Revert "nissa: Workaround for ADC initial read error"

This reverts commit 5e4df0a.

Reason for revert: Root cause of ADC issue fixed.

Original change's description:
> nissa: Workaround for ADC initial read error
>
> It appears the ADC comparator initialisation breaks
> other ADCs that have not been read, so workaround
> the issue by initially reading all ADCs so that they are correctly
> initialised.
>
> Also add a check so that zero reads are detected and returned as an
> error.
>
> BUG=b:224900226
> TEST=zmake build nivviks; flash and run and check ADCs work.
> BRANCH=none
>
> Signed-off-by: Andrew McRae <amcrae@google.com>
> Change-Id: Ifcbebf2ca9b9a336f10fe3659fd3452223474ed3
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3528015
> Reviewed-by: Peter Marheine <pmarheine@chromium.org>
> Commit-Queue: Peter Marheine <pmarheine@chromium.org>

Bug: b:224900226
Change-Id: I97e3b71270767571eebbbe850ba18d5a3cc2869a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3541803
Auto-Submit: Andrew McRae <amcrae@google.com>
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
Tested-by: Andrew McRae <amcrae@google.com>
Commit-Queue: Andrew McRae <amcrae@google.com>

Author: Andrew McRae

zephyr/projects/nissa/src/nivviks/board_config.c

@@ -10,7 +10,6 @@
 #include <kernel.h>
 #include <sys/printk.h>
 
-#include "adc.h"
 #include "driver/charger/isl923x_public.h"
 #include "driver/retimer/anx7483_public.h"
 #include "gpio/gpio_int.h"
@@ -79,14 +78,6 @@ static void nivviks_subboard_init(void)
 		gpio_pin_configure_dt(GPIO_DT_FROM_ALIAS(gpio_hpd_odl),
 				      GPIO_INPUT);
 	}
-	/*
-	 * Workaround for b/224900226.
-	 * Read all ADCs so that they are initialised.
-	 * TODO(b/224900226): Remove when fixed.
-	 */
-	for (enum adc_channel adc = 0; adc < ADC_CH_COUNT; adc++) {
-		adc_read_channel(adc);
-	}
 }
 DECLARE_HOOK(HOOK_INIT, nivviks_subboard_init, HOOK_PRIO_FIRST+1);
 

zephyr/shim/src/adc.c

@@ -82,16 +82,5 @@ int adc_read_channel(enum adc_channel ch)
 			      ADC_GAIN_1, CONFIG_PLATFORM_EC_ADC_RESOLUTION,
 			      &ret);
 	ret = (ret * adc_channels[ch].factor_mul) / adc_channels[ch].factor_div;
-#ifdef CONFIG_BOARD_NIVVIKS
-	/*
-	 * TODO(b/224900226): Remove when fixed.
-	 * Temporary workaround for b/224900226, where
-	 * the temperature ADCs sometimes read zero.
-	 */
-	if (ret == 0) {
-		LOG_ERR("Zero read on sensor %d, ignored", ch);
-		return -1;
-	}
-#endif
 	return ret;
 }