Add Real Time Clock (RTC) support for UFS device. This enhancement is
crucial for the internal maintenance operations of the UFS device. The
patch enables the device to handle both absolute and relative time
information. Furthermore, it includes periodic task to update the RTC in
accordance with the UFS Spec, ensuring the accuracy of RTC information for
the device's internal processes.

RTC and qTimestamp serve distinct purposes. The RTC provides a coarse level
of granularity with, at best, approximate single-second resolution. This
makes the RTC well-suited for the device to determine the approximate age
of programmed blocks after being updated by the host. On the other hand,
qTimestamp offers nanosecond granularity and is specifically designed for
synchronizing Device Error Log entries with corresponding host-side logs.

Given that the RTC has been a standard feature since UFS Spec 2.0, and
qTimestamp was introduced in UFS Spec 4.0, the majority of UFS devices
currently on the market rely on RTC. Therefore, it is advisable to continue
supporting RTC in the Linux kernel. This ensures compatibility with the
prevailing UFS device implementations and facilitates seamless integration
with existing hardware.  By maintaining support for RTC, we ensure broad
compatibility and avoid potential issues arising from deviations in device
specifications across different UFS versions.
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Mike Bi <mikebi@micron.com>
Signed-off-by: Luca Porzio <lporzio@micron.com>
Link: https://lore.kernel.org/r/20231212220825.85255-3-beanhuo@iokpp.deAcked-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>