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button: adc: set state to pressed when the voltage is closest to nominal

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In the Linux implementation of adc-keys
(drivers/input/keyboard/adc-keys.c), `press-threshold-microvolt` is not
really interpreted as a threshold, but rather as the "nominal voltage"
of the button. When the voltage read from the ADC is closest to a
button's `press-threshold-microvolt`, the button is considered pressed.

This patch reconciles the behavior of button-adc with Linux's adc-keys
such that device trees can be synchronized with minimal modifications.

Signed-off-by: Peter Cai <peter@typeblog.net>
This commit is contained in:
Peter Cai 2022-02-02 13:04:04 -05:00 committed by Tom Rini
parent 0290146943
commit 80d4c02b93
1 changed files with 16 additions and 5 deletions
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21
drivers/button/button-adc.c
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@ -55,7 +55,7 @@ static int button_adc_of_to_plat(struct udevice *dev)
struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev); struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev);
struct button_adc_priv *priv = dev_get_priv(dev); struct button_adc_priv *priv = dev_get_priv(dev);
struct ofnode_phandle_args args; struct ofnode_phandle_args args;
u32 threshold, up_threshold, t; u32 down_threshold = 0, up_threshold, voltage, t;
ofnode node; ofnode node;
int ret; int ret;
@ -78,7 +78,7 @@ static int button_adc_of_to_plat(struct udevice *dev)
return ret; return ret;
ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt", ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt",
&threshold); &voltage);
if (ret) if (ret)
return ret; return ret;
@ -87,13 +87,24 @@ static int button_adc_of_to_plat(struct udevice *dev)
if (ret) if (ret)
return ret; return ret;
if (t > threshold) if (t > voltage && t < up_threshold)
up_threshold = t; up_threshold = t;
else if (t < voltage && t > down_threshold)
down_threshold = t;
} }
priv->channel = args.args[0]; priv->channel = args.args[0];
priv->min = threshold;
priv->max = up_threshold; /*
* Define the voltage range such that the button is only pressed
* when the voltage is closest to its own press-threshold-microvolt
*/
if (down_threshold == 0)
priv->min = 0;
else
priv->min = down_threshold + (voltage - down_threshold) / 2;
priv->max = voltage + (up_threshold - voltage) / 2;
return ret; return ret;
} }