stmhal: Improve flash storage cache management.

Internal flash used for the filesystem is now written (from the cache)
only after a 5s delay, or when a file is closed, or when the drive is
unmounted from the host.  This delay means that multiple writes can
accumulate in the cache, and leads to less writes to the flash, making
it last longer.

It's implemented by a high-priority interrupt that takes care of flash
erase and write, and flushing the cache.

This is still only an interim solution for the flash filesystem.  It
eventually needs to be replaced with something that uses less RAM for
the cache, something that can use more of the flash, and something that
does proper wear levelling.

stmhal/flash.c

@@ -49,7 +49,7 @@ uint32_t flash_get_sector_info(uint32_t addr, uint32_t *start_addr, uint32_t *si
     return 0;
 }
 
-void flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32) {
+void flash_erase(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32) {
     // check there is something to write
     if (num_word32 == 0) {
         return;
@@ -71,13 +71,46 @@ void flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32)
     uint32_t SectorError = 0;
     if (HAL_FLASHEx_Erase(&EraseInitStruct, &SectorError) != HAL_OK) {
         // error occurred during sector erase
+        HAL_FLASH_Lock(); // lock the flash
+        return;
+    }
+}
+
+/*
+// erase the sector using an interrupt
+void flash_erase_it(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32) {
+    // check there is something to write
+    if (num_word32 == 0) {
         return;
     }
 
+    // unlock
+    HAL_FLASH_Unlock();
+
+    // Clear pending flags (if any)
+    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_EOP | FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR |
+                           FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR|FLASH_FLAG_PGSERR);
+
+    // erase the sector(s)
+    FLASH_EraseInitTypeDef EraseInitStruct;
+    EraseInitStruct.TypeErase = TYPEERASE_SECTORS;
+    EraseInitStruct.VoltageRange = VOLTAGE_RANGE_3; // voltage range needs to be 2.7V to 3.6V
+    EraseInitStruct.Sector = flash_get_sector_info(flash_dest, NULL, NULL);
+    EraseInitStruct.NbSectors = flash_get_sector_info(flash_dest + 4 * num_word32 - 1, NULL, NULL) - EraseInitStruct.Sector + 1;
+    if (HAL_FLASHEx_Erase_IT(&EraseInitStruct) != HAL_OK) {
+        // error occurred during sector erase
+        HAL_FLASH_Lock(); // lock the flash
+        return;
+    }
+}
+*/
+
+void flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32) {
     // program the flash word by word
     for (int i = 0; i < num_word32; i++) {
         if (HAL_FLASH_Program(TYPEPROGRAM_WORD, flash_dest, *src) != HAL_OK) {
             // error occurred during flash write
+            HAL_FLASH_Lock(); // lock the flash
             return;
         }
         flash_dest += 4;
@@ -87,3 +120,47 @@ void flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32)
     // lock the flash
     HAL_FLASH_Lock();
 }
+
+/*
+ use erase, then write
+void flash_erase_and_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32) {
+    // check there is something to write
+    if (num_word32 == 0) {
+        return;
+    }
+
+    // unlock
+    HAL_FLASH_Unlock();
+
+    // Clear pending flags (if any)
+    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_EOP | FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR |
+                           FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR|FLASH_FLAG_PGSERR);
+
+    // erase the sector(s)
+    FLASH_EraseInitTypeDef EraseInitStruct;
+    EraseInitStruct.TypeErase = TYPEERASE_SECTORS;
+    EraseInitStruct.VoltageRange = VOLTAGE_RANGE_3; // voltage range needs to be 2.7V to 3.6V
+    EraseInitStruct.Sector = flash_get_sector_info(flash_dest, NULL, NULL);
+    EraseInitStruct.NbSectors = flash_get_sector_info(flash_dest + 4 * num_word32 - 1, NULL, NULL) - EraseInitStruct.Sector + 1;
+    uint32_t SectorError = 0;
+    if (HAL_FLASHEx_Erase(&EraseInitStruct, &SectorError) != HAL_OK) {
+        // error occurred during sector erase
+        HAL_FLASH_Lock(); // lock the flash
+        return;
+    }
+
+    // program the flash word by word
+    for (int i = 0; i < num_word32; i++) {
+        if (HAL_FLASH_Program(TYPEPROGRAM_WORD, flash_dest, *src) != HAL_OK) {
+            // error occurred during flash write
+            HAL_FLASH_Lock(); // lock the flash
+            return;
+        }
+        flash_dest += 4;
+        src += 1;
+    }
+
+    // lock the flash
+    HAL_FLASH_Lock();
+}
+*/

stmhal/flash.h

@@ -1,2 +1,3 @@
 uint32_t flash_get_sector_info(uint32_t addr, uint32_t *start_addr, uint32_t *size);
+void flash_erase(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32);
 void flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32);

stmhal/pybstdio.c

@@ -9,7 +9,6 @@
 #include "obj.h"
 #include "stream.h"
 #include "pybstdio.h"
-#include "storage.h"
 #include "usb.h"
 #include "usart.h"
 
