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Subject[PATCH 3/6] rtc: stm32: add Low Speed Clock Output (LSCO) support
Date
From: Amelie Delaunay <amelie.delaunay@foss.st.com>

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 st,lsco DT property
(PC13 or PI8 on stm32mp15), (PC13 or PI1 on stm32mp13).

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
---
drivers/rtc/Kconfig | 1 +
drivers/rtc/rtc-stm32.c | 133 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 134 insertions(+)

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 41c65b4d2baf..2e8021d7c98a 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1888,6 +1888,7 @@ 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 ac9e228b56d0..ace041eb44b8 100644
--- a/drivers/rtc/rtc-stm32.c
+++ b/drivers/rtc/rtc-stm32.c
@@ -6,6 +6,7 @@

#include <linux/bcd.h>
#include <linux/clk.h>
+#include <linux/clk-provider.h>
#include <linux/iopoll.h>
#include <linux/ioport.h>
#include <linux/mfd/syscon.h>
@@ -15,6 +16,8 @@
#include <linux/regmap.h>
#include <linux/rtc.h>

+#include <dt-bindings/rtc/rtc-stm32.h>
+
#define DRIVER_NAME "stm32_rtc"

/* STM32_RTC_TR bit fields */
@@ -39,6 +42,11 @@
#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_COSEL BIT(19)
+#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)
@@ -75,6 +83,12 @@
/* 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)
@@ -89,6 +103,9 @@
/* Max STM32 RTC register offset is 0x3FC */
#define UNDEF_REG 0xFFFF

+/* Frequency of HSE clock (Hz) */
+#define STM32_RTC_HSE_FREQ 32768
+
struct stm32_rtc;

struct stm32_rtc_registers {
@@ -101,6 +118,7 @@ struct stm32_rtc_registers {
u16 wpr;
u16 sr;
u16 scr;
+ u16 cfgr;
u16 verr;
};

@@ -115,6 +133,7 @@ struct stm32_rtc_data {
bool has_pclk;
bool need_dbp;
bool has_wakeirq;
+ bool has_lsco;
};

struct stm32_rtc {
@@ -128,8 +147,88 @@ struct stm32_rtc {
const struct stm32_rtc_data *data;
int irq_alarm;
int wakeirq_alarm;
+ int lsco;
+ struct clk *clk_lsco;
};

+/*
+ * -------------------------------------------------------------------------
+ * | TAMPOE | OSEL[1:0] | COE | OUT2EN | RTC_OUT1 | RTC_OUT2 |
+ * | | | | | | or RTC_OUT2_RMP |
+ * |-------------------------------------------------------------------------|
+ * | 0 | 00 | 0 | 0 or 1 | - | - |
+ * |--------|-----------|-----|--------|------------------|------------------|
+ * | 0 | 00 | 1 | 0 | CALIB | - |
+ * |--------|-----------|-----|--------|------------------|------------------|
+ * | 0 or 1 | !=00 | 0 | 0 | TAMPALRM | - |
+ * |--------|-----------|-----|--------|------------------|------------------|
+ * | 0 | 00 | 1 | 1 | - | CALIB |
+ * |--------|-----------|-----|--------|------------------|------------------|
+ * | 0 or 1 | !=00 | 0 | 1 | - | TAMPALRM |
+ * |--------|-----------|-----|--------|------------------|------------------|
+ * | 0 or 1 | !=00 | 1 | 1 | TAMPALRM | CALIB |
+ * -------------------------------------------------------------------------
+ */
+static int stm32_rtc_clk_lsco_check_availability(struct stm32_rtc *rtc)
+{
+ 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 (rtc->lsco) {
+ case RTC_OUT1:
+ if ((!(cr & STM32_RTC_CR_OUT2EN) &&
+ ((cr & calib) || cr & tampalrm)) ||
+ ((cr & calib) && (cr & tampalrm)))
+ return -EBUSY;
+ break;
+ case RTC_OUT2_RMP:
+ if ((cr & STM32_RTC_CR_OUT2EN) &&
+ (cfgr & STM32_RTC_CFGR_OUT2_RMP) &&
+ ((cr & calib) || (cr & tampalrm)))
+ return -EBUSY;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* LSCO can only work if RTC clock source is HSE */
+ if (clk_get_rate(rtc->rtc_ck) != STM32_RTC_HSE_FREQ)
+ return -ERANGE;
+
+ return 0;
+}
+
+static int stm32_rtc_clk_lsco_register(struct platform_device *pdev)
+{
+ struct stm32_rtc *rtc = platform_get_drvdata(pdev);
+ struct stm32_rtc_registers regs = rtc->data->regs;
+ u8 lscoen;
+ int ret;
+
+ ret = stm32_rtc_clk_lsco_check_availability(rtc);
+ if (ret)
+ return ret;
+
+ lscoen = (rtc->lsco == RTC_OUT1) ? STM32_RTC_CFGR_LSCOEN_OUT1 :
+ STM32_RTC_CFGR_LSCOEN_OUT2_RMP;
+
+ rtc->clk_lsco = clk_register_gate(&pdev->dev, "rtc_lsco",
+ __clk_get_name(rtc->rtc_ck),
+ 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(pdev->dev.of_node,
+ of_clk_src_simple_get, rtc->clk_lsco);
+
+ return 0;
+}
+
static void stm32_rtc_wpr_unlock(struct stm32_rtc *rtc)
{
const struct stm32_rtc_registers *regs = &rtc->data->regs;
@@ -145,6 +244,15 @@ static void stm32_rtc_wpr_lock(struct stm32_rtc *rtc)
writel_relaxed(RTC_WPR_WRONG_KEY, rtc->base + regs->wpr);
}

