[l1] rcc: support MSI clocking

Some new definitions and helpers.  Main change really that the list of
preconfigured clock configs is no longer restricted to HSI/PLL

include/libopencm3/stm32/l1/rcc.h

@@ -82,11 +82,31 @@ LGPL License Terms @ref lgpl_license
 #define RCC_CR_RTCPRE_DIV2	0
 #define RCC_CR_RTCPRE_DIV4	1
 #define RCC_CR_RTCPRE_DIV8	2
-#define RCC_CR_RTCPRE_DIV18	3
+#define RCC_CR_RTCPRE_DIV16	3
+#define RCC_CR_RTCPRE_SHIFT	29
+#define RCC_CR_RTCPRE_MASK	0x3
 
 /* --- RCC_ICSCR values ---------------------------------------------------- */
 
-// TODO
+#define RCC_ICSCR_MSITRIM_SHIFT		24
+#define RCC_ICSCR_MSITRIM_MASK		0xff
+#define RCC_ICSCR_MSICAL_SHIFT		16
+#define RCC_ICSCR_MSICAL_MASK		0xff
+
+#define RCC_ICSCR_MSIRANGE_SHIFT	13
+#define RCC_ICSCR_MSIRANGE_MASK		0x7
+#define RCC_ICSCR_MSIRANGE_65KHZ	0x0
+#define RCC_ICSCR_MSIRANGE_131KHZ	0x1
+#define RCC_ICSCR_MSIRANGE_262KHZ	0x2
+#define RCC_ICSCR_MSIRANGE_524KHZ	0x3
+#define RCC_ICSCR_MSIRANGE_1MHZ		0x4
+#define RCC_ICSCR_MSIRANGE_2MHZ		0x5
+#define RCC_ICSCR_MSIRANGE_4MHZ		0x6
+
+#define RCC_ICSCR_HSITRIM_SHIFT		8
+#define RCC_ICSCR_HSITRIM_MASK		0x1f
+#define RCC_ICSCR_HSICAL_SHIFT		0
+#define RCC_ICSCR_HSICAL_MASK		0xff
 
 /* --- RCC_CFGR values ----------------------------------------------------- */
 
@@ -347,7 +367,14 @@ LGPL License Terms @ref lgpl_license
 #define RCC_CSR_RMVF				(1 << 24)
 #define RCC_CSR_RTCRST				(1 << 23)
 #define RCC_CSR_RTCEN				(1 << 22)
-/* RTCSEL[1:0] */
+#define RCC_CSR_RTCSEL_SHIFT			(16)
+#define RCC_CSR_RTCSEL_MASK			(0x3)
+#define RCC_CSR_RTCSEL_NONE			(0x0)
+#define RCC_CSR_RTCSEL_LSE			(0x1)
+#define RCC_CSR_RTCSEL_LSI			(0x2)
+#define RCC_CSR_RTCSEL_HSI			(0x3)
+#define RCC_CSR_LSECSSD				(1 << 12)
+#define RCC_CSR_LSECSSON			(1 << 11)
 #define RCC_CSR_LSEBYP				(1 << 10)
 #define RCC_CSR_LSERDY				(1 << 9)
 #define RCC_CSR_LSEON				(1 << 8)
@@ -365,16 +392,20 @@ typedef struct {
 	vos_scale_t voltage_scale;
 	uint32_t apb1_frequency;
 	uint32_t apb2_frequency;
+	uint8_t msi_range;
 } clock_scale_t;
 
 typedef enum {
 	CLOCK_VRANGE1_HSI_PLL_24MHZ,
 	CLOCK_VRANGE1_HSI_PLL_32MHZ,
 	CLOCK_VRANGE1_HSI_RAW_16MHZ,
-	CLOCK_VRANGE1_END
-} clock_volt_range1_t;
+	CLOCK_VRANGE1_HSI_RAW_4MHZ,
+	CLOCK_VRANGE1_MSI_RAW_4MHZ,
+	CLOCK_VRANGE1_MSI_RAW_2MHZ,
+	CLOCK_CONFIG_END
+} clock_config_entry_t;
 
-extern const clock_scale_t clock_vrange1_config[CLOCK_VRANGE1_END];
+extern const clock_scale_t clock_config[CLOCK_CONFIG_END];
 
