Re: [PATCH] mmc: core: Add support for the eMMC RTC feature in mmc_ops

On Tue, Dec 07, 2021 at 08:28:42AM +0000, Avri Altman wrote:

quoted

This patch adds support to set the RTC information in
the eMMC device. This is based on the JEDEC specification.

There is no way however, to read the RTC time from the
device. Hence we rely on the response of the CMD49 to
confirm the completion of the operation.

This patch has been tested successfully with the ioctl
interface. This patch has also been tested suceessfully
with all the three RTC_INFO_TYPEs.

If this is triggered from user-space via ioctl anyway,
Why do we need this command to be implemented in the kernel?
Why not just add this to mmc-utils?

Thanks,
Avri

As per the spec, B51: Section 6.6.35:
Providing RTC info may be useful for internal maintainance operations.
And the host should send it on the following events:
- power-up
- wake-up
- Periodically
Hence IMO, the Kernel would be the right place of peforming this
operation.

Thanks for the response,
Nisha

quoted

Signed-off-by: Nishad Kamdar <redacted>
---
 drivers/mmc/core/mmc_ops.c | 59
++++++++++++++++++++++++++++++++++++++
 drivers/mmc/core/mmc_ops.h |  2 ++
 include/linux/mmc/mmc.h    |  1 +
 3 files changed, 62 insertions(+)

diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index d63d1c735335..490372341b3b 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c

@@ -1063,3 +1063,62 @@ int mmc_sanitize(struct mmc_card *card,

unsigned int timeout_ms)
        return err;
 }
 EXPORT_SYMBOL_GPL(mmc_sanitize);
+
+int mmc_set_time(struct mmc_card *card, struct mmc_host *host,
+                u8 rtc_info_type, u64 seconds)
+{
+       struct mmc_request mrq = {};
+       struct mmc_command cmd = {};
+       struct mmc_data data = {};
+       struct scatterlist sg;
+       int err = 0;
+       u8 *data_buf;
+
+       data_buf = kzalloc(512, GFP_KERNEL);
+       if (!data_buf)
+               return -ENOMEM;
+
+       if (rtc_info_type == 0x01 || rtc_info_type == 0x02 ||
+           rtc_info_type == 0x03) {
+               data_buf[0] = 0x01;
+               data_buf[1] = rtc_info_type;
+               memcpy(&data_buf[2], &seconds, sizeof(u64));
+       } else {
+               pr_err("%s: invalid rtc_info_type %d\n",
+                      mmc_hostname(host), rtc_info_type);
+               kfree(data_buf);
+               return -EINVAL;
+       }
+
+       mrq.cmd = &cmd;
+       mrq.data = &data;
+
+       cmd.opcode = MMC_SET_TIME;
+       cmd.arg = 0;
+       cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
+
+       data.blksz = 512;
+       data.blocks = 1;
+       data.flags = MMC_DATA_WRITE;
+       data.sg = &sg;
+       data.sg_len = 1;
+       sg_init_one(&sg, data_buf, 512);
+
+       mmc_set_data_timeout(&data, card);
+
+       mmc_wait_for_req(host, &mrq);
+
+       if (cmd.error) {
+               err = cmd.error;
+               goto out;
+       }
+
+       if (data.error) {
+               err = data.error;
+               goto out;
+       }
+out:
+       kfree(data_buf);
+       return err;
+}
+EXPORT_SYMBOL_GPL(mmc_set_time);

diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 9c813b851d0b..0c8695d1b363 100644
--- a/drivers/mmc/core/mmc_ops.h
+++ b/drivers/mmc/core/mmc_ops.h

@@ -55,6 +55,8 @@ void mmc_run_bkops(struct mmc_card *card);
 int mmc_cmdq_enable(struct mmc_card *card);
 int mmc_cmdq_disable(struct mmc_card *card);
 int mmc_sanitize(struct mmc_card *card, unsigned int timeout_ms);
+int mmc_set_time(struct mmc_card *card, struct mmc_host *host,
+                u8 rtc_info_type, u64 seconds);

 #endif

diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
index d9a65c6a8816..52a3bf873d50 100644
--- a/include/linux/mmc/mmc.h
+++ b/include/linux/mmc/mmc.h

@@ -64,6 +64,7 @@
 #define MMC_WRITE_MULTIPLE_BLOCK 25   /* adtc                    R1  */
 #define MMC_PROGRAM_CID          26   /* adtc                    R1  */
 #define MMC_PROGRAM_CSD          27   /* adtc                    R1  */
+#define MMC_SET_TIME            49   /* adtc                    R1  */

   /* class 6 */
 #define MMC_SET_WRITE_PROT       28   /* ac   [31:0] data addr   R1b */
--

2.17.1