+static void stm32_rtc_clk_lsco_disable(struct platform_device *pdev)
+{
+ struct stm32_rtc *rtc = platform_get_drvdata(pdev);
+ struct stm32_rtc_registers regs = rtc->data->regs;
+ unsigned int cfgr = readl_relaxed(rtc->base + regs.cfgr);
+
+ writel_relaxed(cfgr &= ~STM32_RTC_CFGR_LSCOEN, rtc->base + regs.cfgr);
+}
+
static int stm32_rtc_enter_init_mode(struct stm32_rtc *rtc)
{
const struct stm32_rtc_registers *regs = &rtc->data->regs;
@@ -548,6 +656,7 @@ static const struct stm32_rtc_data stm32_rtc_data = {
.has_pclk = false,
.need_dbp = true,
.has_wakeirq = false,
+ .has_lsco = false,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -558,6 +667,7 @@ 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 = {
@@ -570,6 +680,7 @@ static const struct stm32_rtc_data stm32h7_rtc_data = {
.has_pclk = true,
.need_dbp = true,
.has_wakeirq = false,
+ .has_lsco = false,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -580,6 +691,7 @@ 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 = {
@@ -601,6 +713,7 @@ static const struct stm32_rtc_data stm32mp1_data = {
.has_pclk = true,
.need_dbp = false,
.has_wakeirq = true,
+ .has_lsco = true,
.regs = {
.tr = 0x00,
.dr = 0x04,
@@ -611,6 +724,7 @@ static const struct stm32_rtc_data stm32mp1_data = {
.wpr = 0x24,
.sr = 0x50,
.scr = 0x5C,
+ .cfgr = 0x60,
.verr = 0x3F4,
},
.events = {
@@ -814,6 +928,22 @@ static int stm32_rtc_probe(struct platform_device *pdev)
goto err;
}

+ if (rtc->data->has_lsco) {
+ ret = of_property_read_s32(pdev->dev.of_node,
+ "st,lsco", &rtc->lsco);
+ if (!ret) {
+ ret = stm32_rtc_clk_lsco_register(pdev);
+ if (ret)
+ dev_warn(&pdev->dev,
+ "LSCO clock registration failed: %d\n",
+ ret);
+ } else {
+ stm32_rtc_clk_lsco_disable(pdev);
+ rtc->lsco = ret;
+ dev_dbg(&pdev->dev, "No LSCO clock: %d\n", ret);
+ }
+ }
+
/*
* If INITS flag is reset (calendar year field set to 0x00), calendar
* must be initialized
@@ -852,6 +982,9 @@ static int 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
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