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sdmmc: add more comments about card initialization steps

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This commit is contained in:
Ivan Grokhotkov 2017-07-12 21:17:51 +08:00
parent 6baf8195ee
commit 14c96838bf
1 changed files with 27 additions and 1 deletions
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28
components/sdmmc/sdmmc_cmd.c
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@ -130,12 +130,15 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
}
}
ESP_LOGD(TAG, "host_ocr=0x%x card_ocr=0x%x", host_ocr, card->ocr);
/* Clear all voltage bits in host's OCR which the card doesn't support.
* Don't touch CCS bit because in SPI mode cards don't report CCS in ACMD41
* response.
*/
host_ocr &= (card->ocr | (~SD_OCR_VOL_MASK));
ESP_LOGD(TAG, "sdmmc_card_init: host_ocr=%08x, card_ocr=%08x", host_ocr, card->ocr);
/* Read and decode the contents of CID register */
if (!is_spi) {
err = sddmc_send_cmd_all_send_cid(card, &card->cid);
if (err != ESP_OK) {
@ -155,6 +158,7 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
}
}
/* Get and decode the contents of CSD register. Determine card capacity. */
err = sdmmc_send_cmd_send_csd(card, &card->csd);
if (err != ESP_OK) {
ESP_LOGE(TAG, "%s: send_csd (1) returned 0x%x", __func__, err);
@ -167,6 +171,11 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
__func__, card->csd.capacity, max_sdsc_capacity);
card->csd.capacity = max_sdsc_capacity;
}
/* Switch the card from stand-by mode to data transfer mode (not needed if
* SPI interface is used). This is needed to issue SET_BLOCKLEN and
* SEND_SCR commands.
*/
if (!is_spi) {
err = sdmmc_send_cmd_select_card(card, card->rca);
if (err != ESP_OK) {
@ -174,6 +183,11 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
return err;
}
}
/* SDSC cards support configurable data block lengths.
* We don't use this feature and set the block length to 512 bytes,
* same as the block length for SDHC cards.
*/
if ((card->ocr & SD_OCR_SDHC_CAP) == 0) {
err = sdmmc_send_cmd_set_blocklen(card, &card->csd);
if (err != ESP_OK) {
@ -181,11 +195,21 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
return err;
}
}
/* Get the contents of SCR register: bus width and the version of SD spec
* supported by the card.
* In SD mode, this is the first command which uses D0 line. Errors at
* this step usually indicate connection issue or lack of pull-up resistor.
*/
err = sdmmc_send_cmd_send_scr(card, &card->scr);
if (err != ESP_OK) {
ESP_LOGE(TAG, "%s: send_scr returned 0x%x", __func__, err);
ESP_LOGE(TAG, "%s: send_scr (1) returned 0x%x", __func__, err);
return err;
}
/* If the host has been initialized with 4-bit bus support, and the card
* supports 4-bit bus, switch to 4-bit bus now.
*/
if ((config->flags & SDMMC_HOST_FLAG_4BIT) &&
(card->scr.bus_width & SCR_SD_BUS_WIDTHS_4BIT)) {
ESP_LOGD(TAG, "switching to 4-bit bus mode");
@ -206,6 +230,8 @@ esp_err_t sdmmc_card_init(const sdmmc_host_t* config, sdmmc_card_t* card)
return err;
}
}
/* Wait for the card to be ready for data transfers */
uint32_t status = 0;
while (!host_is_spi(card) && !(status & MMC_R1_READY_FOR_DATA)) {
// TODO: add some timeout here