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From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: barebox@lists.infradead.org
Cc: Kim Christensen <kch@skov.dk>,
Ahmad Fatoum <a.fatoum@pengutronix.de>
Date: Mon, 14 Apr 2025 08:50:07 +0200
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Subject: [PATCH 4/6] ARM: i.MX8MP: skov: halt startup until power is good
X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000)
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The 24V regulator supplying the system can indicate via a GPIO imminent
voltage loss. The board's capacitors hold enough charge to power the system
a while longer in such a state, but eventually, unless external power is
restored, the brownout detection of the PMIC will kick in.
For the span of time between voltage drop detection and PMIC brownout,
let's detect this situation and delay startup. This way, Linux can
detect the ongoing voltage loss, power down the eMMC, reboot into
barebox and barebox will delay boot as long as the problem persists.
Co-developed-by: Kim Christensen <kch@skov.dk>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
arch/arm/boards/skov-imx8mp/lowlevel.c | 60 ++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
diff --git a/arch/arm/boards/skov-imx8mp/lowlevel.c b/arch/arm/boards/skov-imx8mp/lowlevel.c
index 637fc50b3f30..d7bd771f259d 100644
--- a/arch/arm/boards/skov-imx8mp/lowlevel.c
+++ b/arch/arm/boards/skov-imx8mp/lowlevel.c
@@ -20,6 +20,9 @@
extern char __dtb_z_imx8mp_skov_start[];
+#define PGOOD_PAD_CTRL MUX_PAD_CTRL(MX8MP_PAD_CTL_PUE | \
+ MX8MP_PAD_CTL_PE)
+
#define UART_PAD_CTRL MUX_PAD_CTRL(MX8MP_PAD_CTL_DSE6 | \
MX8MP_PAD_CTL_FSEL | \
MX8MP_PAD_CTL_PUE | \
@@ -30,6 +33,12 @@ extern char __dtb_z_imx8mp_skov_start[];
MX8MP_PAD_CTL_PUE | \
MX8MP_PAD_CTL_PE)
+static inline void led_d1_toggle(bool *on)
+{
+ imx8m_gpio_direction_output(IOMEM(MX8MP_GPIO1_BASE_ADDR), 5, *on);
+ *on = !*on;
+}
+
static void setup_uart(void)
{
void __iomem *uart = IOMEM(MX8M_UART2_BASE_ADDR);
@@ -67,6 +76,55 @@ static struct pmic_config pca9450_cfg[] = {
{ PCA9450_BUCK2OUT_DVS0, 0x14 },
};
+static inline bool power_good(void)
+{
+ /* IMX_SHDN_MF in schematics */
+ return imx8m_gpio_val(IOMEM(MX8MP_GPIO4_BASE_ADDR), 23);
+}
+
+static void wait_for_power_good(void)
+{
+ void __iomem *gpio4 = IOMEM(MX8MP_GPIO4_BASE_ADDR);
+ int timeout_ms = 0;
+ bool led_active = true;
+
+ imx8mp_setup_pad(MX8MP_PAD_SAI2_RXD0__GPIO4_IO23 | PGOOD_PAD_CTRL);
+ imx8m_gpio_direction_input(gpio4, 23);
+
+ led_d1_toggle(&led_active);
+
+ if (power_good())
+ return;
+
+ pr_warn("\nDelaying boot until power stabilizes\n");
+
+ /* If we reach this, because Linux did a hw_protection_reboot, we don't
+ * want to continue booting right away.
+ *
+ * Thus let's either wait for the condition to subscede or for voltage
+ * to reach a low enough level for the PMIC to detect VSYS_UVLO going
+ * lower than allowed
+ */
+
+ while (1) {
+ if (power_good()) {
+ /* wait 10ms longer and check if it still good */
+ udelay(10000);
+ if (power_good()) {
+ pr_info("IMX_SHDN_MF stuck low for ~%ums.\n", timeout_ms);
+ break;
+ }
+ }
+ /* fast blink LED D1 */
+ if (timeout_ms % 100 == 0) {
+ pr_debug(".");
+ led_d1_toggle(&led_active);
+ }
+ udelay(1000);
+ timeout_ms++;
+ }
+}
+
static void power_init_board(void)
{
struct pbl_i2c *i2c;
@@ -77,6 +135,8 @@ static void power_init_board(void)
imx8mp_setup_pad(MX8MP_PAD_SAI3_TXD__GPIO5_IO01);
imx8m_gpio_direction_output(IOMEM(MX8MP_GPIO5_BASE_ADDR), 1, 0);
+ wait_for_power_good();
+
imx8mp_setup_pad(MX8MP_PAD_I2C1_SCL__I2C1_SCL | I2C_PAD_CTRL);
imx8mp_setup_pad(MX8MP_PAD_I2C1_SDA__I2C1_SDA | I2C_PAD_CTRL);
--
2.39.5