openwrt/target/linux/bcm27xx/patches-6.6/950-0560-drivers-hwmon-rp1-adc-check-conversion-validity-befo.patch

From 78fc5f683ee0e54489fa0022e920d07db237bd78 Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.com>
Date: Thu, 4 May 2023 15:48:53 +0100
Subject: [PATCH 0560/1085] drivers: hwmon: rp1-adc: check conversion validity
 before supplying value

The SAR ADC architecture may complete a conversion but instability in the
comparator can corrupt the result. Such corruption is signalled in the CS
ERR bit, asserted alongside each conversion result.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
---
 drivers/hwmon/rp1-adc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/hwmon/rp1-adc.c
+++ b/drivers/hwmon/rp1-adc.c
@@ -97,8 +97,14 @@ static int rp1_adc_read(struct rp1_adc_d
 	       data->base + RP1_ADC_RWTYPE_SET + RP1_ADC_CS);
 
 	ret = rp1_adc_ready_wait(data);
-	if (!ret)
-		*val = readl(data->base + RP1_ADC_RESULT);
+	if (ret)
+		return ret;
+
+	/* Asserted if the completed conversion had a convergence error */
+	if (readl(data->base + RP1_ADC_CS) & RP1_ADC_CS_ERR)
+		return -EIO;
+
+	*val = readl(data->base + RP1_ADC_RESULT);
 
 	spin_unlock(&data->lock);