Provide a function to the MMC hosts to read some blocks of data as part
of their tuning. The card parameter is optional since it is not
available from the execute_tuning() operation, but present in
execute_hs400_tuning() and prepare_sd_hs_tuning().

This function only returns the status of the read operation, not the
data read.

Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
---
 drivers/mmc/core/mmc_ops.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mmc/host.h   |  2 ++
 2 files changed, 81 insertions(+)

diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index 66283825513cb4ff993a1b2ec1f0b0cac4e74487..d29e5daf3e326ab37e61c99456421b1f66bcb0de 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -1077,3 +1077,82 @@ int mmc_sanitize(struct mmc_card *card, unsigned int timeout_ms)
 	return err;
 }
 EXPORT_SYMBOL_GPL(mmc_sanitize);
+
+/**
+ * mmc_read_tuning() - read data blocks from the mmc
+ * @card: mmc card to read from, can be NULL
+ * @host: mmc host doing the read
+ * @blksz: data block size
+ * @blocks: number of blocks to read
+ *
+ * Read one or more blocks of data from the beginning of the mmc. This is a
+ * low-level helper for tuning operation. If card is NULL, it is assumed that
+ * CMD23 can be used for multi-block read.
+ *
+ * Note: Allocate and free a temporary buffer to store the data read. The data
+ * is not available outside of the function, only the status of the read
+ * operation.
+ *
+ * Return: 0 in case of success, otherwise -EIO / -ENOMEM / -E2BIG
+ */
+int mmc_read_tuning(struct mmc_card *card, struct mmc_host *host,
+		    unsigned int blksz, unsigned int blocks)
+{
+	struct mmc_request mrq = {};
+	struct mmc_command sbc = {};
+	struct mmc_command cmd = {};
+	struct mmc_command stop = {};
+	struct mmc_data data = {};
+	struct scatterlist sg;
+	void *buf;
+	unsigned int len;
+
+	if (blocks > 1) {
+		if (mmc_host_can_cmd23(host) &&
+		    (!card || (mmc_card_can_cmd23(card) &&
+		     !mmc_card_blk_no_cmd23(card)))) {
+			mrq.sbc = &sbc;
+			sbc.opcode = MMC_SET_BLOCK_COUNT;
+			sbc.arg = blocks;
+			sbc.flags = MMC_RSP_R1 | MMC_CMD_AC;
+		}
+		cmd.opcode = MMC_READ_MULTIPLE_BLOCK;
+		mrq.stop = &stop;
+		stop.opcode = MMC_STOP_TRANSMISSION;
+		stop.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
+	} else {
+		cmd.opcode = MMC_READ_SINGLE_BLOCK;
+	}
+
+	mrq.cmd = &cmd;
+	cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
+
+	mrq.data = &data;
+	data.flags = MMC_DATA_READ;
+	data.blksz = blksz;
+	data.blocks = blocks;
+	data.blk_addr = 0;
+	data.sg = &sg;
+	data.sg_len = 1;
+	if (card)
+		mmc_set_data_timeout(&data, card);
+	else
+		data.timeout_ns = 1000000000;
+
+	if (check_mul_overflow(blksz, blocks, &len))
+		return -E2BIG;
+	buf = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	sg_init_one(&sg, buf, len);
+
+	mmc_wait_for_req(host, &mrq);
+	kfree(buf);
+
+	if (sbc.error || cmd.error || data.error)
+		return -EIO;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mmc_read_tuning);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 68f09a955a902047ac517441b6820fa6e4166a13..5a6471a6219222b199a16afd9e6bd5ab74b05c86 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -743,5 +743,7 @@ int mmc_send_status(struct mmc_card *card, u32 *status);
 int mmc_send_tuning(struct mmc_host *host, u32 opcode, int *cmd_error);
 int mmc_send_abort_tuning(struct mmc_host *host, u32 opcode);
 int mmc_get_ext_csd(struct mmc_card *card, u8 **new_ext_csd);
+int mmc_read_tuning(struct mmc_card *card, struct mmc_host *host,
+		    unsigned int blksz, unsigned int blocks);
 
