stm32/adc: Get ADC working on STM32N6 MCUs.

Changes made here for N6 are:
- set RIF security attributes for ADC12
- clock ADC12 at 50MHz (maximum) so it runs at spec (max 5Msamp/sec)
- increase sampling time for standard channels to 46.5 cycles
- calibrate ADC in `adc.c`
- correctly clear ADC_CFGR1_RES bits in `machine_adc.c`
- set preselection register in `machine_adc.c`

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/adc.c

@@ -314,6 +314,11 @@ static void adcx_clock_enable(ADC_HandleTypeDef *adch) {
 static void adcx_init_periph(ADC_HandleTypeDef *adch, uint32_t resolution) {
     adcx_clock_enable(adch);
 
+    // Set ADC clock prescaler, if it's not done by HAL_ADC_Init() below.
+    #if defined(STM32N6)
+    LL_RCC_SetADCPrescaler(4 - 1); // 200MHz / 4 = 50MHz
+    #endif
+
     adch->Init.Resolution = resolution;
     adch->Init.ContinuousConvMode = DISABLE;
     adch->Init.DiscontinuousConvMode = DISABLE;
@@ -387,7 +392,7 @@ static void adcx_init_periph(ADC_HandleTypeDef *adch, uint32_t resolution) {
     #endif
     #if defined(STM32G0)
     HAL_ADCEx_Calibration_Start(adch);
-    #elif defined(STM32G4) || defined(STM32H5) || defined(STM32L4) || defined(STM32WB)
+    #elif defined(STM32G4) || defined(STM32H5) || defined(STM32L4) || defined(STM32N6) || defined(STM32WB)
     HAL_ADCEx_Calibration_Start(adch, ADC_SINGLE_ENDED);
     #endif
 }
@@ -461,7 +466,7 @@ static void adc_config_channel(ADC_HandleTypeDef *adc_handle, uint32_t channel)
     if (__HAL_ADC_IS_CHANNEL_INTERNAL(channel)) {
         sConfig.SamplingTime = ADC_SAMPLETIME_246CYCLES_5;
     } else {
-        sConfig.SamplingTime = ADC_SAMPLETIME_11CYCLES_5;
+        sConfig.SamplingTime = ADC_SAMPLETIME_46CYCLES_5;
     }
     sConfig.SingleDiff = ADC_SINGLE_ENDED;
     sConfig.OffsetNumber = ADC_OFFSET_NONE;

ports/stm32/machine_adc.c

@@ -86,7 +86,7 @@
 #define ADC_SAMPLETIME_DEFAULT      ADC_SAMPLETIME_12CYCLES_5
 #define ADC_SAMPLETIME_DEFAULT_INT  ADC_SAMPLETIME_247CYCLES_5
 #elif defined(STM32N6)
-#define ADC_SAMPLETIME_DEFAULT      ADC_SAMPLETIME_11CYCLES_5
+#define ADC_SAMPLETIME_DEFAULT      ADC_SAMPLETIME_46CYCLES_5
 #define ADC_SAMPLETIME_DEFAULT_INT  ADC_SAMPLETIME_246CYCLES_5
 #endif
 
@@ -232,6 +232,8 @@ void adc_config(ADC_TypeDef *adc, uint32_t bits) {
     ADC1_COMMON->CCR = 0; // ADCPR=PCLK/2
     #elif defined(STM32L1)
     ADC1_COMMON->CCR = 1 << ADC_CCR_ADCPRE_Pos; // ADCPRE=2
+    #elif defined(STM32N6)
+    LL_RCC_SetADCPrescaler(4 - 1); // 200MHz / 4 = 50MHz
     #elif defined(STM32WB)
     ADC1_COMMON->CCR = 0 << ADC_CCR_PRESC_Pos | 0 << ADC_CCR_CKMODE_Pos; // PRESC=1, MODE=ASYNC
     #elif defined(STM32WL)
@@ -324,7 +326,7 @@ void adc_config(ADC_TypeDef *adc, uint32_t bits) {
 
