038C_WHOAMI, },
{ },
};
@@ -355,6 +367,7 @@ MODULE_DEVICE_TABLE(of, imagis_of_match);
#endif
static const struct i2c_device_id imagis_ts_i2c_id[] = {
+ { "ist3032c", IST3032C_WHOAMI, },
{ "ist3038c", IST3038C_WHOAMI, },
{ },
};
--
2.42.0
Hi Karel,
On Tue, Sep 26, 2023 at 07:35:24PM +0200, Karel Balej wrote:
> The downstream driver sets the regulator voltage to 3.1 V. Without this,
> the touchscreen generates random touches even after it is no longer
> being touched. It is unknown whether the same problem appears with other
> chips of the IST30**C series.
>
> Co-developed-by: Duje Mihanović <[email protected]>
> Signed-off-by: Duje Mihanović <[email protected]>
> Signed-off-by: Karel Balej <[email protected]>
> ---
> .../bindings/input/touchscreen/imagis,ist30xxc.yaml | 1 +
> drivers/input/touchscreen/imagis.c | 13 +++++++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
> index 09bf3a6acc5e..d6f75bbfaec3 100644
> --- a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
> +++ b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist30xxc.yaml
> @@ -18,6 +18,7 @@ properties:
>
> compatible:
> enum:
> + - imagis,ist3032c
> - imagis,ist3038c
>
> reg:
> diff --git a/drivers/input/touchscreen/imagis.c b/drivers/input/touchscreen/imagis.c
> index 4456f1b4d527..df9a8fbf2c5f 100644
> --- a/drivers/input/touchscreen/imagis.c
> +++ b/drivers/input/touchscreen/imagis.c
> @@ -30,6 +30,7 @@
> #define IST30XXC_FINGER_COUNT_SHIFT 12
> #define IST30XXC_FINGER_STATUS_MASK GENMASK(9, 0)
>
> +#define IST3032C_WHOAMI 0x32c
> #define IST3038C_WHOAMI 0x38c
>
> struct imagis_ts {
> @@ -295,6 +296,16 @@ static int imagis_probe(struct i2c_client *i2c)
> return -EINVAL;
> }
>
> + if (chip_id == IST3032C_WHOAMI) {
> + /*
> + * if the regulator voltage is not set like this, the touchscreen
> + * generates random touches without user interaction
> + */
> + error = regulator_set_voltage(ts->supplies[0].consumer, 3100000, 3100000);
> + if (error)
> + dev_warn(dev, "failed to set regulator voltage\n");
> + }
> +
Opinions may vary, but mine is that this kind of hard-coded board-level policy
does not belong in the driver. Surely the supply need not be equal to exactly
3.1 V and this is merely an upper or lower limit? Assuming so, what if the board
designer opts to share this supply with another consumer that requires a specific
voltage not equal to 3.1 V, but still within the safe range of IST3032C?
To me, this restriction belongs in dts, specifically within the regulator child
node referenced by the client which bears the new 'ist3032c' compatible string.
Maybe a better solution is to simply note this presumed silicon erratum in the
description of the vdd supply in the binding which, as Conor states, must not be
clubbed with driver patches.
> error = devm_request_threaded_irq(dev, i2c->irq,
> NULL, imagis_interrupt,
> IRQF_ONESHOT | IRQF_NO_AUTOEN,
> @@ -348,6 +359,7 @@ static DEFINE_SIMPLE_DEV_PM_OPS(imagis_pm_ops, imagis_suspend, imagis_resume);
>
> #ifdef CONFIG_OF
> static const struct of_device_id imagis_of_match[] = {
> + { .compatible = "imagis,ist3032c", .data = (void *)IST3032C_WHOAMI, },
> { .compatible = "imagis,ist3038c", .data = (void *)IST3038C_WHOAMI, },
> { },
> };
> @@ -355,6 +367,7 @@ MODULE_DEVICE_TABLE(of, imagis_of_match);
> #endif
>
> static const struct i2c_device_id imagis_ts_i2c_id[] = {
> + { "ist3032c", IST3032C_WHOAMI, },
> { "ist3038c", IST3038C_WHOAMI, },
> { },
> };
> --
> 2.42.0
>
Kind regards,
Jeff LaBundy
On 26/09/2023 19:35, Karel Balej wrote:
> The downstream driver sets the regulator voltage to 3.1 V. Without this,
> the touchscreen generates random touches even after it is no longer
> being touched. It is unknown whether the same problem appears with other
> chips of the IST30**C series.
>
> Co-developed-by: Duje Mihanović <[email protected]>
> Signed-off-by: Duje Mihanović <[email protected]>
> Signed-off-by: Karel Balej <[email protected]>
> ---
> .../bindings/input/touchscreen/imagis,ist30xxc.yaml | 1 +
Bindings are always separate patches. Always.
Please run scripts/checkpatch.pl and fix reported warnings. Some
warnings can be ignored, but the code here looks like it needs a fix.
Feel free to get in touch if the warning is not clear.
Please use subject prefixes matching the subsystem. You can get them for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching.
Best regards,
Krzysztof
Hello, Jeff,
thank you very much for your feedback.
