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spi_flash: Remove 16KB free internal heap limit for esp_flash_read() into PSRAM

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Allocation of the temporary internal buffer will now repeat until a small enough buffer can be
allocated, and only fail if less than a 256 byte block of internal RAM is free.

Adds unit test for the same, and generic test utility for creating memory pressure.
This commit is contained in:
Angus Gratton
2020-02-27 11:57:00 +11:00
committed by Angus Gratton
parent af4c6ac0f3
commit c38c3ff3f0
4 changed files with 136 additions and 18 deletions
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28
components/spi_flash/esp_flash_api.c
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@@ -497,11 +497,25 @@ esp_err_t IRAM_ATTR esp_flash_read(esp_flash_t *chip, void *buffer, uint32_t add
bool direct_read = chip->host->supports_direct_read(chip->host, buffer);
uint8_t* temp_buffer = NULL;
//each time, we at most read this length
//after that, we release the lock to allow some other operations
size_t read_chunk_size = MIN(MAX_READ_CHUNK, length);
if (!direct_read) {
uint32_t length_to_allocate = MIN(MAX_READ_CHUNK, length);
length_to_allocate = (length_to_allocate+3)&(~3);
temp_buffer = heap_caps_malloc(length_to_allocate, MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
ESP_LOGV(TAG, "allocate temp buffer: %p (%d)", temp_buffer, length_to_allocate);
/* Allocate temporary internal buffer to use for the actual read. If the preferred size
doesn't fit in free internal memory, allocate the largest available free block.
(May need to shrink read_chunk_size and retry due to race conditions with other tasks
also allocating from the heap.)
*/
unsigned retries = 5;
while(temp_buffer == NULL && retries--) {
read_chunk_size = MIN(read_chunk_size, heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT));
read_chunk_size = (read_chunk_size + 3) & ~3;
temp_buffer = heap_caps_malloc(read_chunk_size, MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
}
ESP_LOGV(TAG, "allocate temp buffer: %p (%d)", temp_buffer, read_chunk_size);
if (temp_buffer == NULL) {
return ESP_ERR_NO_MEM;
}
@@ -516,9 +530,9 @@ esp_err_t IRAM_ATTR esp_flash_read(esp_flash_t *chip, void *buffer, uint32_t add
}
//if required (dma buffer allocated), read to the buffer instead of the original buffer
uint8_t* buffer_to_read = (temp_buffer)? temp_buffer : buffer;
//each time, we at most read this length
//after that, we release the lock to allow some other operations
uint32_t length_to_read = MIN(MAX_READ_CHUNK, length);
// Length we will read this iteration is either the chunk size or the remaining length, whichever is smaller
size_t length_to_read = MIN(read_chunk_size, length);
if (err == ESP_OK) {
err = chip->chip_drv->read(chip, buffer_to_read, address, length_to_read);