@@ -50,9 +49,6 @@ int stdin_rx_chr(void) {
             return usart_rx_char(pyb_usart_global_debug);
         }
         __WFI();
-        if (storage_needs_flush()) {
-            storage_flush();
-        }
     }
 }
 

stmhal/pyexec.c

@@ -21,7 +21,6 @@
 #include "pybstdio.h"
 #include "readline.h"
 #include "pyexec.h"
-#include "storage.h"
 #include "usb.h"
 #include "build/py/py-version.h"
 

stmhal/stm32f4xx_it.c

@@ -49,6 +49,7 @@
 #include "obj.h"
 #include "exti.h"
 #include "timer.h"
+#include "storage.h"
 
 /** @addtogroup STM32F4xx_HAL_Examples
   * @{
@@ -263,6 +264,19 @@ void OTG_XX_WKUP_IRQHandler(void)
 {
 }*/
 
+// Handle a flash (erase/program) interrupt.
+void FLASH_IRQHandler(void) {
+    // This calls the real flash IRQ handler, if needed
+    /*
+    uint32_t flash_cr = FLASH->CR;
+    if ((flash_cr & FLASH_IT_EOP) || (flash_cr & FLASH_IT_ERR)) {
+        HAL_FLASH_IRQHandler();
+    }
+    */
+    // This call the storage IRQ handler, to check if the flash cache needs flushing
+    storage_irq_handler();
+}
+
 /**
   * @brief  These functions handle the EXTI interrupt requests.
   * @param  None

stmhal/storage.c

@@ -16,20 +16,22 @@
 #define FLASH_PART1_NUM_BLOCKS (224) // 16k+16k+16k+64k=112k
 #define FLASH_MEM_START_ADDR (0x08004000) // sector 1, 16k
 
+#define FLASH_FLAG_DIRTY        (1)
+#define FLASH_FLAG_FORCE_WRITE  (2)
+#define FLASH_FLAG_ERASED       (4)
 static bool flash_is_initialised = false;
-static bool flash_cache_dirty;
+static __IO uint8_t flash_flags = 0;
 static uint32_t flash_cache_sector_id;
 static uint32_t flash_cache_sector_start;
 static uint32_t flash_cache_sector_size;
 static uint32_t flash_tick_counter_last_write;
 
 static void flash_cache_flush(void) {
-    if (flash_cache_dirty) {
-        // sync the cache RAM buffer by writing it to the flash page
-        flash_write(flash_cache_sector_start, (const uint32_t*)CACHE_MEM_START_ADDR, flash_cache_sector_size / 4);
-        flash_cache_dirty = false;
-        // indicate a clean cache with LED off
-        led_state(PYB_LED_R1, 0);
+    if (flash_flags & FLASH_FLAG_DIRTY) {
+        flash_flags |= FLASH_FLAG_FORCE_WRITE;
+        while (flash_flags & FLASH_FLAG_DIRTY) {
+           NVIC->STIR = FLASH_IRQn;
+        }
     }
 }
 
@@ -44,9 +46,9 @@ static uint8_t *flash_cache_get_addr_for_write(uint32_t flash_addr) {
         flash_cache_sector_start = flash_sector_start;
         flash_cache_sector_size = flash_sector_size;
     }
-    flash_cache_dirty = true;
-    // indicate a dirty cache with LED on
-    led_state(PYB_LED_R1, 1);
+    flash_flags |= FLASH_FLAG_DIRTY;
+    led_state(PYB_LED_R1, 1); // indicate a dirty cache with LED on
+    flash_tick_counter_last_write = HAL_GetTick();
     return (uint8_t*)CACHE_MEM_START_ADDR + flash_addr - flash_sector_start;
 }
 
