Command response tokens can be delayed from the original command by 1
to 8 bytes. In 4a2489b9, handling for delayed tokens was added for
normal (no data) commands, and data read commands. This adds handling
for delayed commands for data write commands.
- In SPI mode, the card will respond to the initial SDIO reset (done
using CMD52) with “invalid command” error. Handle this correctly.
- sdmmc_card_init had a hack where GO_IDLE_STATE (CMD0) command was
sent twice. Add explanation why this is done, and don’t expect
correct response from the card on first CMD0.
- improve logs printed at debug level by adding CMD index
SDSPI driver optimized polling of the response tokens by requesting
two extra bytes on top of the block size (512) and CRC (2), and
checking whether these bytes contained the data response token or
not. In case the token was there, further polling would not need to
happen, thereby reducing latency between two consecutive blocks
transferred. However this caused compatibility issues when these two
extra bytes were sent after reading the final block. When
STOP_TRANSMISSION command was sent, these extra two bytes were
treated as part of the command, causing an invalid command error.
This fixes the logic by only requesting extra two bytes if the block
being read is not the final block. In addition to that, more strict
error checking is implemented for command response tokens.
Previously SDSPI host driver would rely on retry count when waiting for
the card to read or write data. This caused different timeout times
depending on CPU frequency and card clock frequency. In practice, card
performance does not depend on these two factors.
This change uses timeout_ms field of sdmmc_command_t introduced
previously for SDMMC host.
Fixes https://esp32.com/viewtopic.php?f=2&t=3440&p=16037 and similar
issues related to SDSPI timeouts.
Anton Maklakov