 #endif /* LINUX_MMC_HOST_H */

-- 
2.50.1

On Wed, 16 Jul 2025 at 17:47, Benoît Monin <benoit.monin@bootlin.com> wrote:
>
> Provide a function to the MMC hosts to read some blocks of data as part
> of their tuning. The card parameter is optional since it is not
> available from the execute_tuning() operation, but present in
> execute_hs400_tuning() and prepare_sd_hs_tuning().
>
> This function only returns the status of the read operation, not the
> data read.
>
> Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
> ---
>  drivers/mmc/core/mmc_ops.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mmc/host.h   |  2 ++
>  2 files changed, 81 insertions(+)
>
> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
> index 66283825513cb4ff993a1b2ec1f0b0cac4e74487..d29e5daf3e326ab37e61c99456421b1f66bcb0de 100644
> --- a/drivers/mmc/core/mmc_ops.c
> +++ b/drivers/mmc/core/mmc_ops.c
> @@ -1077,3 +1077,82 @@ int mmc_sanitize(struct mmc_card *card, unsigned int timeout_ms)
>         return err;
>  }
>  EXPORT_SYMBOL_GPL(mmc_sanitize);
> +
> +/**
> + * mmc_read_tuning() - read data blocks from the mmc
> + * @card: mmc card to read from, can be NULL
> + * @host: mmc host doing the read
> + * @blksz: data block size
> + * @blocks: number of blocks to read
> + *
> + * Read one or more blocks of data from the beginning of the mmc. This is a
> + * low-level helper for tuning operation. If card is NULL, it is assumed that
> + * CMD23 can be used for multi-block read.

It makes sense to have a comment for this, but I would just just drop
the "struct mmc_card *card" as an in-parameter. If it turns out to be
needed later on, we would need additional changes to enable the caller
of mmc_read_tuning() to pass the "card" along.

> + *
> + * Note: Allocate and free a temporary buffer to store the data read. The data
> + * is not available outside of the function, only the status of the read
> + * operation.
> + *
> + * Return: 0 in case of success, otherwise -EIO / -ENOMEM / -E2BIG
> + */
> +int mmc_read_tuning(struct mmc_card *card, struct mmc_host *host,
> +                   unsigned int blksz, unsigned int blocks)
> +{
> +       struct mmc_request mrq = {};
> +       struct mmc_command sbc = {};
> +       struct mmc_command cmd = {};
> +       struct mmc_command stop = {};
> +       struct mmc_data data = {};
> +       struct scatterlist sg;
> +       void *buf;
> +       unsigned int len;
> +
> +       if (blocks > 1) {
> +               if (mmc_host_can_cmd23(host) &&
> +                   (!card || (mmc_card_can_cmd23(card) &&
> +                    !mmc_card_blk_no_cmd23(card)))) {
> +                       mrq.sbc = &sbc;
> +                       sbc.opcode = MMC_SET_BLOCK_COUNT;
> +                       sbc.arg = blocks;
> +                       sbc.flags = MMC_RSP_R1 | MMC_CMD_AC;
> +               }
> +               cmd.opcode = MMC_READ_MULTIPLE_BLOCK;
> +               mrq.stop = &stop;
> +               stop.opcode = MMC_STOP_TRANSMISSION;
> +               stop.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
> +       } else {
> +               cmd.opcode = MMC_READ_SINGLE_BLOCK;
> +       }
> +
> +       mrq.cmd = &cmd;
> +       cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
> +
> +       mrq.data = &data;
> +       data.flags = MMC_DATA_READ;
> +       data.blksz = blksz;
> +       data.blocks = blocks;
> +       data.blk_addr = 0;
> +       data.sg = &sg;
> +       data.sg_len = 1;
> +       if (card)
> +               mmc_set_data_timeout(&data, card);
> +       else
> +               data.timeout_ns = 1000000000;
> +
> +       if (check_mul_overflow(blksz, blocks, &len))
> +               return -E2BIG;
> +       buf = kmalloc(len, GFP_KERNEL);
> +       if (!buf)
> +               return -ENOMEM;
> +
> +       sg_init_one(&sg, buf, len);
> +
> +       mmc_wait_for_req(host, &mrq);
> +       kfree(buf);
> +
> +       if (sbc.error || cmd.error || data.error)
> +               return -EIO;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(mmc_read_tuning);
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 68f09a955a902047ac517441b6820fa6e4166a13..5a6471a6219222b199a16afd9e6bd5ab74b05c86 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -743,5 +743,7 @@ int mmc_send_status(struct mmc_card *card, u32 *status);
>  int mmc_send_tuning(struct mmc_host *host, u32 opcode, int *cmd_error);
>  int mmc_send_abort_tuning(struct mmc_host *host, u32 opcode);
>  int mmc_get_ext_csd(struct mmc_card *card, u8 **new_ext_csd);
> +int mmc_read_tuning(struct mmc_card *card, struct mmc_host *host,
> +                   unsigned int blksz, unsigned int blocks);
>
>  #endif /* LINUX_MMC_HOST_H */
>
> --
> 2.50.1
>

Otherwise this looks good to me!

Kind regards
Uffe