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mmc: mmc_spi: multiple block read remove read crc ack

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commit fef12d9f5bcf7e2b19a7cf1295c6abd5642dd241 upstream.

For multiple block read, the current implementation, transfer packet
includes cmd53 + cmd53 response + block nums*(1byte token +
block length bytes payload + 2bytes CRC + 1byte transfer), the last
1byte transfer of every block is not needed, so remove it.

Why doesn't multiple block read need CRC ack?
For read operation, host side get the payload and CRC value, then
will only check the CRC value to confirm if the data is correct or
not, but not send CRC ack to card. If the data is correct, save it,
or discard it and retransmit if data is error, so the last 1byte
transfer of every block make no sense.

What's the side effect of this 1byte transfer?
As the SPI is full duplex, if add this redundant 1byte transfer, SDIO
card side take it as the token of next block, then all the next sub
blocks sequence distort.

Signed-off-by: Rex Chen <rex.chen_1@nxp.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250728082230.1037917-3-rex.chen_1@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rex Chen
2025-07-28 17:22:30 +09:00
committed by Greg Kroah-Hartman
parent e58bb2cab7
commit b322ea3114
1 changed files with 1 additions and 1 deletions
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2
drivers/mmc/host/mmc_spi.c
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@@ -563,7 +563,7 @@ mmc_spi_setup_data_message(struct mmc_spi_host *host, bool multiple, bool write)
* the next token (next data block, or STOP_TRAN). We can try to
* minimize I/O ops by using a single read to collect end-of-busy.
*/
if (multiple || write) {
if (write) {
t = &host->early_status;
memset(t, 0, sizeof(*t));
t->len = write ? sizeof(scratch->status) : 1;