The loops waiting for the card to leave its busy state started their yield
backoff at 100 ms. A card is typically busy for a few milliseconds after a
write, so the backoff never fired and every write was followed by hundreds
of back-to-back CMD13 commands. Occupying the host controller like this
slows down unrelated work on both cores, not just the calling task.
Delay between polls instead, starting at CONFIG_SD_READY_POLL_PERIOD_START_US
(100 us) and doubling. Both the delay and the configured start period are
capped at one FreeRTOS tick period, where vTaskDelay() already yields and one
command per tick is not a storm. A typical wait now costs a handful of
commands instead of hundreds.
Applies to sdmmc_wait_for_idle(), sdmmc_init_sd_wait_data_ready() and
read_tuning_block().
Closes https://github.com/espressif/esp-idf/issues/19034
Adam Múdry
C.S.M
sonika.rathi
armando
Ivan Grokhotkov