board: stm32pm1: update USB-C power detection algorithm on DK boards

USB-C power supply which are Power Delivery compliant (USB-PD) are able
to provide different voltage/current (for example 5V/3A 9V/3A 12V/2.25A...)

In this case, the power supply need to negotiate the voltage/current to
use with the device using CC1/CC2 USB-C signals.

If this negotiation occurs during ADC measurement (done also on CC1/CC2
USB-C signals) some ADC acquisition can be corrupted which cause wrong
power supply current detection.

To avoid this, the power supply current detection algorithm is updated
as following:
  - perform an ADC measurement, if a 3A current is detected, continue the
    boot process.
  - else, wait 20ms (max tPDDebounce duration) to ensure that USB-PD
    negotiation is done and perform another ADC measurement.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>

diff --git a/board/st/stm32mp1/stm32mp1.c b/board/st/stm32mp1/stm32mp1.c
index 60e3a34..78362d2 100644 (file)
--- a/board/st/stm32mp1/stm32mp1.c
+++ b/board/st/stm32mp1/stm32mp1.c
@@ -289,41 +289,13 @@ static void __maybe_unused led_error_blink(u32 nb_blink)
                hang();
 }
 
-static int board_check_usb_power(void)
+static int adc_measurement(ofnode node, int adc_count, int *min_uV, int *max_uV)
 {
        struct ofnode_phandle_args adc_args;
        struct udevice *adc;
-       ofnode node;
        unsigned int raw;
-       int max_uV = 0;
-       int min_uV = USB_START_HIGH_THRESHOLD_UV;
-       int ret, uV, adc_count;
-       u32 nb_blink;
-       u8 i;
-
-       if (!IS_ENABLED(CONFIG_ADC))
-               return -ENODEV;
-
-       node = ofnode_path("/config");
-       if (!ofnode_valid(node)) {
-               log_debug("no /config node?\n");
-               return -ENOENT;
-       }
-
-       /*
-        * Retrieve the ADC channels devices and get measurement
-        * for each of them
-        */
-       adc_count = ofnode_count_phandle_with_args(node, "st,adc_usb_pd",
-                                                  "#io-channel-cells", 0);
-       if (adc_count < 0) {
-               if (adc_count == -ENOENT)
-                       return 0;
-
-               log_err("can't find adc channel (%d)\n", adc_count);
-
-               return adc_count;
-       }
+       int ret, uV;
+       int i;
 
        for (i = 0; i < adc_count; i++) {
                if (ofnode_parse_phandle_with_args(node, "st,adc_usb_pd",
@@ -350,10 +322,10 @@ static int board_check_usb_power(void)
                }
                /* Convert to uV */
                if (!adc_raw_to_uV(adc, raw, &uV)) {
-                       if (uV > max_uV)
-                               max_uV = uV;
-                       if (uV < min_uV)
-                               min_uV = uV;
+                       if (uV > *max_uV)
+                               *max_uV = uV;
+                       if (uV < *min_uV)
+                               *min_uV = uV;
                        log_debug("%s[%02d] = %u, %d uV\n",
                                  adc->name, adc_args.args[0], raw, uV);
                } else {
@@ -362,18 +334,66 @@ static int board_check_usb_power(void)
                }
        }
 
+       return 0;
+}
+
+static int board_check_usb_power(void)
+{
+       ofnode node;
+       int max_uV = 0;
+       int min_uV = USB_START_HIGH_THRESHOLD_UV;
+       int adc_count, ret;
+       u32 nb_blink;
+       u8 i;
+
+       node = ofnode_path("/config");
+       if (!ofnode_valid(node)) {
+               log_debug("no /config node?\n");
+               return -ENOENT;
+       }
+
        /*
-        * If highest value is inside 1.23 Volts and 2.10 Volts, that means
-        * board is plugged on an USB-C 3A power supply and boot process can
-        * continue.
+        * Retrieve the ADC channels devices and get measurement
+        * for each of them
         */
-       if (max_uV > USB_START_LOW_THRESHOLD_UV &&
-           max_uV <= USB_START_HIGH_THRESHOLD_UV &&
-           min_uV <= USB_LOW_THRESHOLD_UV)
-               return 0;
+       adc_count = ofnode_count_phandle_with_args(node, "st,adc_usb_pd",
+                                                  "#io-channel-cells", 0);
+       if (adc_count < 0) {
+               if (adc_count == -ENOENT)
+                       return 0;
 
-       log_notice("****************************************************\n");
+               log_err("Can't find adc channel (%d)\n", adc_count);
+
+               return adc_count;
+       }
+
+       /* perform maximum of 2 ADC measurements to detect power supply current */
+       for (i = 0; i < 2; i++) {
+               if (IS_ENABLED(CONFIG_ADC))
+                       ret = adc_measurement(node, adc_count, &min_uV, &max_uV);
+               else
+                       ret = -ENODEV;
 
+               if (ret)
+                       return ret;
+
+               /*
+                * If highest value is inside 1.23 Volts and 2.10 Volts, that means
+                * board is plugged on an USB-C 3A power supply and boot process can
+                * continue.
+                */
+               if (max_uV > USB_START_LOW_THRESHOLD_UV &&
+                   max_uV <= USB_START_HIGH_THRESHOLD_UV &&
+                   min_uV <= USB_LOW_THRESHOLD_UV)
+                       return 0;
+
+               if (i == 0) {
+                       log_err("Previous ADC measurements was not the one expected, retry in 20ms\n");
+                       mdelay(20);  /* equal to max tPDDebounce duration (min 10ms - max 20ms) */
+               }
+       }
+
+       log_notice("****************************************************\n");
        /*
         * If highest and lowest value are either both below
         * USB_LOW_THRESHOLD_UV or both above USB_LOW_THRESHOLD_UV, that