 
 /* --- Variable definitions ------------------------------------------------ */
@@ -413,6 +444,7 @@ void rcc_set_ppre1(u32 ppre1);
 void rcc_set_hpre(u32 hpre);
 void rcc_set_usbpre(u32 usbpre);
 u32 rcc_get_system_clock_source(int i);
+void rcc_clock_setup_msi(const clock_scale_t *clock);
 void rcc_clock_setup_hsi(const clock_scale_t *clock);
 void rcc_clock_setup_pll(const clock_scale_t *clock);
 void rcc_backupdomain_reset(void);

lib/stm32/l1/rcc.c

@@ -29,7 +29,8 @@
 u32 rcc_ppre1_frequency = 2097000;
 u32 rcc_ppre2_frequency = 2097000;
 
-const clock_scale_t clock_vrange1_config[CLOCK_VRANGE1_END] ={
+const clock_scale_t clock_config[CLOCK_CONFIG_END] =
+{
 	{ /* 24MHz PLL from HSI */
 		.pll_source = RCC_CFGR_PLLSRC_HSI_CLK,
 		.pll_mul = RCC_CFGR_PLLMUL_MUL3,
@@ -63,6 +64,35 @@ const clock_scale_t clock_vrange1_config[CLOCK_VRANGE1_END] ={
 		.apb1_frequency = 16000000,
 		.apb2_frequency = 16000000,
 	},
+	{ /* 4MHz HSI raw */
+		.hpre = RCC_CFGR_HPRE_SYSCLK_DIV4,
+		.ppre1 = RCC_CFGR_PPRE1_HCLK_NODIV,
+		.ppre2 = RCC_CFGR_PPRE2_HCLK_NODIV,
+		.voltage_scale = RANGE1,
+		.flash_config = FLASH_LATENCY_0WS,
+		.apb1_frequency = 4000000,
+		.apb2_frequency = 4000000,
+	},
+	{ /* 4MHz MSI raw */
+		.hpre = RCC_CFGR_HPRE_SYSCLK_NODIV,
+		.ppre1 = RCC_CFGR_PPRE1_HCLK_NODIV,
+		.ppre2 = RCC_CFGR_PPRE2_HCLK_NODIV,
+		.voltage_scale = RANGE1,
+		.flash_config = FLASH_LATENCY_0WS,
+		.apb1_frequency = 4194000,
+		.apb2_frequency = 4194000,
+		.msi_range = RCC_ICSCR_MSIRANGE_4MHZ,
+	},
+	{ /* 2MHz MSI raw */
+		.hpre = RCC_CFGR_HPRE_SYSCLK_NODIV,
+		.ppre1 = RCC_CFGR_PPRE1_HCLK_NODIV,
+		.ppre2 = RCC_CFGR_PPRE2_HCLK_NODIV,
+		.voltage_scale = RANGE1,
+		.flash_config = FLASH_LATENCY_0WS,
+		.apb1_frequency = 2097000,
+		.apb2_frequency = 2097000,
+		.msi_range = RCC_ICSCR_MSIRANGE_2MHZ,
+	},
 };
 
 void rcc_osc_ready_int_clear(osc_t osc)
@@ -407,6 +437,42 @@ u32 rcc_system_clock_source(void)
 	return ((RCC_CFGR & 0x000c) >> 2);
 }
 
+void rcc_clock_setup_msi(const clock_scale_t *clock)
+{
+	/* Enable internal multi-speed oscillator. */
+
+	u32 reg = RCC_ICSCR;
+	reg &= ~(RCC_ICSCR_MSIRANGE_MASK << RCC_ICSCR_MSIRANGE_SHIFT);
+	reg |= (clock->msi_range << RCC_ICSCR_MSIRANGE_SHIFT);
+	RCC_ICSCR = reg;
+
+	rcc_osc_on(MSI);
+	rcc_wait_for_osc_ready(MSI);
+
+	/* Select MSI as SYSCLK source. */
+	rcc_set_sysclk_source(RCC_CFGR_SW_SYSCLKSEL_MSICLK);
+
+	/*
+	 * Set prescalers for AHB, ADC, ABP1, ABP2.
+	 * Do this before touching the PLL (TODO: why?).
+	 */
+	rcc_set_hpre(clock->hpre);
+	rcc_set_ppre1(clock->ppre1);
+	rcc_set_ppre2(clock->ppre2);
+
+	pwr_set_vos_scale(clock->voltage_scale);
+
+	// I guess this should be in the settings?
+	flash_64bit_enable();
+	flash_prefetch_enable();
+	/* Configure flash settings. */
+	flash_set_ws(clock->flash_config);
+
+	/* Set the peripheral clock frequencies used. */
+	rcc_ppre1_frequency = clock->apb1_frequency;
+	rcc_ppre2_frequency = clock->apb2_frequency;
+}
+
 void rcc_clock_setup_hsi(const clock_scale_t *clock)
 {
 	/* Enable internal high-speed oscillator. */