[PATCH 3/4] rtc: stm32: add Low Speed Clock Output (LSCO) support

From: Valentin Caron
Date: Thu Jul 11 2024 - 10:11:17 EST

RTC is able to output on a pin the "LSE" internal clock.

STM32 RTC is now registered as a clock provider.
It provides rtc_lsco clock, that means RTC_LSCO is output on either
RTC_OUT1 or RTC_OUT2_RMP, depending on pinmux DT property.
The clock is marked as CLK_IGNORE_UNUSED and CLK_IS_CRITICAL because
RTC_LSCO can be early required by devices needed it to init.

Add LSCO in pinmux functions.

Add "stm32_rtc_clean_outs" to disable LSCO. As RTC is part of "backup"
power domain, it is not reset during shutdown or reboot. So force LSCO
disable at probe.

Co-developed-by: Amelie Delaunay <amelie.delaunay@xxxxxxxxxxx>
Signed-off-by: Amelie Delaunay <amelie.delaunay@xxxxxxxxxxx>
Signed-off-by: Valentin Caron <valentin.caron@xxxxxxxxxxx>
---
drivers/rtc/Kconfig | 1 +
drivers/rtc/rtc-stm32.c | 101 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+)

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 2a95b05982ad..9ee51cd67b22 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1922,6 +1922,7 @@ config RTC_DRV_R7301
config RTC_DRV_STM32
tristate "STM32 RTC"
select REGMAP_MMIO
+ depends on COMMON_CLK
depends on ARCH_STM32 || COMPILE_TEST
help
If you say yes here you get support for the STM32 On-Chip
diff --git a/drivers/rtc/rtc-stm32.c b/drivers/rtc/rtc-stm32.c
index c1e69c5b27bd..a57d494b229c 100644
--- a/drivers/rtc/rtc-stm32.c
+++ b/drivers/rtc/rtc-stm32.c
@@ -7,6 +7,7 @@
#include <linux/bcd.h>
#include <linux/bitfield.h>
#include <linux/clk.h>
+#include <linux/clk-provider.h>
#include <linux/errno.h>
#include <linux/iopoll.h>
#include <linux/ioport.h>
@@ -45,6 +46,10 @@
#define STM32_RTC_CR_FMT BIT(6)
#define STM32_RTC_CR_ALRAE BIT(8)
#define STM32_RTC_CR_ALRAIE BIT(12)
+#define STM32_RTC_CR_OSEL GENMASK(22, 21)
+#define STM32_RTC_CR_COE BIT(23)
+#define STM32_RTC_CR_TAMPOE BIT(26)
+#define STM32_RTC_CR_OUT2EN BIT(31)

/* STM32_RTC_ISR/STM32_RTC_ICSR bit fields */
#define STM32_RTC_ISR_ALRAWF BIT(0)
@@ -81,6 +86,12 @@
/* STM32_RTC_SR/_SCR bit fields */
#define STM32_RTC_SR_ALRA BIT(0)

+/* STM32_RTC_CFGR bit fields */
+#define STM32_RTC_CFGR_OUT2_RMP BIT(0)
+#define STM32_RTC_CFGR_LSCOEN GENMASK(2, 1)
+#define STM32_RTC_CFGR_LSCOEN_OUT1 1
+#define STM32_RTC_CFGR_LSCOEN_OUT2_RMP 2
+
/* STM32_RTC_VERR bit fields */
#define STM32_RTC_VERR_MINREV_SHIFT 0
#define STM32_RTC_VERR_MINREV GENMASK(3, 0)
@@ -130,6 +141,7 @@ struct stm32_rtc_registers {
u16 wpr;
u16 sr;
u16 scr;
+ u16 cfgr;
u16 verr;
};

@@ -145,6 +157,7 @@ struct stm32_rtc_data {
bool need_dbp;
bool need_accuracy;
bool rif_protected;
+ bool has_lsco;
};

struct stm32_rtc {
@@ -157,6 +170,7 @@ struct stm32_rtc {
struct clk *rtc_ck;
const struct stm32_rtc_data *data;
int irq_alarm;
+ struct clk *clk_lsco;
};

struct stm32_rtc_rif_resource {
@@ -231,7 +245,68 @@ struct stm32_rtc_pinmux_func {
int (*action)(struct pinctrl_dev *pctl_dev, unsigned int pin);
};