> > + if (chip_id == IST3032C_WHOAMI) {
> > + /*
> > + * if the regulator voltage is not set like this, the touchscreen
> > + * generates random touches without user interaction
> > + */
> > + error = regulator_set_voltage(ts->supplies[0].consumer, 3100000, 3100000);
> > + if (error)
> > + dev_warn(dev, "failed to set regulator voltage\n");
> > + }
> > +
>
> Opinions may vary, but mine is that this kind of hard-coded board-level policy
> does not belong in the driver. Surely the supply need not be equal to exactly
> 3.1 V and this is merely an upper or lower limit? Assuming so, what if the board
> designer opts to share this supply with another consumer that requires a specific
> voltage not equal to 3.1 V, but still within the safe range of IST3032C?
>
> To me, this restriction belongs in dts, specifically within the regulator child
> node referenced by the client which bears the new 'ist3032c' compatible string.
> Maybe a better solution is to simply note this presumed silicon erratum in the
> description of the vdd supply in the binding which, as Conor states, must not be
> clubbed with driver patches.
I agree that the voltage should not be hardcoded. I do not know what the
safe range for the touchscreen is though, because the downstream driver
does exactly this. I will try to test it with several values within the
range allowed by the regulator and see if I can determine some limits on
when the "ghost" touches do not appear.
However I am not sure whether this setting should be moved to the
regulator DT - it is my understanding that the DT for the regulator
should list the min/max range *supported* by the regulator, not conform
to requirements of its consumers, which should instead ask for the
regulator to be set to a range they require themselves, via their driver
- is it not so?
The regulator driver is not mainlined yet (although I managed to get the
downstream code working with mainline), however the downstream DT
contains much wider range of supported voltage (compared to those 3.1 V
used by the touchscreen) - an information which would get lost if I set
the DT for the regulator by the requirements of the touchscreen, which I
believe would have similiar implications as what you said regarding
using this regulator with other consumers.
What would seem a reasonable solution to me would be to move the voltage
range values to the touchscreen DT (which incidentally is what the
downstream driver does also, except it uses one value for both min and
max), so that they would be set by the driver but not hardcoded in the
code - what do you think about this?
Best regards,
K. B.
Hi Karel,
On Thu, Sep 28, 2023 at 07:56:45PM +0200, Karel Balej wrote:
> Hello, Jeff,
>
> thank you very much for your feedback.
>
> > > + if (chip_id == IST3032C_WHOAMI) {
> > > + /*
> > > + * if the regulator voltage is not set like this, the touchscreen
> > > + * generates random touches without user interaction
> > > + */
> > > + error = regulator_set_voltage(ts->supplies[0].consumer, 3100000, 3100000);
> > > + if (error)
> > > + dev_warn(dev, "failed to set regulator voltage\n");
> > > + }
> > > +
> >
> > Opinions may vary, but mine is that this kind of hard-coded board-level policy
> > does not belong in the driver. Surely the supply need not be equal to exactly
> > 3.1 V and this is merely an upper or lower limit? Assuming so, what if the board
> > designer opts to share this supply with another consumer that requires a specific
> > voltage not equal to 3.1 V, but still within the safe range of IST3032C?
> >
> > To me, this restriction belongs in dts, specifically within the regulator child
> > node referenced by the client which bears the new 'ist3032c' compatible string.
> > Maybe a better solution is to simply note this presumed silicon erratum in the
> > description of the vdd supply in the binding which, as Conor states, must not be
> > clubbed with driver patches.
>
> I agree that the voltage should not be hardcoded. I do not know what the
> safe range for the touchscreen is though, because the downstream driver
> does exactly this. I will try to test it with several values within the
> range allowed by the regulator and see if I can determine some limits on
> when the "ghost" touches do not appear.
>
> However I am not sure whether this setting should be moved to the
> regulator DT - it is my understanding that the DT for the regulator
> should list the min/max range *supported* by the regulator, not conform
> to requirements of its consumers, which should instead ask for the
> regulator to be set to a range they require themselves, via their driver
> - is it not so?
>
> The regulator driver is not mainlined yet (although I managed to get the
> downstream code working with mainline), however the downstream DT
> contains much wider range of supported voltage (compared to those 3.1 V
> used by the touchscreen) - an information which would get lost if I set
> the DT for the regulator by the requirements of the touchscreen, which I
> believe would have similiar implications as what you said regarding
> using this regulator with other consumers.
>
> What would seem a reasonable solution to me would be to move the voltage
> range values to the touchscreen DT (which incidentally is what the
> downstream driver does also, except it uses one value for both min and
> max), so that they would be set by the driver but not hardcoded in the
> code - what do you think about this?
I believe this has been clarified in the other thread with Markuss, but
just to close this out: in general, individual drivers should not be
setting the output value of a regulator. Instead, they should merely mark
themselves as a consumer of a regulator, and increment or decrement its
usage counter by enabling and disabling the regulator, respectively.
You are correct that the regulator node typically specifies the minimum
and maximum voltages supported by the regulator, but if your board has
a stricter range because said regulator is tied to something such as this
touchscreen controller, then you can override the maximum voltage with
something smaller (e.g. 3.1 V). The regulator framework will then set the
output voltage according to the ultimate range defined in the device tree.
Often times the baseline regulator nodes are defined in a PMIC-specific
.dtsi file, or part of a more generic board definition. Then, some nodes
are overridden at a higher level in the heirarchy tailored to the board,
or an overlay applied by the bootloader.
>
> Best regards,
> K. B.
Kind regards,
Jeff LaBundy