@@ -64,11 +66,17 @@ static uint8_t *flash_cache_get_addr_for_read(uint32_t flash_addr) {
 
 void storage_init(void) {
     if (!flash_is_initialised) {
-        flash_cache_dirty = false;
+        flash_flags = 0;
         flash_cache_sector_id = 0;
-        flash_is_initialised = true;
         flash_tick_counter_last_write = 0;
+        flash_is_initialised = true;
     }
+
+    // Enable the flash IRQ, which is used to also call our storage IRQ handler
+    // It needs to go at a higher priority than all those components that rely on
+    // the flash storage (eg higher than USB MSC).
+    HAL_NVIC_SetPriority(FLASH_IRQn, 1, 1);
+    HAL_NVIC_EnableIRQ(FLASH_IRQn);
 }
 
 uint32_t storage_get_block_size(void) {
@@ -79,9 +87,47 @@ uint32_t storage_get_block_count(void) {
     return FLASH_PART1_START_BLOCK + FLASH_PART1_NUM_BLOCKS;
 }
 
-bool storage_needs_flush(void) {
-    // wait 2 seconds after last write to flush
-    return flash_cache_dirty && sys_tick_has_passed(flash_tick_counter_last_write, 2000);
+void storage_irq_handler(void) {
+    if (!(flash_flags & FLASH_FLAG_DIRTY)) {
+        return;
+    }
+
+    // This code uses interrupts to erase the flash
+    /*
+    if (flash_erase_state == 0) {
+        flash_erase_it(flash_cache_sector_start, (const uint32_t*)CACHE_MEM_START_ADDR, flash_cache_sector_size / 4);
+        flash_erase_state = 1;
+        return;
+    }
+
+    if (flash_erase_state == 1) {
+        // wait for erase
+        // TODO add timeout
+        #define flash_erase_done() (__HAL_FLASH_GET_FLAG(FLASH_FLAG_BSY) == RESET)
+        if (!flash_erase_done()) {
+            return;
+        }
+        flash_erase_state = 2;
+    }
+    */
+
+    // This code erases the flash directly, waiting for it to finish
+    if (!(flash_flags & FLASH_FLAG_ERASED)) {
+        flash_erase(flash_cache_sector_start, (const uint32_t*)CACHE_MEM_START_ADDR, flash_cache_sector_size / 4);
+        flash_flags |= FLASH_FLAG_ERASED;
+        return;
+    }
+
+    // If not a forced write, wait at least 5 seconds after last write to flush
+    // On file close and flash unmount we get a forced write, so we can afford to wait a while
+    if ((flash_flags & FLASH_FLAG_FORCE_WRITE) || sys_tick_has_passed(flash_tick_counter_last_write, 5000)) {
+        // sync the cache RAM buffer by writing it to the flash page
+        flash_write(flash_cache_sector_start, (const uint32_t*)CACHE_MEM_START_ADDR, flash_cache_sector_size / 4);
+        // clear the flash flags now that we have a clean cache
+        flash_flags = 0;
+        // indicate a clean cache with LED off
+        led_state(PYB_LED_R1, 0);
+    }
 }
 
 void storage_flush(void) {
@@ -167,7 +213,6 @@ bool storage_write_block(const uint8_t *src, uint32_t block) {
         uint32_t flash_addr = FLASH_MEM_START_ADDR + (block - FLASH_PART1_START_BLOCK) * FLASH_BLOCK_SIZE;
         uint8_t *dest = flash_cache_get_addr_for_write(flash_addr);
         memcpy(dest, src, FLASH_BLOCK_SIZE);
-        flash_tick_counter_last_write = HAL_GetTick();
         return true;
 
     } else {

stmhal/storage.h

@@ -3,7 +3,7 @@
 void storage_init(void);
 uint32_t storage_get_block_size(void);
 uint32_t storage_get_block_count(void);
-bool storage_needs_flush(void);
+void storage_irq_handler(void);
 void storage_flush(void);
 bool storage_read_block(uint8_t *dest, uint32_t block);
 bool storage_write_block(const uint8_t *src, uint32_t block);

stmhal/timer.c

@@ -19,6 +19,7 @@
 // the interrupts to be dispatched, so they are all collected here.
 //
 // TIM3:
+//  - flash storage controller, to flush the cache
 //  - USB CDC interface, interval, to check for new data
 //  - LED 4, PWM to set the LED intensity
 //
@@ -29,14 +30,17 @@ TIM_HandleTypeDef TIM3_Handle;
 TIM_HandleTypeDef TIM5_Handle;
 TIM_HandleTypeDef TIM6_Handle;
 
+// Used to divide down TIM3 and periodically call the flash storage IRQ
+static uint32_t tim3_counter = 0;
+
 // TIM3 is set-up for the USB CDC interface
 void timer_tim3_init(void) {
     // set up the timer for USBD CDC
     __TIM3_CLK_ENABLE();
 