     #elif defined(STM32N6)
 
-    uint32_t cfgr1_clr = ADC_CFGR1_CONT | ADC_CFGR1_EXTEN;
+    uint32_t cfgr1_clr = ADC_CFGR1_CONT | ADC_CFGR1_EXTEN | ADC_CFGR1_RES;
     uint32_t cfgr1 = res << ADC_CFGR1_RES_Pos;
     adc->CFGR1 = (adc->CFGR1 & ~cfgr1_clr) | cfgr1;
 
@@ -439,13 +441,6 @@ static void adc_config_channel(ADC_TypeDef *adc, uint32_t channel, uint32_t samp
     #if defined(STM32G4) || defined(STM32H5) || defined(STM32H7A3xx) || defined(STM32H7A3xxQ) || defined(STM32H7B3xx) || defined(STM32H7B3xxQ) || defined(STM32N6)
     ADC_Common_TypeDef *adc_common = ADC12_COMMON;
     #elif defined(STM32H7)
-    #if defined(ADC_VER_V5_V90)
-    if (adc != ADC3) {
-        adc->PCSEL_RES0 |= 1 << channel;
-    }
-    #else
-    adc->PCSEL |= 1 << channel;
-    #endif
     ADC_Common_TypeDef *adc_common = adc == ADC3 ? ADC3_COMMON : ADC12_COMMON;
     #elif defined(STM32L4)
     ADC_Common_TypeDef *adc_common = ADCx_COMMON;
@@ -475,6 +470,7 @@ static void adc_config_channel(ADC_TypeDef *adc, uint32_t channel, uint32_t samp
         adc->OR |= ADC_OR_OP0; // Enable Vddcore channel on ADC2
     #endif
     }
+
     #if defined(STM32G4) || defined(STM32H5) || defined(STM32N6) || defined(STM32WB)
     // MCU uses encoded literals for internal channels -> extract ADC channel for following code
     if (__LL_ADC_IS_CHANNEL_INTERNAL(channel)) {
@@ -482,6 +478,17 @@ static void adc_config_channel(ADC_TypeDef *adc, uint32_t channel, uint32_t samp
     }
     adc->DIFSEL &= ~(1 << channel); // Set channel to Single-ended.
     #endif
+
+    #if defined(STM32H7) || defined(STM32N6)
+    #if defined(ADC_VER_V5_V90)
+    if (adc != ADC3) {
+        adc->PCSEL_RES0 |= 1 << channel;
+    }
+    #else
+    adc->PCSEL |= 1 << channel;
+    #endif
+    #endif
+
     adc->SQR1 = (channel & 0x1f) << ADC_SQR1_SQ1_Pos | (1 - 1) << ADC_SQR1_L_Pos;
     __IO uint32_t *smpr;
     if (channel <= 9) {

ports/stm32/main.c

@@ -316,6 +316,7 @@ static void risaf_init(void) {
     rimc_master.MasterCID = RIF_CID_1;
     rimc_master.SecPriv = RIF_ATTRIBUTE_SEC | RIF_ATTRIBUTE_PRIV;
 
+    HAL_RIF_RISC_SetSlaveSecureAttributes(RIF_RISC_PERIPH_INDEX_ADC12, RIF_ATTRIBUTE_SEC | RIF_ATTRIBUTE_PRIV);
     HAL_RIF_RIMC_ConfigMasterAttributes(RIF_MASTER_INDEX_SDMMC1, &rimc_master);
     HAL_RIF_RISC_SetSlaveSecureAttributes(RIF_RISC_PERIPH_INDEX_SDMMC1, RIF_ATTRIBUTE_SEC | RIF_ATTRIBUTE_PRIV);
     HAL_RIF_RIMC_ConfigMasterAttributes(RIF_MASTER_INDEX_SDMMC2, &rimc_master);