+static int stm32_rtc_pinmux_lsco_available(struct pinctrl_dev *pctldev, unsigned int pin)
+{
+ struct stm32_rtc *rtc = pinctrl_dev_get_drvdata(pctldev);
+ struct stm32_rtc_registers regs = rtc->data->regs;
+ unsigned int cr = readl_relaxed(rtc->base + regs.cr);
+ unsigned int cfgr = readl_relaxed(rtc->base + regs.cfgr);
+ unsigned int calib = STM32_RTC_CR_COE;
+ unsigned int tampalrm = STM32_RTC_CR_TAMPOE | STM32_RTC_CR_OSEL;
+
+ switch (pin) {
+ case OUT1:
+ if ((!(cr & STM32_RTC_CR_OUT2EN) &&
+ ((cr & calib) || cr & tampalrm)) ||
+ ((cr & calib) && (cr & tampalrm)))
+ return -EBUSY;
+ break;
+ case OUT2_RMP:
+ if ((cr & STM32_RTC_CR_OUT2EN) &&
+ (cfgr & STM32_RTC_CFGR_OUT2_RMP) &&
+ ((cr & calib) || (cr & tampalrm)))
+ return -EBUSY;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (clk_get_rate(rtc->rtc_ck) != 32768)
+ return -ERANGE;
+
+ return 0;
+}
+
+static int stm32_rtc_pinmux_action_lsco(struct pinctrl_dev *pctldev, unsigned int pin)
+{
+ struct stm32_rtc *rtc = pinctrl_dev_get_drvdata(pctldev);
+ struct stm32_rtc_registers regs = rtc->data->regs;
+ struct device *dev = rtc->rtc_dev->dev.parent;
+ u8 lscoen;
+ int ret;
+
+ if (!rtc->data->has_lsco)
+ return -EPERM;
+
+ ret = stm32_rtc_pinmux_lsco_available(pctldev, pin);
+ if (ret)
+ return ret;
+
+ lscoen = (pin == OUT1) ? STM32_RTC_CFGR_LSCOEN_OUT1 : STM32_RTC_CFGR_LSCOEN_OUT2_RMP;
+
+ rtc->clk_lsco = clk_register_gate(dev, "rtc_lsco", __clk_get_name(rtc->rtc_ck),
+ CLK_IGNORE_UNUSED | CLK_IS_CRITICAL,
+ rtc->base + regs.cfgr, lscoen, 0, NULL);
+ if (IS_ERR(rtc->clk_lsco))
+ return PTR_ERR(rtc->clk_lsco);
+
+ of_clk_add_provider(dev->of_node, of_clk_src_simple_get, rtc->clk_lsco);
+
+ return 0;
+}
+
static const struct stm32_rtc_pinmux_func stm32_rtc_pinmux_functions[] = {
+ STM32_RTC_PINMUX("lsco", &stm32_rtc_pinmux_action_lsco, "out1", "out2_rmp"),
};

static int stm32_rtc_pinmux_get_functions_count(struct pinctrl_dev *pctldev)
@@ -687,6 +762,7 @@ static const struct stm32_rtc_data stm32_rtc_data = {
.need_dbp = true,
.need_accuracy = false,
.rif_protected = false,
+ .has_lsco = false,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -697,6 +773,7 @@ static const struct stm32_rtc_data stm32_rtc_data = {
.wpr = 0x24,
.sr = 0x0C, /* set to ISR offset to ease alarm management */
.scr = UNDEF_REG,
+ .cfgr = UNDEF_REG,
.verr = UNDEF_REG,
},
.events = {
@@ -710,6 +787,7 @@ static const struct stm32_rtc_data stm32h7_rtc_data = {
.need_dbp = true,
.need_accuracy = false,
.rif_protected = false,
+ .has_lsco = false,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -720,6 +798,7 @@ static const struct stm32_rtc_data stm32h7_rtc_data = {
.wpr = 0x24,
.sr = 0x0C, /* set to ISR offset to ease alarm management */
.scr = UNDEF_REG,
+ .cfgr = UNDEF_REG,
.verr = UNDEF_REG,
},
.events = {
@@ -742,6 +821,7 @@ static const struct stm32_rtc_data stm32mp1_data = {
.need_dbp = false,
.need_accuracy = true,
.rif_protected = false,
+ .has_lsco = true,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -752,6 +832,7 @@ static const struct stm32_rtc_data stm32mp1_data = {
.wpr = 0x24,
.sr = 0x50,
.scr = 0x5C,
+ .cfgr = 0x60,
.verr = 0x3F4,
},
.events = {
@@ -765,6 +846,7 @@ static const struct stm32_rtc_data stm32mp25_data = {
.need_dbp = false,
.need_accuracy = true,
.rif_protected = true,
+ .has_lsco = true,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -775,6 +857,7 @@ static const struct stm32_rtc_data stm32mp25_data = {
.wpr = 0x24,
.sr = 0x50,
.scr = 0x5C,
+ .cfgr = 0x60,
.verr = 0x3F4,
},
.events = {
@@ -792,6 +875,19 @@ static const struct of_device_id stm32_rtc_of_match[] = {
};
MODULE_DEVICE_TABLE(of, stm32_rtc_of_match);

+static void stm32_rtc_clean_outs(struct stm32_rtc *rtc)
+{
+ struct stm32_rtc_registers regs = rtc->data->regs;
+
+ if (regs.cfgr != UNDEF_REG) {
+ unsigned int cfgr = readl_relaxed(rtc->base + regs.cfgr);
+
+ cfgr &= ~STM32_RTC_CFGR_LSCOEN;
+ cfgr &= ~STM32_RTC_CFGR_OUT2_RMP;
+ writel_relaxed(cfgr, rtc->base + regs.cfgr);
+ }
+}
+
static int stm32_rtc_check_rif(struct stm32_rtc *stm32_rtc,
struct stm32_rtc_rif_resource res)
{
@@ -1024,6 +1120,8 @@ static int stm32_rtc_probe(struct platform_device *pdev)
goto err;
}

+ stm32_rtc_clean_outs(rtc);
+
ret = devm_pinctrl_register_and_init(&pdev->dev, &stm32_rtc_pdesc, rtc, &pctl);
if (ret)
return dev_err_probe(&pdev->dev, ret, "pinctrl register failed");
@@ -1070,6 +1168,9 @@ static void stm32_rtc_remove(struct platform_device *pdev)
const struct stm32_rtc_registers *regs = &rtc->data->regs;
unsigned int cr;

+ if (!IS_ERR_OR_NULL(rtc->clk_lsco))
+ clk_unregister_gate(rtc->clk_lsco);
+
/* Disable interrupts */
stm32_rtc_wpr_unlock(rtc);
cr = readl_relaxed(rtc->base + regs->cr);
--
2.25.1