     TIM3_Handle.Instance = TIM3;
-    TIM3_Handle.Init.Period = (USBD_CDC_POLLING_INTERVAL*1000) - 1;
-    TIM3_Handle.Init.Prescaler = 84-1;
+    TIM3_Handle.Init.Period = (USBD_CDC_POLLING_INTERVAL*1000) - 1; // TIM3 fires every USBD_CDC_POLLING_INTERVAL ms
+    TIM3_Handle.Init.Prescaler = 84-1; // for System clock at 168MHz, TIM3 runs at 1MHz
     TIM3_Handle.Init.ClockDivision = 0;
     TIM3_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
     HAL_TIM_Base_Init(&TIM3_Handle);
@@ -105,6 +109,13 @@ void timer_tim6_init(uint freq) {
 void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
     if (htim == &TIM3_Handle) {
         USBD_CDC_HAL_TIM_PeriodElapsedCallback();
+
+        // Periodically raise a flash IRQ for the flash storage controller
+        if (tim3_counter++ >= 500 / USBD_CDC_POLLING_INTERVAL) {
+            tim3_counter = 0;
+            NVIC->STIR = FLASH_IRQn;
+        }
+
     } else if (htim == &TIM5_Handle) {
         servo_timer_irq_callback();
     }

stmhal/usbd_msc_storage.c

@@ -109,6 +109,12 @@ int8_t FLASH_STORAGE_StopUnit(uint8_t lun) {
     return 0;
 }
 
+int8_t FLASH_STORAGE_PreventAllowMediumRemoval(uint8_t lun, uint8_t param) {
+    // sync the flash so that the cache is cleared and the device can be unplugged/turned off
+    disk_ioctl(0, CTRL_SYNC, NULL);
+    return 0;
+}
+
 /**
   * @brief  Read data from the medium
   * @param  lun : logical unit number
@@ -146,7 +152,6 @@ int8_t FLASH_STORAGE_Write (uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16
         }
     }
     */
-    storage_flush(); // XXX hack for now so that the cache is always flushed
     return 0;
 }
 
@@ -165,6 +170,7 @@ const USBD_StorageTypeDef USBD_FLASH_STORAGE_fops = {
     FLASH_STORAGE_IsReady,
     FLASH_STORAGE_IsWriteProtected,
     FLASH_STORAGE_StopUnit,
+    FLASH_STORAGE_PreventAllowMediumRemoval,
     FLASH_STORAGE_Read,
     FLASH_STORAGE_Write,
     FLASH_STORAGE_GetMaxLun,
@@ -295,6 +301,10 @@ int8_t SDCARD_STORAGE_StopUnit(uint8_t lun) {
     return 0;
 }
 
+int8_t SDCARD_STORAGE_PreventAllowMediumRemoval(uint8_t lun, uint8_t param) {
+    return 0;
+}
+
 /**
   * @brief  Read data from the medium
   * @param  lun : logical unit number
@@ -340,6 +350,7 @@ const USBD_StorageTypeDef USBD_SDCARD_STORAGE_fops = {
     SDCARD_STORAGE_IsReady,
     SDCARD_STORAGE_IsWriteProtected,
     SDCARD_STORAGE_StopUnit,
+    SDCARD_STORAGE_PreventAllowMediumRemoval,
     SDCARD_STORAGE_Read,
     SDCARD_STORAGE_Write,
     SDCARD_STORAGE_GetMaxLun,

stmhal/usbdev/class/cdc_msc_hid/inc/usbd_cdc_msc_hid.h

@@ -54,6 +54,7 @@ typedef struct _USBD_STORAGE {
   int8_t (* IsReady) (uint8_t lun);
   int8_t (* IsWriteProtected) (uint8_t lun);
   int8_t (* StopUnit)(uint8_t lun);
+  int8_t (* PreventAllowMediumRemoval)(uint8_t lun, uint8_t param0);
   int8_t (* Read) (uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len);
   int8_t (* Write)(uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len);
   int8_t (* GetMaxLun)(void);

stmhal/usbdev/class/cdc_msc_hid/src/usbd_msc_scsi.c

@@ -472,6 +472,7 @@ static int8_t SCSI_AllowMediumRemoval(USBD_HandleTypeDef  *pdev, uint8_t lun, ui
 {
   USBD_MSC_BOT_HandleTypeDef  *hmsc = pdev->pClassData;   
   hmsc->bot_data_length = 0;
+  ((USBD_StorageTypeDef *)pdev->pUserData)->PreventAllowMediumRemoval(lun, params[0]);
   return 0;
 }