[Linux-stm32] [PATCH v1 2/7] ARM: dts: stm32: stm32mp15x-mecio1-io: Fix ADC sampling times

[Oleksij Rempel]

From: David Jander <david at protonic.nl>

Increase the minimum ADC sample times for all configured channels on
ADC1 and ADC2 to ensure measurement accuracy meets specifications.

The default 5us sample time is insufficient for the internal sampling
capacitor to fully charge. Increase the default time to 20us to relax
the input impedance requirements.

Additionally, the phint0_ain and phint1_ain channels require a much
longer sampling period due to their specific circuit design. Increase
their sample times to 200us. Remove stale comments regarding clock
cycles that no longer match the updated timings.

Fixes: 8267753c891c ("ARM: dts: stm32: Add MECIO1 and MECT1S board variants")
Cc: <stable at vger.kernel.org>
Signed-off-by: David Jander <david at protonic.nl>
Co-developed-by: Oleksij Rempel <o.rempel at pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel at pengutronix.de>
---
 .../arm/boot/dts/st/stm32mp15x-mecio1-io.dtsi | 32 +++++++++----------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/arch/arm/boot/dts/st/stm32mp15x-mecio1-io.dtsi b/arch/arm/boot/dts/st/stm32mp15x-mecio1-io.dtsi
index 1ce01bac9814..1b1299770ca0 100644
--- a/arch/arm/boot/dts/st/stm32mp15x-mecio1-io.dtsi
+++ b/arch/arm/boot/dts/st/stm32mp15x-mecio1-io.dtsi
@@ -104,80 +104,79 @@ &adc1 {
 
 	channel at 0 {
 		reg = <0>;
-		/* 16.5 ck_cycles sampling time */
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "p24v_stp";
 	};
 
 	channel at 1 {
 		reg = <1>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "p24v_hpdcm";
 	};
 
 	channel at 2 {
 		reg = <2>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "ain0";
 	};
 
 	channel at 3 {
 		reg = <3>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpdcm1_i2";
 	};
 
 	channel at 5 {
 		reg = <5>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpout1_i";
 	};
 
 	channel at 6 {
 		reg = <6>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "ain1";
 	};
 
 	channel at 9 {
 		reg = <9>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpout0_i";
 	};
 
 	channel at 10 {
 		reg = <10>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <200000>;
 		label = "phint0_ain";
 	};
 
 	channel at 13 {
 		reg = <13>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <200000>;
 		label = "phint1_ain";
 	};
 
 	channel at 15 {
 		reg = <15>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpdcm0_i1";
 	};
 
 	channel at 16 {
 		reg = <16>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "lsin";
 	};
 
 	channel at 18 {
 		reg = <18>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpdcm0_i2";
 	};
 
 	channel at 19 {
 		reg = <19>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "hpdcm1_i1";
 	};
 };
@@ -187,14 +186,13 @@ &adc2 {
 
 	channel at 2 {
 		reg = <2>;
-		/* 16.5 ck_cycles sampling time */
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "ain2";
 	};
 
 	channel at 6 {
 		reg = <6>;
-		st,min-sample-time-ns = <5000>;
+		st,min-sample-time-ns = <20000>;
 		label = "ain3";
 	};
 };
-- 
2.47.3