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

[Nishad Kamdar <nishadkamdar@gmail.com>]

On Tue, Dec 07, 2021 at 08:28:42AM +0000, Avri Altman wrote:
>  
> > 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
> > 
> > Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
> > ---
> >  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
>