This series introduces the MHI PHC (PTP Hardware Clock) driver, which
registers a PTP (Precision Time Protocol) clock and communicates with
the MHI core to get the device side timestamps. These timestamps are
then exposed to the PTP subsystem, enabling precise time synchronization
between the host and the device.

The device exposes these through MHI time sync capability registers.

The following diagram illustrates the architecture and data flow:

 +-------------+    +--------------------+    +--------------+
 |Userspace App|<-->|Kernel PTP framework|<-->|MHI PHC Driver|
 +-------------+    +--------------------+    +--------------+
                                                     |
                                                     v
 +-------------------------------+         +-----------------+
 | MHI Device (Timestamp source) |<------->| MHI Core Driver |
 +-------------------------------+         +-----------------+

- User space applications use the standard Linux PTP interface.
- The PTP subsystem routes IOCTLs to the MHI PHC driver.
- The MHI PHC driver communicates with the MHI core to fetch timestamps.
- The MHI core interacts with the device to retrieve accurate time data.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
Changes in V2:
- Rebases to the latest code.
- Patch 1 (bus: mhi: host: Add support to read MHI capabilities) which
is dependent change was brought it here as the series which this patch
is part need to re-designed and will take time https://lore.kernel.org/all/CAFEp6-0ik4B20cRyid9w0f+UgibGciPof9HCWTJ=uBOPvHG35Q@mail.gmail.com/.
- Link to v1: https://lore.kernel.org/all/20250818-tsc_time_sync-v1-0-2747710693ba@oss.qualcomm.com/

---
Imran Shaik (1):
      bus: mhi: host: mhi_phc: Add support for PHC over MHI

Krishna Chaitanya Chundru (3):
      bus: mhi: host: Add support for 64bit register reads and writes
      bus: mhi: pci_generic: Add support for 64 bit register read & write
      bus: mhi: host: Update the Time sync logic to read 64 bit register value

Vivek Pernamitta (2):
      bus: mhi: host: Add support to read MHI capabilities
      bus: mhi: host: Add support for non-posted TSC timesync feature

 drivers/bus/mhi/common.h           |  15 ++++
 drivers/bus/mhi/host/Kconfig       |   8 ++
 drivers/bus/mhi/host/Makefile      |   1 +
 drivers/bus/mhi/host/init.c        |  60 +++++++++++++++
 drivers/bus/mhi/host/internal.h    |   9 +++
 drivers/bus/mhi/host/main.c        |  97 ++++++++++++++++++++++++
 drivers/bus/mhi/host/mhi_phc.c     | 150 +++++++++++++++++++++++++++++++++++++
 drivers/bus/mhi/host/mhi_phc.h     |  28 +++++++
 drivers/bus/mhi/host/pci_generic.c |  46 ++++++++++++
 include/linux/mhi.h                |  43 +++++++++++
 10 files changed, 457 insertions(+)
---
base-commit: e774d5f1bc27a85f858bce7688509e866f8e8a4e
change-id: 20260411-tsc_timesync-f877a0394393

Best regards,
-- 
Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>

On Sat, 11 Apr 2026 13:42:00 +0530 Krishna Chaitanya Chundru wrote:
> - User space applications use the standard Linux PTP interface.
> - The PTP subsystem routes IOCTLs to the MHI PHC driver.
> - The MHI PHC driver communicates with the MHI core to fetch timestamps.
> - The MHI core interacts with the device to retrieve accurate time data.

Nack, stop adding functionality under the mhi "bus".
Bus is supposed to be an abstraction into which real drivers plug in.

On Sun, Apr 12, 2026 at 08:09:51AM -0700, Jakub Kicinski wrote:
> On Sat, 11 Apr 2026 13:42:00 +0530 Krishna Chaitanya Chundru wrote:
> > - User space applications use the standard Linux PTP interface.
> > - The PTP subsystem routes IOCTLs to the MHI PHC driver.
> > - The MHI PHC driver communicates with the MHI core to fetch timestamps.
> > - The MHI core interacts with the device to retrieve accurate time data.

This is a misleading statement. Only the 'pci_generic' controller driver interacts
with the device for querying timestamp. MHI bus just acts as a messenger.

> 
> Nack, stop adding functionality under the mhi "bus".
> Bus is supposed to be an abstraction into which real drivers plug in.

MHI bus is very similar to the PCI bus. Just like PCI capabilities, MHI also has
capabilities to discover the supported functionalities including timesync. So
for making use of the timesync feature, we need to add some hooks into the MHI
bus layer, but the functionality is added to the separate driver,
'drivers/bus/mhi/host/mhi_phc*'. This is also quite similar to how PCI(e)
features like AER, hotplug are structured.

In this series, timesync API definitions are added mistakenly to the core bus
code, which should be moved to the mhi_phc driver instead.

- Mani

-- 
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